U.S. patent application number 14/257698 was filed with the patent office on 2015-04-16 for extraction and sequestration of carbon dioxide.
This patent application is currently assigned to Kilimanjaro Energy, Inc.. The applicant listed for this patent is Kilimanjaro Energy, Inc.. Invention is credited to Klaus S. Lackner, Allen B. Wright.
Application Number | 20150104554 14/257698 |
Document ID | / |
Family ID | 40986184 |
Filed Date | 2015-04-16 |
United States Patent
Application |
20150104554 |
Kind Code |
A1 |
Wright; Allen B. ; et
al. |
April 16, 2015 |
EXTRACTION AND SEQUESTRATION OF CARBON DIOXIDE
Abstract
The present disclosure provides a method and apparatus for
extracting carbon dioxide (CO.sub.2) from a fluid stream and for
delivering that extracted CO.sub.2 to controlled environments for
utilization by a secondary process. Various extraction and delivery
methods are disclosed specific to certain secondary uses, included
the attraction of CO.sub.2 sensitive insects, the ripening and
preservation of produce, and the neutralization of brine.
Inventors: |
Wright; Allen B.; (Tucson,
AZ) ; Lackner; Klaus S.; (Dobbs Ferry, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kilimanjaro Energy, Inc. |
San Francisco |
CA |
US |
|
|
Assignee: |
Kilimanjaro Energy, Inc.
San Francisco
CA
|
Family ID: |
40986184 |
Appl. No.: |
14/257698 |
Filed: |
April 21, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13737818 |
Jan 9, 2013 |
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14257698 |
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12389213 |
Feb 19, 2009 |
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13737818 |
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61029831 |
Feb 19, 2008 |
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61074972 |
Jun 23, 2008 |
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61079776 |
Jul 10, 2008 |
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Current U.S.
Class: |
426/419 ;
119/200; 422/122; 423/220; 423/437.1; 43/2; 705/317; 96/143;
96/145; 96/4 |
Current CPC
Class: |
B01D 2259/4009 20130101;
B01D 2257/402 20130101; B01D 53/1475 20130101; B65D 88/745
20130101; Y02C 20/40 20200801; A01K 67/033 20130101; B01D 53/02
20130101; B01D 53/22 20130101; B01D 53/62 20130101; B01D 2252/204
20130101; B01D 2257/302 20130101; Y02P 20/151 20151101; B01D 53/96
20130101; B01D 53/0462 20130101; G06Q 30/018 20130101; Y02C 10/08
20130101; Y02P 20/152 20151101; B01D 61/445 20130101; A01N 59/04
20130101; A01M 1/023 20130101; B01D 2252/103 20130101; B01D
2253/102 20130101; Y02C 20/10 20130101; B01D 2259/4145 20130101;
Y02C 10/10 20130101; B01D 2257/404 20130101; C01B 32/50 20170801;
Y02P 20/153 20151101; B01D 2252/00 20130101; B01D 2253/206
20130101; B01D 2259/40086 20130101; B01D 2257/504 20130101; Y02C
10/04 20130101 |
Class at
Publication: |
426/419 ;
422/122; 423/437.1; 423/220; 96/143; 96/145; 96/4; 43/2; 119/200;
705/317 |
International
Class: |
B01D 53/62 20060101
B01D053/62; B01D 53/14 20060101 B01D053/14; B01D 53/02 20060101
B01D053/02; G06Q 30/00 20060101 G06Q030/00; B01D 53/22 20060101
B01D053/22; B65D 88/74 20060101 B65D088/74; A01M 1/02 20060101
A01M001/02; A01K 67/033 20060101 A01K067/033; C01B 31/20 20060101
C01B031/20; B01D 53/96 20060101 B01D053/96 |
Claims
1. A system for removing carbon dioxide from a fluid, comprising
passing a stream of the fluid in contact with a sorbent to absorb
and concentrate carbon dioxide from the fluid stream; releasing the
carbon dioxide from the sorbent; and delivering the carbon dioxide
for use in a secondary process.
2. The system of claim 1, wherein the carbon dioxide is delivered
to the secondary process in a gaseous state, solid state, or liquid
state, as described.
3. The system of claim 1, wherein the secondary process is selected
from a group consisting of: machining coolant and lubricant, grit
blasting, for smoothing or paint or rust removal, cryogenic
cleaning, quick freeze processes, R744 refrigerant, dry-cleaning
solvent, perishable shipping container pre-cooling, perishable
shipping inert environment maintenance, beverage carbonation, fire
suppression, plant fertilization, horticulture, agriculture,
silvaculture, aquatic algae production, enhanced oil recovery,
water softening, Solvay process, propellant, pressurizing gas, e.g.
for aerosol cans, inflation gas, e.g. for life rafts, supercritical
CO.sub.2 extraction, semi conductor manufacturing, organic solvent,
perfume aromatics, decaffeinating coffee or tea, supramics,
pharmaceutical manufacturing, chemical production of urea,
methanol, inorganic carbonates, organic carbonates, polyurethanes,
paint pigments, foaming agents, carbon based fuels, synthetic
fuels, fumigation of farm products, neutralization of alkaline
waters or slurries or solid materials, and gas shields for welding
or electronics manufacturing.
4. The system of claim 1, wherein the sorbent is an ion exchange
membrane material.
5. The system of claim 1, wherein the carbon dioxide is released
from the sorbent by exposing the sorbent to increased humidity, by
using water, humid air, or pulses of steam.
6. The system of claim 1, wherein the carbon dioxide is released
from the sorbent using a weak liquid amine as a secondary
sorbent.
7. The method of claim 1, wherein the sorbent is a resin, and
wherein the carbon dioxide is released from the sorbent utilizing a
humidity swing, and wherein the resin is contained in a chamber
that also contains activated carbon, further comprising the step of
drying out the activated carbon to capture the carbon dioxide in a
concentrated form prior to delivering the carbon dioxide for use in
a secondary process.
8. The method of claim 1, wherein the carbon dioxide is released
from the sorbent by washing the sorbent with a wash fluid to create
an effluent, placing the effluent on the acid side of an
electrodialysis cell, driving the pH of the acid side of the
electrodialysis cell to a neutral pH to release carbon dioxide,
prior to delivering the carbon dioxide for use in a secondary
process.
9. A method for removing carbon dioxide from a gas, comprising:
bringing said gas in contact with a resin contained in a plurality
of chambers, wherein a plurality of chambers are connected in
series; wetting said resin with water, wherein the water enters a
first chamber and exits through a last chamber; collecting water
vapor and carbon dioxide from said resin; separating said carbon
dioxide from said water vapor; and delivering the carbon dioxide
for use in a secondary process.
10. The method of claim 9, wherein the secondary process is
selected from a group consisting of: machining coolant and
lubricant, grit blasting for smoothing and rust or paint removal,
cryogenic cleaning, quick freeze processes, R744 refrigerant, dry
cleaning solvent, perishable shipping container pre-cooling,
perishable shipping inert environment maintenance, beverage
carbonation, fire suppression, plant fertilization, horticulture,
agriculture, silvaculture, aquatic algae production, enhanced oil
recovery, water softening, Solvay process, propellant, pressurizing
gas, e.g. for aerosol cans, inflation gas, e.g. for life rafts,
supercritical CO.sub.2 extraction, semi conductor manufacturing,
organic solvent, perfume aromatics, decaffeinating coffee or tea,
supramics, pharmaceutical manufacturing, chemical production of
urea, methanol, inorganic carbonates, organic carbonates,
polyurethanes, paint pigments, foaming agents, carbon based fuels,
i.e. synthetic fuels, fumigation of farm products, neutralization
of alkaline waters or slurries or solid materials, or gas shield
for welding, or electronics manufacturing.
11. The method of claim 9, wherein said plurality of chambers are
connected via a plurality of valves that allow any of said
plurality of chambers to serve as said first chamber or said last
chamber.
12. The method as of claim 9, wherein said first chamber contains
resin that was most recently saturated or partially saturated with
carbon dioxide from said gas, and each successive chamber contains
resin which has been wetted and carbon dioxide collected from for a
greater period of time than the previous chamber, and so on, to
said last chamber.
13. A system for utilization of carbon dioxide that is
substantially carbon neutral, comprising a carbon dioxide capture
device that collects carbon dioxide from a fluid stream produced by
a process that utilizes carbon dioxide, wherein the carbon dioxide
capture device delivers the captured carbon dioxide for utilization
by the process.
14. The system of claim 13, wherein the process is selected from a
group of processes utilizing carbon dioxide consisting of: CO.sub.2
as a refrigerant, as a dry cleaning agent or other solvent, as a
fire suppression material, as an oxidation preventing shield-gas,
as an alternative to sand-blasting, synthetic fuel production,
plant fertilization, or as a freezing agent in food processing.
15. A method of creating tradable carbon credits which comprises
extracting CO.sub.2 from ambient air at a location adjacent or
remote from where the CO.sub.2 is generated, using sorbent,
selling, trading or transferring the resulting CO.sub.2 credits to
a third party, and using the extracted CO.sub.2 in a secondary
process.
16. A method for luring CO.sub.2 sensitive insects toward a
specific location where a moisture sensitive CO.sub.2 sorbent that
is partially or fully loaded with CO.sub.2 is exposed to moisture
usually in excess of that present in the ambient air at the
location.
17. The method of claim 16, wherein the sorbent is held in place by
an open basket that is protected with a roof and a floor against
accidental wetting by rain.
18. The method of claim 16, wherein the sorbent is a strong base
ion exchange resin.
19. The method of claim 16, wherein moisture is delivered from a
spray nozzle or as a puff of steam.
20. The method of claim 16, wherein the resin is woven into a
textile material that acts as a wick, can bring up water from a
separate reservoir that is filled either automatically or by hand
at a desired time.
21. The method of claim 16, wherein the sorbent is a resin that is
embedded into polymer matrix and wherein the polymer can contain a
contact active insecticide.
22. An apparatus for extracting a gaseous contaminant from a gas
stream using a sorbent employing a humidity swing and for
distilling a brine, comprising: a sorbent for capturing the
contaminant; a capture unit, wherein the sorbent is exposed to the
gas stream and becomes substantially saturated with the
contaminant; an evaporation unit, wherein a brine is evaporated
forming a concentrated brine and water vapor, and wherein the
sorbent is brought in contact with the water vapor causing the
sorbent to become substantially depleted of the contaminant
according to a humidity swing; and a condensation unit, wherein the
water vapor is separated from the contaminant.
23. The apparatus of claim 22, further comprising a heat exchanger
for conserving the heat retained by the sorbent from the
condensation unit and returning that heat to the evaporation
unit.
24. The apparatus of claim 22, wherein the contaminant is carbon
dioxide, and the gas stream is ambient air or an exhaust
system.
25. An apparatus for stabilizing the level of carbon dioxide in an
enclosed environment, comprising: a filter unit attached to said
enclosed environment, containing a sorbent material for carbon
dioxide capture; and a regenerating system for regenerating the
sorbent material at least in part.
26. The apparatus of claim 25, wherein the captured carbon dioxide
is delivered to the enclosed environment, to the surrounding
atmosphere, or to another desired location by the operation of a
plurality of louvers.
27. The apparatus of claim 25, wherein the sorbent material is an
ion exchange resin subject to a humidity swing.
28. The apparatus of claim 27, wherein the regenerating system
comprises one or more from a group consisting of: DI water, humid
air, condensate, and jetted steam.
29. A method for stabilizing the level of carbon dioxide in an
enclosed environment using the apparatus of claim 25, wherein the
level of carbon dioxide is maintained within predetermined
parameters,
30. The method of claim 29, further controlling the humidity in the
enclosed environment.
31. The method of claim 29, wherein the level of carbon dioxide is
optimized for the storage of produce.
32. The method of claim 29, wherein the level of carbon dioxide is
optimized for the storage of bananas.
33. A method for extracting carbon dioxide from a gas comprising
bringing a stream of the gas in contact with a sorbent, releasing
the carbon dioxide from the sorbent to create a carbon
dioxide-enriched gas mixture, and bringing the enriched gas mixture
in contact with an aqueous solution, wherein the aqueous solution
absorbs carbon dioxide from the gas mixture.
34. The method of claim 33, wherein the gas is brought in contact
with the aqueous solution by bubbling the enriched gas mixture
through the aqueous solution, or by flowing the gas over the
aqueous solution.
35. The method of claim 33, wherein the aqueous solution is an
alkaline brine, and wherein at least part of the carbon dioxide is
sequestered in the alkaline brine by forming carbonate ions,
thereby neutralizing the aqueous solution, and further comprising
the step of returning the aqueous solution to its origin.
36. The method of claim 33, wherein the enriched gas mixture is
brought in contact with the aqueous solution using a semi-permeable
membrane that allows the transfer of carbon dioxide from the gas
mixture to the aqueous solution; wherein the membrane is
hydrophobic and contains gas-filled pores; and wherein the membrane
allows the transmission of water vapor from aqueous solution to the
enriched gas mixture.
37. The method of claim 33, wherein water vapor is produced from
the aqueous solution to drive or partially drive the carbon dioxide
from the sorbent via a humidity swing, and wherein aqueous solution
and the sorbent are placed in close proximity so that heat consumed
in producing the water vapor is at least in part provided by
condensation of the water vapor in contact with the sorbent.
38. An apparatus, constructed to perform the method of claim 37,
wherein the sorbent is contained inside a tube whose walls have a
minimal heat resistance and that is open on both ends, and where
the outside of the tube is wetted by the aqueous solution so as to
maximize heat transfer between the inside and outside of the
tube.
39. The method of claim 33, wherein the aqueous solution is
contained in a sponge or foam.
40. The method of claim 33, including the step of utilizing the
extracted carbon dioxide to neutralizing waste alkaline brines.
41. The method of claim 40, including the step of utilizing the
extracted carbon dioxide for neutralizing alkaline brines that are
produced in the production of alkaline batteries, or that are
produced by injecting water into basaltic or other ultramafic or
other basic rock formations, or that are formed as mining waste
materials.
42. The method of claim 40, including the step of utilizing the
extracted carbon dioxide for neutralizing asbestos tailings.
43. A method for adding calcium bicarbonate to seawater without
changing the alkalinity of the water, comprising using a sorbent
that employs a humidity swing to extract carbon dioxide from the
air resulting in a gas mixture, precipitating carbonic acid from
the gas mixture to dissolve an amount of limestone, forming calcium
bicarbonate, and depositing the calcium bicarbonate in the seawater
with any remaining carbonic acid.
44. The method of claim 43, wherein the several steps are performed
upstream of a coral reef in order to increase the calcium and
carbonate ion product to enhance a growth rate of the coral
reef.
45. A method of stabilizing sorbent CO.sub.2 levels in storage
containers of fresh produce, comprising recovering excess CO.sub.2
from the storage containers using a sorbent for CO.sub.2.
46. A method for removing a gaseous contaminant from a gas stream,
comprising placing said gas stream in contact with a sorbent,
wherein the contaminant from said gas stream becomes loaded on said
sorbent; releasing the gas from said substrate by use of a humidity
swing; wherein the humidity swing is performed by evaporating a
brine to form concentrated brine and water vapor, and bringing the
water vapor in contact with the loaded sorbent; and condensing the
water vapor to separate the water vapor from the contaminant.
47. The method of claim 46, wherein the contaminant is carbon
dioxide, and the gas stream is an exhaust stream or is ambient
air.
48. The method of claim 46, wherein the sorbent is a solid ion
exchange material.
49. The method of claim 46, wherein a heat exchanger is used to
conserve the heat of condensation and returns the heat to be used
in the evaporation of the brine.
50. The method of claim 46, wherein the evaporation of the brine
occurs in an evacuated space.
51. The method of claim 46, wherein at least part of the condensed
water is captured and recycled.
52. The apparatus of claim 22, wherein the sorbent is a solid ion
exchange material.
53. The apparatus of claim 22, wherein the condensation unit is
cooled with water or seawater.
54. The apparatus of claim 22, wherein the evaporation unit is a
vacuum chamber.
55. The apparatus of claim 22, wherein the evaporation unit and the
condensation unit are part of the same chamber.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation application that claims
priority to U.S. application Ser. No. 13/737,818, filed Jan. 9,
2013; which is a Continuation application that claims priority to
U.S. application Ser. No. 12/389,213, filed Feb. 19, 2009; which
claims priority from U.S. provisional application Ser. No.
61/029,831, filed Feb. 19, 2008, Ser. No. 61/074,972 filed Jun. 23,
2008 and Ser. No. 61/079,776 filed Jul. 10, 2008.
FIELD OF THE INVENTION
[0002] The present invention relates to a method and apparatus for
the removal of selected gases from an environment and the disposal
of the selected gases in another environment.
BACKGROUND OF THE INVENTION
[0003] The present invention in one aspect relates to removal of
selected gases from the atmosphere. The invention has particular
utility in connection with the extraction of carbon dioxide
(CO.sub.2) from the atmosphere and subsequent sequestration of the
extracted CO.sub.2 or conversion of the extracted CO.sub.2 to
useful or benign products and will be described in connection with
such utilities, although other utilities are contemplated,
including the extraction, sequestration or conversion of other
gases from the atmosphere including NO.sub.x and SO.sub.2.
[0004] There is compelling evidence of a strong correlation between
the sharply increasing levels of atmospheric CO.sub.2 with a
commensurate increase in global surface temperatures. This effect
is commonly known as Global Warming. Of the various sources of the
CO.sub.2 emissions, there are a vast number of small, widely
distributed emitters that are impractical to mitigate at the
source. Additionally, large-scale emitters such as
hydrocarbon-fueled power plants are not fully protected from
exhausting CO.sub.2 into the atmosphere. Combined, these major
sources, as well as others, have lead to the creation of a sharply
increasing rate of atmospheric CO.sub.2 concentration. Until all
emitters are corrected at their source, other technologies are
required to capture the increasing, albeit relatively low,
background levels of atmospheric CO.sub.2. Efforts are underway to
augment existing emissions reducing technologies as well as the
development of new and novel techniques for the direct capture of
ambient CO.sub.2. These efforts require methodologies to manage the
resulting concentrated waste streams of CO.sub.2 in such a manner
as to prevent its reintroduction to the atmosphere.
[0005] The production of CO.sub.2 occurs in a variety of industrial
applications such as the generation of electricity from coal at
power plants and in the use of hydrocarbons that are typically the
main components of fuels that are combusted in combustion devices,
such as engines. Exhaust gas discharged from such combustion
devices contains CO.sub.2 gas, which at present is simply released
to the atmosphere. However, as greenhouse gas concerns mount,
CO.sub.2 emissions from all sources will have to be curtailed. For
mobile sources such as motor vehicles and airplanes the best option
is likely to be the collection of CO.sub.2 directly from the air
rather than from the mobile device in the motor vehicle or
airplane. The advantage of removing CO.sub.2 from air is that it
eliminates the need for storing CO.sub.2 on the mobile device.
[0006] Extracting carbon dioxide (CO.sub.2) from ambient air would
make it possible to use carbon-based fuels and deal with the
associated greenhouse gas emissions after the fact. Since CO.sub.2
is neither poisonous nor harmful in parts per million quantities,
but creates environmental problems simply by accumulating in the
atmosphere, it is possible to remove CO.sub.2 from air in order to
compensate for equally sized emissions elsewhere and at different
times.
BRIEF SUMMARY OF THE INVENTION
[0007] The present disclosure provides a system, i.e. a method and
apparatus for extracting a contaminant from a flow stream, such as
ambient air or an exhaust stack, and for delivering the extracted
contaminant for use in a secondary process. The present disclosure
is described primarily in regards to the removal and sequestration
of CO.sub.2, though the apparatus and method of the present
disclosure may be used with various other contaminants.
[0008] In accordance with one aspect of the present disclosure,
CO.sub.2 is extracted from air and the extracted CO.sub.2 is
delivered to a secondary process where the CO.sub.2 is transformed
into a useful or benign product. The CO.sub.2 is delivered in
whatever form is required for the secondary process, which may be
gaseous, solid, or liquid CO.sub.2. The secondary process may be
any manufacturing, food processing, or other industrial process
that uses CO.sub.2, such as, machining coolant and lubricant, grit
blasting, e.g. for smoothing and paint removal, cryogenic cleaning,
quick freeze processes, production and use of R744 refrigerant,
CO.sub.2 based dry cleaning solvents, perishable shipping container
pre-cooling, perishable shipping inert environment maintenance,
beverage carbonation, fire suppression, plant fertilization,
horticulture, agriculture, silvaculture, aquatic algae production,
enhanced oil recovery, water softening, Solvay process, propellant,
pressurizing gas, e.g. for aerosol cans, inflation gas, e.g. for
life rafts, supercritical CO.sub.2 extraction, semi conductor
manufacturing, organic solvent, perfume aromatics, decaffeinating
beverages, e.g. coffee and tea, supramics, pharmaceutical
manufacturing, chemical production such as for urea, methanol,
inorganic carbonates, organic carbonates, polyurethanes, paint
pigments, foaming agents, carbon based fuels, i.e. synthetic fuels,
fumigation, e.g. of grain elevators, neutralization of alkaline
water, gas shield, e.g. for welding, which are given as
exemplary.
[0009] A further aspect of the present disclosure provides a method
and apparatus for luring CO.sub.2 sensitive insects toward a
specific location where a moisture sensitive CO.sub.2 sorbent that
is partially or fully loaded with CO.sub.2 is exposed to moisture
usually in excess of that present in the ambient air at the
location. The sorbent may be held in place by an open basket that
is protected with a roof and a floor against accidental wetting by
rain.
[0010] Another aspect of the present disclosure is directed to the
control of the concentration of specific gases in a closed
environment. While the method and apparatus of this aspect of the
present disclosure will be described with specific reference to the
control of carbon dioxide in the storage, for example, of bananas,
but other fruits and vegetables are also contemplated by this
disclosure. The present invention provides a atmosphere-controlled
environment for storing produce, wherein other parameters as well
as carbon dioxide such as humidity may also be controlled, and a
plurality of filters attached to the temperature controlled
environment.
[0011] Yet another aspect of the present disclosure provides a
system, i.e. a method and apparatus for extracting carbon dioxide
(CO.sub.2) from ambient air or an exhaust stack and for delivery,
sequestration or conversion of the extracted CO.sub.2 into useful
or benign products.
[0012] The extraction of the contaminant from a gas stream in any
of the aspects of the present disclosure discussed above may be
accomplished by using one of a number of methods such as disclosed
in the several patent applications listed in Appendix A, the
contents of which are incorporated herein by reference, as well as
other extraction processes described in the literature and patent
art, including processes which capture CO.sub.2 at the stack.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Further features and advantages of the present invention
will be seen from the following detailed description, taken in
conjunction with the accompanying drawings, wherein
[0014] FIG. 1 is a schematic showing a system for capturing
CO.sub.2 in accordance with the present invention wherein CO.sub.2
is delivered to a secondary process;
[0015] FIG. 2A is a schematic showing an ion exchange process for
capturing CO.sub.2 in accordance with one aspect of the present
disclosure wherein multiple chambers are used in succession;
[0016] FIG. 2B is a schematic showing an ion exchange process for
capturing CO.sub.2 where valves are used to control flow between
chambers in accordance with the present disclosure;
[0017] FIG. 3 is a schematic showing an ion exchange process for
capturing CO.sub.2 employing activated carbon in accordance with
one aspect of the present disclosure;
[0018] FIG. 4 is a schematic of an apparatus of the present
invention having an electrodialysis cell according to one
embodiment of the present disclosure;
[0019] FIG. 5 is a schematic showing a system for capturing
CO.sub.2 in accordance with the present disclosure wherein the
CO.sub.2 capture device works in tandem with an industrial process
to create an essentially carbon neutral system;
[0020] FIG. 6 is a schematic of a method and apparatus for luring
CO2-sensitive insects to a desired location according to one aspect
of the present disclosure;
[0021] FIG. 7 is a schematic of a method and apparatus for luring
CO2-sensitive insects to a desired location according to one aspect
of the present disclosure.
DETAILED DESCRIPTION
[0022] Various methods and apparatus have been developed for
removing CO.sub.2 from air. For example, we have recently disclosed
methods for efficiently extracting carbon dioxide (CO.sub.2) from
ambient air using sorbents that either physically or chemically
bind and remove CO.sub.2 from the air. A class of practical
CO.sub.2 capture sorbents include strongly alkaline hydroxide
solutions such as, for example, sodium or potassium hydroxide, or a
carbonate solution such as, for example, sodium or potassium
carbonate brine. See for example published PCT Application
PCT/US05/29979 and PCT/US06/029238. See also published PCT
Application PCT/US07/802,229 which describes the use of solid
sorbents such as ion exchange resins for removing CO.sub.2 from the
air.
[0023] In broad concept, the present invention in one aspect
extracts carbon dioxide from ambient air using a conventional
CO.sub.2 extraction method or one of the improved CO.sub.2
extraction methods disclosed in our aforesaid PCT applications, or
disclosed herein, and releases at least a portion of the extracted
CO.sub.2 to a secondary process employing CO.sub.2. The CO.sub.2
also may be extracted from an exhaust at the exhaust stack.
[0024] In our co-pending U.S. application Ser. No. 11/866,326,
assigned to a common assignee and incorporated by reference herein,
there are provided methods and apparati for extracting carbon
dioxide (CO.sub.2) from ambient air and for delivering that
extracted CO.sub.2 to controlled environments. Specifically, the
aforementioned applications disclose the delivery of CO.sub.2
collected from ambient air or from exhaust gases for use in
greenhouses or in algae cultures. The CO.sub.2 is extracted from
the gas stream by an ion exchange material that when exposed to dry
air absorbs CO.sub.2 that it will release at a higher partial
pressure when exposed to moisture. In this process we can achieve
concentration enhancements by factors of from 1 to 100.
[0025] In a first exemplary embodiment shown in FIG. 1, the present
invention provides a system for removing CO.sub.2 from a fluid
stream in a capture apparatus, comprising passing the fluid stream
in contact with a primary sorbent to absorb CO.sub.2 from the fluid
stream. The fluid stream may be ambient air, a flue stream, or any
other fluid stream from which the sorbent is capable of withdrawing
CO.sub.2. The CO.sub.2 is then released by the primary sorbent and
delivered to a secondary process.
[0026] The secondary process preferably is connected directly to
the CO.sub.2 capture apparatus to minimize transportation costs and
potential losses associated therewith. Depending on the intended
secondary process, the CO.sub.2 may be transformed into a solid or
liquid state. The CO.sub.2 may further be conditioned to a
specified pressure and/or temperature.
[0027] The secondary process may be any manufacturing, food
processing, or other industrial process that uses CO.sub.2, such as
for example, machining coolant and lubricant, grit blasting, e.g.
for smoothing and paint removal, cryogenic cleaning, quick freeze
processes, R744 refrigerant, dry cleaning solvent, perishable
shipping container pre-cooling, perishable shipping inert
environment maintenance, beverage carbonation, fire suppression,
plant fertilization, horticulture, agriculture, silvaculture,
aquatic algae production, enhanced oil recovery, water softening,
Solvay process, propellant, pressurizing gas, e.g. for aerosol
cans, inflation gas, e.g. for life rafts, supercritical CO.sub.2
extraction, semi conductor manufacturing, organic solvent, perfume
aromatics, decaffeinating beverages, e.g. coffee and tea,
supramics, pharmaceutical manufacturing, chemical production such
as for urea, methanol, inorganic carbonates, organic carbonates,
polyurethanes, paint pigments, foaming agents, carbon based fuels,
i.e. synthetic fuels, fumigation, e.g. of grain elevators,
neutralization of alkaline water, gas shield, e.g. for welding,
Many other processes utilizing CO.sub.2 are also possible and are
deemed to be within the scope of this disclosure.
[0028] Our aforementioned commonly owned applications disclose
several potential primary sorbents that may be used to capture and
remove CO.sub.2 from the air. In one approach to CO.sub.2, capture,
the sorbent is a strong base ion exchange resin that has a strong
humidity function, that is to say, an ion exchange resin having the
ability to take up CO.sub.2 as humidity is decreased, and give up
CO.sub.2 as humidity is increased. Such resins may be regenerated
by contact with water, humid air, or pulses of steam. In this
approach the CO.sub.2 is returned to a gaseous phase in a more
concentrated form, and no liquid media are brought in contact with
the collector material.
[0029] Other primary sorbents may be regenerated by a secondary
sorbent such as weak liquid amine. This amine must be capable of
pulling the CO.sub.2 content of gas mixture down so that the
CO.sub.2 partial pressure drops to about e.g., 20 to 30 mbar. Thus
it can be far weaker sorbent than the primary sorbent and this
allows the use of very weak amines.
[0030] Still other sorbent materials may be regenerated by the
application of heat (utilizing a thermal swing), or vacuum
pressure.
[0031] In another example, CO.sub.2 is captured and removed from
air on a solid phase ion-exchange resin which is placed in a
plurality of chambers connected in series. See FIG. 2A. The resins
in the different chambers have been exposed for different length of
time to the outgassing process. Resins may move from chamber to
chamber, or more likely as shown in FIG. 2B, the valving is changed
to take a chamber from the purged end of the chain, remove its
charge and fill it with a resin which is now put on the unpurged
end of the chain. The gas in each chamber is composed of water
vapor, CO.sub.2 and possibly an inert sweep gas. The sum of the
three partial pressures monotonically declines from the upstream
end of the system to the downstream end of the system. The sweep
gas pressure can be reduced by increasing the flow speed, but the
water vapor pressure is more or less in equilibrium with the liquid
water at this point. The CO.sub.2 pressure should increase in the
direction of the sweep. If the water vapor is a large part of the
total pressure, the water vapor pressure gradient controls the flow
and it would be established by a temperature drop from one chamber
to the next, while the CO.sub.2 pressure will rise from one chamber
to the next, as each chamber is adding some CO.sub.2 to the flow.
The contributions of each chamber will be limited by the rate at
which the material can release CO.sub.2 and the equilibrium
pressure that particular resin can reach.
[0032] The following conceptually describes a CO.sub.2 washing
system that is based on immersing the resin into liquid water and
moving the water over the resin into a separate chamber where the
CO.sub.2 is allowed to be released from the water.
[0033] A simple implementation is a set of chamber organized (at
least logically into a circle). All but one chamber are filled with
water. One chamber (n) is empty and filled with air. Initially
chamber n is filled with air, and chamber n+1 is filled with water.
Now water is pumped against a minimal pressure drop from chamber k
to k+1. This will work for all values of k, except that k=n-1, n,
n+1 are special cases which need further consideration. The water
in chamber n-1 flows into chamber n, thereby pushing the air inside
this chamber out. It is either released to the outside or channeled
into chamber n+1 whose water content is moving into chamber n+1.
The water pouring into chamber n will inundate the resin that has
been replaced into this chamber. The water in chamber n+1 flows
into chamber n+2, but rather than obtaining water from chamber n,
it pulls in air, which may be the air that resided in chamber n, or
fresh air taken from the outside.
[0034] At this point we renumber all chambers by replacing n with
n-1. Thus it is again chamber n that is filled with air. We now
open chamber n, and remove the regenerated resin and replace it
with fully loaded resin. Before we load up chamber n, we pump the
water from station n-1 to a degassing station and from there to
station n+1. This water flow bypasses the currently open chamber
n.
[0035] This procedure could be used with pure water, in which the
process is a simple degassing, but it could also be performed with
a carbonate solution which is turned into a bicarbonate and where
the CO.sub.2 is removed by other means. CO.sub.2 removal could be
based on an evacuation (which could be achieved by operating an
inverted siphon), or based on electrodialysis, or involve a
secondary sorbent that is far more compact and thus allows for an
easier regeneration option. It also could involve precipitation of
bicarbonate from the solution in a thermal swing or a thermal swing
for CO.sub.2 release from the mixture. The basic layout is
independent of these ideas.
[0036] A variation of this idea has all chambers evacuated with the
exception of chamber n-1 which is filled with water, n which is
open to the air, and n+1 which is again filled with water. The
nominally evacuated chambers are filled with a mixture of water
vapor and CO.sub.2. In this case, we pump water from chamber n-1
into n, displacing the air to the outside and immersing the resin
in water. The pump does not need to do much work, because at the
same time the water in chamber n+1 is sucked into chamber n+2,
while chamber n+1 fills itself with air. At the end of this process
chamber n+1 is filled with air and open to the outside. Chamber n
is filled with water and at vacuum pressure. Chamber n+2 is filled
with water and at vacuum pressure, and all other chambers are still
under vacuum conditions. No net work was done, but all chambers
moved by one. We can now renumber all chambers, and repeat the
cycle.
[0037] In this case we use the water to stimulate the gas release
and the freshly wetted resin in the last chamber is now topping off
the CO.sub.2 which is pumped out of this chamber, letting gas flow
from all other chambers into this one. The CO.sub.2 content of the
water is likely to be high, however, it remains more or less
constant over time as we do not extract this CO.sub.2, so after
some initial transients, this CO.sub.2 reservoir will remain
constant and not remove CO.sub.2 from the resin (we ignore here
some small losses to the outside air which are not completely
avoidable) check valves can be installed to prevent backward flow.
As a result we have a water driven implementation of the CO.sub.2
release which his significantly simpler than a water vapor driven
system.
[0038] Optionally, some of the water vapor may be recovered from
the system during the compression stage. This will provide
sufficient heat that the system can operate at slightly elevated
temperatures. Indeed it is possible to use the last step of pumping
out of the gas to severely cool the resin and remove all excess
water.
[0039] Yet other possibilities exist. For example, it is possible
to create a buffer storage for the water which makes it possible to
slowly withdraw water from chamber n-1 and in a second step fill
chamber n very rapidly so as to minimize the amount of time the
water is in contact with air and thus can exchange gas with the
outside air. The buffer itself must be able to change volume. It
takes on an additional volume as it takes on the fluid from chamber
n-1. It then contracts again as it pushes the same volume into
chamber n. Again mechanical work is related to friction losses,
inertial losses, and losses to slight pressure mismatches between
the various chambers. This can be adjusted for with careful thermal
management.
[0040] In yet another example CO.sub.2 is captured and removed from
air by employing hydrophobic activated carbon materials with strong
base ion exchange resins. See FIG. 3. This latter process is based
on observation that activated carbon has been observed to absorb
CO.sub.2 when wet, and release the absorbed CO.sub.2 as it dries.
This is the opposite behavior from ion exchange resins.
Accordingly, this makes it possible to couple solid phase ion
exchange resin extractors and activated carbon extractors in
sequence. Starting with dry activated carbon and moistened resin
materials air is passed through the system. As the air dries the
resin, it transports the water vapor to the carbon. The resin picks
up CO.sub.2 as it dries, and the activated carbon picks up CO.sub.2
as it accepts moisture. Once the resin is dry, the system is
reversed, and fresh air is flowed through the activated carbon, and
releases moisture back to the ion exchange resins. As the carbon
dries it gives off CO.sub.2, raising the CO.sub.2 partial pressure
where it can be concentrated and removed. A feature and advantage
of coupling ion exchange material and activated carbon in this
manner is that water is preserved, and is a simple matter of
valving to reverse air flow.
[0041] Alternatively, zeolite materials may be used in place of
activated carbon. By stringing several air capture devices
together, the ambient CO.sub.2 removed may be concentrated before
passing to a secondary process.
[0042] The same ion exchange resins may be used to remove excess
CO.sub.2 build-up from closed containers such as storage containers
for fresh fruit or vegetables, e.g., bananas, in order to maintain
a maximum level of CO.sub.2 in the container and avoid excessive
ripening or spoilage, as will be described in greater detail
below.
[0043] In another aspect of the present invention shown in FIG. 4,
CO.sub.2 is captured using ion exchange materials and concentrated
using an electrodialysis (ED) cell. The overall process is as
follows: The ion exchange resin is washed using a basic solution,
such as sodium carbonate (Na.sub.2CO.sub.3), preferably having a pH
of 11-12. The resulting effluent, which in the example of a sodium
carbonate wash will be primarily sodium bicarbonate (NaHCO.sub.3),
will preferably have a pH of 9-10. The effluent is then supplied to
the acid side of an ED cell, where the reaction is controlled
through bipolar and cationic membranes. After an initial run, the
acidic side of the cell stabilizes at a near neutral pH, at which
point CO.sub.2 evolves and is captured. Osmotic pressure drives
water towards the base side of the cell. The basic solution is
maintained near a pH of 12 and may also be used to replenish the
wash fluid.
[0044] In another exemplary embodiment shown in FIG. 5, the present
invention provides a system that is substantially carbon neutral,
wherein an air capture device, such as those described herein,
collects CO.sub.2 that is released by an industrial process
employing CO.sub.2 as described above. For example, such processes
include the use of CO.sub.2 as a refrigerant, as a dry cleaning
agent or other solvent, as a fire suppression material, as an
oxidation preventing shield-gas in welding or electronics
manufacture, as an alternative to sandblasting, e.g., for
smoothing, or paint or rust removal, as a freezing agent in food
processing, or any other process where CO.sub.2 is utilized and is
later released to the atmosphere. The system effectively creates a
loop that is substantially carbon neutral. The air capture device
may, for example, be connected the HVAC system of a building where
CO.sub.2 is released by processes therein. With the present
invention, CO.sub.2 is captured, concentrated and recycled for
reuse on site.
[0045] The invention also may be used to generate carbon credits.
Thus, a manufacturer may extract CO.sub.2, and obtain a carbon
credit which may be traded or sold, and then use the extracted
CO.sub.2 in a secondary process, eliminating the cost of purchasing
or generating CO.sub.2 for the secondary process.
[0046] Another aspect of the present disclosure provides an
apparatus and method for using captured CO.sub.2 to attract
CO.sub.2 sensitive insects, such as mosquitoes. It is known that
certain insect pests like mosquitoes are attracted to sources of
CO.sub.2, which for them is a way to find a potential victim. In
recent years lures have been developed for mosquitoes that release
CO.sub.2 in the environment in order to attract mosquitoes and
potentially other insects. A drawback of most of these devices is
that they require gas cartridges of CO.sub.2 or natural gas,
propane or butane to produce CO.sub.2. In related applications it
has been shown how certain ion exchange materials can be used to
absorb CO.sub.2 when they are in a dry state and release it again
when they get wet. Here an application of such a material is
described wherein the controlled CO.sub.2 release is used to
attract mosquitoes to a device at certain times while at other
times the device recharges its CO.sub.2 stores.
[0047] Referring to FIG. 6, his aspect of the present disclosure
describes a method of luring CO.sub.2 attracted insects by using a
CO.sub.2 capture resin that when dry will collect CO.sub.2 from the
air and release it again when exposed to moisture. A number of such
materials have been described in previous disclosures. This
disclosure describes how these resin materials can be used to lure
mosquitoes to the device at certain times.
[0048] It is possible to expose an amount of resin to air so as to
load it with CO.sub.2. When the device is activated, e.g. in the
evening the resin is exposed to humid air, or is directly wetted
for example by a small water spray. As a result the resin will
begin releasing CO.sub.2 therefore creating an environment that
will attract mosquitoes. One implementation, for example, would be
a small container filled with polymer strands of the ion exchange
resins and similar materials that can be used to absorb CO.sub.2.
The purpose of the CO.sub.2 release is to attract certain insects,
like mosquitoes that are attracted by CO.sub.2.
[0049] The device exposes resin to the air, and containing the
resin in a way that is protected from water and rain. During times
the device is inactive, it is dry and the resin will collect
CO.sub.2. The device includes a means of applying moisture to the
resin material Moisture application could be achieved by spraying
water onto the resin surface, by wicking water into a woven wick
that contains the resin material, or by any other means known in
the art.
[0050] The device acts as a lure to attract mosquitoes away from
people. In this case the device can be completely open, because no
part needs to be kept away from people. In another implementation
the device includes means of killing the pest once it enters the
device. This includes but is not limited to electric discharges, or
by contact insecticides embedded into the resin matrix.
[0051] It is possible to combine the CO.sub.2 lure with other means
of attracting insects, including insects that do not respond to the
presence of CO.sub.2. These means include, but are not limited to
light and heat sources, sounds, odors or pheromones. Devices of
this nature can be designed for indoor and outdoor use. Indoor use
in malaria regions may help suppress the incidence of mosquitoes
and hence malaria.
[0052] Another aspect of the present disclosure relates to the
capture and release of gases generated by the ripening and
preservation of fruits and vegetables. Many produce items, i.e.,
fruits and vegetables, are often stored in a temperature-controlled
environment in order to control the ripening process. Methods for
the packaging and shipping of such fruits and vegetables have been
developed to maximize the amount of time that the produce may be
stored. Many methods for storing and ventilating produce are known
that provide various types of bags and containers, including gas
permeable membranes, that allow some control of the exposure of the
produce to gases such as oxygen, ethylene, and carbon dioxide.
However, these methods do not provide optimal storage conditions
and long-term storage options are still desired.
[0053] U.S. Patent Publication No. 2008/0008793, incorporated by
reference herein, discloses a method for storing bananas in a
controlled environment where oxygen and carbon dioxide levels are
optimized in addition to the temperature. Longer periods of storage
may be achieved in this environment and improved flavor
characteristics may be achieved. The reference fails, however, to
discuss how such levels would be reached and maintained.
[0054] This aspect of the present disclosure provides a method for
to stabilizing the CO.sub.2 in a room at any level between 5 ppm
and 100,000 ppm. The invention also serves to achieve a low
absolute humidity (usually below 25 ppt of water vapor, preferably
below 15 ppt, with improved performance as the absolute humidity
drops even lower).
[0055] Referring to FIG. 7, the method comprises circulating air
through a filter box that follows one of the methods for CO.sub.2
absorption describes in one of our aforesaid previous applications.
For example, the filter may employ an ion exchange resin that is
subject to a humidity swing to absorb CO.sub.2 at the partial
pressure representing the desired CO.sub.2 level. The apparatus may
include a plurality of such filters operating, wherein each filter
will run until the CO.sub.2 uptake rate has slowed down to a
predetermined level at which we consider the resin to be
essentially fully loaded. This will probably by less than the
maximum loading for the resin that can be physically be achieved,
but the predetermined level may be optimized for performance at
some lower level to improve the collective uptake rate. The uptake
rate of the resin will depend primarily on absolute humidity and to
some extent on temperature, and can approach one CO.sub.2 per
positive elementary fixed charge in the resin.
[0056] Once the resin is loaded the air intake is closed or the
resin filter may be moved into a separate chamber. A humidity swing
regeneration step follows. Regeneration is accomplished by a change
in temperature and absolute humidity, or by wetting the resin,
e.g., as described, for example, in U.S. Pat. No. 4,711,645; U.S.
Pat. No. 5,318,758; U.S. Pat. No. 5,914,455; U.S. Pat. No.
5,980,611; U.S. Pat. No. 6,117,404; and co-pending U.S. application
Ser. No. 11/683,824, and PCT Application Serial No. PCT/US08/82505.
Wetting can be accomplished by either dipping the resin into DI or
condensation water; by spraying or flowing such water over the
resin, (such condensation water may be available from the
refrigeration unit operating the storage facility, and may be
augmented by condensation water recovered from our unit); by
generating steam in a blast of warm air that results in water
condensation on the resin material; or by exposing the resin to
warm moist air (such warm air may be available from the hot side of
the refrigeration unit, it may already be moist or need additional
moisture.) If the moisture is added as humidity or by generating
steam, it is not necessary to use DI or condensation water.
[0057] The moist air loaded with CO.sub.2 is then purged from the
unit. Heat and water may be recovered in a heat exchange unit that
reduces heating demand and water consumption.
[0058] The present disclosure as discussed above may be used to
cover a range of applications from extremely low levels of CO.sub.2
to extremely high levels of CO.sub.2. It is in principle possible
to remove CO.sub.2 from a gas stream that contains CO.sub.2 far in
excess of the levels discussed above. Levels around 1 to 10 volume
percent could easily be accommodated, and operating above about 10
volume percent CO.sub.2 is also possible. It is advantageous for
this design to operate at temperatures below about 15.degree. C.,
because the loading and unloading characteristics of the resin
improve under these conditions.
[0059] Alternative options at elevated levels of CO.sub.2 include
the use of activated carbon, the use of zeolites, the use of weak
based amine, or other physical sorbents such as actuated alumina
for CO.sub.2 capture instead of ion exchange resin.
[0060] In broad aspect the present invention provides a method and
apparatus for the extraction of a contaminant from a gas stream.
The present invention will be described in reference to a method
and apparatus for capturing CO.sub.2 from ambient air; however, the
invention is also applicable to handling exhaust air or other gas
streams and may be used to capture hydrogen sulfide, ammonia, or
other common contaminants from such gas streams.
[0061] In co-pending PCT International Patent Application Serial
No. PCT/US07/84880; U.S. Provisional Patent Application Ser. No.
60/985,586, assigned to a common assignee and incorporated by
reference herein, we discuss a CO.sub.2 capture process that
utilizes a humidity swing to regenerate a sorbent, releasing a
mixture of CO.sub.2 and water vapor. The water vapor may be removed
from the mixture by compression or cooling, either of which will
cause the water vapor to condense and precipitate out of the
mixture.
[0062] To perform the humidity swing, it often is useful to expose
the sorbent to low pressure water vapor. In order to achieve the
required minimum water vapor pressure, it is may be necessary to
operate above ambient temperatures as the maximum water vapor
pressure is significantly dependent on temperature. To that end,
the aforementioned co-pending applications discuss how to transfer
heat to loaded sorbents that need to be inserted into an
environment that is at a higher temperature.
[0063] In regenerating the sorbent it is necessary to dry the resin
material. This opens an opportunity to combine such system with a
vacuum distillation system, and use the heat of evaporation that is
released when the material is drying to remove heat from the
condenser inside the vacuum distillation system. Whereas the
recovery of the CO.sub.2 in most applications requires entering the
resin material into a vacuum chamber, the present invention also
may be used to drive a complimentary distillation process.
[0064] As explained in the aforementioned co-pending applications,
the CO.sub.2 sorbent is often an anionic exchange resin, but here
we intend to consider all humidity-sensitive CO.sub.2 sorbents that
can absorb carbon dioxide from the air when they are dry and
release carbon dioxide when they have been exposed to humidity in
the form of liquid water and/or partial pressures of water vapor
which exceed those at ambient conditions. We will generally refer
to such materials as water-sensitive CO.sub.2 sorbents.
[0065] Vacuum distillation is a standard method of creating fresh
water from a brine, such as seawater, brackish water or other salt
rich brines pumped from underground. For purposes of this
disclosure, brine is also used to refer to contaminated water that
is otherwise unsuitable as fresh water, such as for example, waters
contaminated with biological waste materials. Thus, the term
"brine" encompasses all waters contaminated with materials from
which water can be separated by vacuum distillation.
[0066] Vacuum distillation begins with a chamber that has been at
least partially evacuated. Brine is introduced into the chamber and
is separated into two components: concentrated brine fresh water
product. There are many ways to supply a fluid into a vacuum
chamber that are known to practitioners of the state of the art. By
adding and subtracting from the vacuum chamber equal volumes of
incompressible fluid it is possible to design a continuous flow
system that requires only minimum amount of mechanical work.
[0067] The apparatus comprises a vacuum chamber that is divided
into at least two parts; an evaporator unit and a condenser unit.
As brine is introduced into the evaporator unit, it is allowed to
evaporate. In this manner the water vapor becomes separated from
the contaminants in the brine. The water vapor is then passed to a
condenser unit, where it is allowed to condense. It is necessary to
remove heat of condensation to keep from impeding further
condensation in the condenser unit. This heat may be passed to the
evaporator unit, enabling the evaporation to occur, by counterflow
or some other method.
[0068] The evaporator unit, which is initially evacuated, fills
with water vapor. The equilibrium partial pressure over the brine
in the evaporator unit is a function of the temperature and of the
salt content of the brine. The equilibrium partial pressure over
the condensate in the condenser unit is a function of the
temperature. At equal temperature, the equilibrium partial pressure
over the condensate is slightly higher than over the brine. Thus,
in a system with constant temperature the brine would gradually
dilute itself with water extracted from the condensate. The system
left to itself would operate in reverse, just as saltwater will
become more dilute when it is separated from fresh water with a
semi-permeable osmotic membrane.
[0069] One way to condense the water vapor in the condenser unit is
to raise the pressure, wherein the water vapor will condense at
ambient temperatures. This may be accomplished using a compressor
to drive up the pressure. The heat of condensation will cause the
temperature to rise in the condenser unit, wherein the heat
deposited by the condensation can then be transferred to the
evaporator unit. The compression acts in effect as a heat pump
which transfers heat from the brine to the condensate, and a return
heat flow balances out the total heat fluxes inside the system.
[0070] Where compression is used to condense the water out of the
resulting gas mixture, the heat produced by that process can be
transferred to the sorbent to raise its temperature as required.
Alternatively, the heat required to drive the sorbent to the
requisite temperature can also be derived from the condensation of
water that has been allowed to evaporate at ambient conditions.
[0071] Another approach is to maintain by some other system a
temperature gradient between the evaporator unit and the condenser
unit, which is enough to cause a gradient in the equilibrium
partial pressure that causes vapor to flow from the evaporator unit
to the condenser unit. In order to maintain such a temperature
differential, it is necessary to provide the heat of evaporation on
the evaporator unit, and remove the heat of condensation on the
condenser unit of the chamber. The required temperature differences
are small; a few degrees between the evaporator and the condensate
are sufficient. Operational temperatures can be low and could be
well within the range of ambient temperatures, particularly in
warmer climates.
[0072] One way of establishing the temperature gradient is to
generate heat and transfer it to the evaporator. Another way of
establishing the temperature gradient is to actively remove heat on
the condenser unit. This requires a heat exchange system that
removes heat from the condensate. In such an operation of the
device, the temperature of the brine is higher than that of the
condenser unit the heat is passed through and cannot be recovered
within the system. In principle it is possible to couple one or
more additional heat pumps to the system, which pumps the heat
removed at the condenser unit and returns it to the evaporation
side.
[0073] In combination with the CO.sub.2 capture system described
above, the water vapor is evaporated from the brine and is partly
absorbed onto the resin. This will release a substantial portion of
the CO.sub.2 or other targeted contaminant from the sorbent. When
this step is performed in a vacuum chamber, the atmosphere of the
chamber will be filled primarily with water vapor and CO.sub.2. The
vacuum chamber will also aid in the evaporation of the water vapor
in the brine. The concentrated brine is then removed and the water
is then condensed out of the CO.sub.2. Thus, the present invention
produces a distilled water stream as well as concentrated
CO.sub.2.
[0074] Providing heat to the drying resin is advantageous and one
can therefore integrate a heat exchange system operating between
the drying resin collector and the condenser inside the vacuum
system. In a typical implementation the evaporation of the water
from the resin would not produce quite enough water to make up the
water losses from the system; therefore it would have to be
augmented by additional brine evaporation.
[0075] Another aspect of the present disclosure provides a
different process whereby ambient environmental temperatures are
used to maintain a constant temperature at the condenser unit, i.e.
by flowing ambient air, or ambient water through the heat exchanger
on the brine evaporation side, and we use additional brine, e.g.
seawater, to operate an evaporative cooler that creates the
temperature drop necessary to force the condensation of clean water
inside the vacuum chamber. The amount of seawater that needs to be
evaporated on the outside of the chamber to maintain a low
temperature is approximately equal to the amount of brine that is
converted in the vacuum distiller.
[0076] The system disclosed herein comprises a vacuum chamber with
means of introducing and removing a brine, with means for removal
of clean water condensate, with internal surfaces on which the
brine is allowed to evaporate, and surfaces of a lower temperature
where the water vapor is allowed to condense. The surfaces on which
the brine is evaporating are in close contact with a heat exchanger
that provides the necessary heat to maintain evaporation. It is
advantageous to use free heat, i.e., heat from the ambient
environment, which may have been augmented by heat, e.g. from
sunshine, or, e.g. waste heat. The surfaces on which water vapor is
allowed to condense are in close contact with a heat exchanger that
uses additional brine to provide evaporative cooling required to
force the condensation.
[0077] In the above embodiment, brine is consumed both inside and
outside the chamber. The maximum acceptable concentration of the
discharge brine will limit the amount of evaporation that is
acceptable. The rate of consumption in both cases is similar. The
two waste streams can be combined and mixed for return to the ocean
or brine reservoir. The returned concentrated brine is slightly
cooler than ambient temperatures.
[0078] Where ocean water or any water from a large body of water is
used, it is not unusual for the input water is already cooler than
ambient temperatures. In this case, it is possible to take
advantage of the additional cooling power derived from the cool
water that is in the system.
[0079] In addition, one might use a CO.sub.2 membrane that
separates CO.sub.2 from nitrogen and oxygen. One option would be to
use a carbonic anhydrase based membrane separation technology. Of
particular utility are membranes with similar properties to the ion
exchange resin discussed more fully in our other applications; (see
Appendix A). The thin resin membrane would transfer CO.sub.2
according to a pressure gradient in CO.sub.2 and against a pressure
gradient in water vapor. The two combined create a net flow of
CO.sub.2 across the membrane and thus by keeping the outside of the
membrane wet or in high humidity one would create two chemical
potentials that will drive CO.sub.2 across the membrane.
[0080] Finally, there is a great synergy with the climate control
of the current chamber. The CO.sub.2 management is preferably
integrated with de-humidification, or humidification of the air as
the case may be, and it may also be integrated with the temperature
control and AC handling of the air. The CO.sub.2 stabilization
unit, shares the air handling and blowing equipment with the other
tasks, and it may be built into the same set of ducts. It can take
advantage of heat and condensation water produced in the
refrigeration unit.
[0081] The present disclosure in another aspect provides an
additional use for extracted CO.sub.2. According to the present
invention, the extracted CO.sub.2 is employed to neutralize
carbonic acid. The present invention takes advantage of the fact
that in sequestration, if one can drive the partial pressure of
CO.sub.2 up by about a factor of about 100, the concentrated
CO.sub.2 may then be injected into alkaline brines, to neutralize
the brine.
[0082] The resins disclosed in our previous U.S. Provisional Patent
Appln. 60/985,586 and PCT International Patent Appln. Serial No.
PCT/US08/60672, assigned to a common assignee, make it possible to
capture CO.sub.2 from the air and drive it off the sorbent with no
more than excess water vapor. It also is possible to wet the resin
directly with liquid water and form a carbonate, and transfer the
carbonate in a second step through a membrane between the two
fluids. However, in most cases, it is preferable to create a
concentrated CO.sub.2 gas that then can be transferred directly
into a more alkaline brine. Here again we can make direct contact
between the gas and the brine, or keep them separated by a
hydrophobic, porous membrane.
[0083] There are many applications where one has access to alkaline
underground brines that can be used to drive a humidity swing with
ionic exchange sorbents, even if their ion content make them
unsuitable for direct contact with the resin. The present invention
takes advantage of the humidity swing and transfers the CO.sub.2
through the gas phase. Alternatively, hydrophobic membranes may be
used to create a gas phase interface between two liquids, or
between a liquid and a gas. If the brine covers one side of the
membrane it is possible to pull CO.sub.2 gas through the membrane
without bringing contaminant ions in contact with the sorbent
resin.
[0084] A particular application of this technology can be realized
where some other industrial process has created a highly alkaline
waste stream that needs to be neutralized before disposal. In that
case, we can introduce carbonic acid, which will either cause the
precipitation of insoluble carbonates, or produce soluble but
neutral carbonate salts. Similar processes are disclosed in (PCT)
Publication Number WO/2005/047183. As an example, consider waste
streams from bauxite processing, e.g. in the Bayer process, which
produces "red mud" at pH 13. According to the PCT application cited
above, between 1990 and 2003 six to seven million tons of red mud
have been produced. Another example mentioned in the reference is
the reprocessing or disposal of potassium hydroxide solutions from
alkaline batteries. The process of the present invention would
create potassium carbonate or bicarbonate producing materials that
are indeed quite harmless.
[0085] In one aspect of the neutralization process according to the
present disclosure, we propose to use an alkaline brine which is
preferably in a temperature range between 40 and 60.degree. C., and
use the water vapor to recover CO.sub.2 from our resins. We then
wash the CO.sub.2 out of the gas mixture with the help of the
alkaline brine. The heated alkaline brine will provide a high level
of moisture which induces the resin to give off CO.sub.2 while it
at the same time prevents the CO.sub.2 level from rising
substantially. If operated in a vacuum the process should not be
transport limited. In the presence of atmospheric pressures,
however, the process could be transport limited.
[0086] One possible approach is to have the liquor be soaked up in
open cell foams such as AQUAFOAM.RTM. floral retention foam as
described in our PCT Published Application No. WO2006/084008.
Another is to have it trickle through a packed bed that is
installed parallel to the resin recovery unit and cycles gas from
the recovery unit through it. Another option is to contain the
resins in a tube whose outside is covered with a material that
soaks up the brine. In such a design heat transfer between inside
and outside the tube is optimized.
[0087] The resin, which has been saturated with CO.sub.2 in ambient
air, is brought into a chamber connected to a second chamber
containing wetted surfaces over which the brine flows. The brine
will establish a high level of humidity and the resulting high
humidity air is blown over the sorbent material. In one aspect of
this invention this exchange will occur with humid air entering the
chamber. In another aspect, residual air in the chamber is at least
partially removed by evacuation prior to running water vapor
through the chamber. As the water vapor is circulated between the
wetted surfaces and the sorbent material, it carries CO.sub.2 that
is released to the alkaline brine where it is absorbed into the
brine. In this implementation the resin functions to speed up the
transfer of CO.sub.2 from ambient air into the alkaline brine.
Further acceleration of the transfer of CO.sub.2 may be achieved
with other materials, such as, for example, with carbonic anhydrase
that thereby would open the use of brines with relatively low
levels of alkalinity e.g with a pH of 8-11. In this range one could
even use seawater, even though the accelerated acidification of
seawater would in many cases be counter-productive. However, this
would not be the case, for example, where the source of an alkaline
brine is an underground aquifer, from which brine is removed and to
which it is returned once the CO.sub.2 is absorbed. The brine could
also be water that has been exposed to alkaline mineral rocks such
as basalt or peridotite or serpentinite rock. For example, one
could percolate the water through a pile of serpentine tailings or
other tailings that can release alkalinity.
[0088] The use of serpentine tailings to increase alkalinity is
known in the art. Alternatively, the serpentine could be mined for
this purposes It also is possible in some formations to inject
water into alkaline underground systems for the purpose of
enriching it with base cations. The presence of CO.sub.2 in the
water may speed up this process.
[0089] In the case of serpentine and olivine as well as basalt,
this particular use of mineral sequestration would likely result in
the precipitation of magnesium and/or calcium carbonate. The
advantage of this method over previous attempts to directly
sequester CO.sub.2 from the atmosphere is that the CO.sub.2
concentrations can be enriched by about a factor of 100, which will
greatly help with the reaction kinetics.
[0090] Another source of alkalinity could be Mg(OH).sub.2 that has
resulted from the processing of serpentine and olivine.
[0091] It is also possible to use the CO.sub.2 to dissolve calcium
carbonate rock that then can be put into the ocean as calcium
bicarbonate. In this example it is possible to directly use
seawater to drive the dissolution, and the presence of carbonic
anhydrase may speed up this process dramatically. See, e.g. PCT
International Patent Appln. Serial No. PCY/US08/60672, assigned to
a common assignee, for a discussion of the use of carbonic
anhydrase to accelerate the CO.sub.2 capture process.
[0092] The dissolution of limestone with air captured CO.sub.2 is
analogous to a process in which the CO.sub.2 comes from a power
plant. The present invention provides a substantial advantage over
a power plant in that we do not have to bring enormous amounts of
lime stone to a power plant, or distribute the CO.sub.2 from a
power plant to many different processing sites, but that we can
instead develop a facility where seawater, lime and CO.sub.2 from
the air come together more easily. One specific implementation
would be to create a small basin that is periodically flushed with
seawater. The CO.sub.2 is provided by air capture devices located
adjacent to or even above the water surface. Of particular interest
are sites where limestone or other forms of calcium carbonate (such
as empty mussel shells) are readily available as well. If we have
calcium carbonate, seawater and air capture devices in one place,
we can provide a way of disposing of CO.sub.2 in ocean water
without raising the pH of the water.
[0093] Indeed, it is possible to install such units adjacent a
coral reef area by bringing additional limestone to the site or by
extracting limestone debris near the reef. If the units operate in
a slight ocean current upstream of the reef, they can generate
conditions that are more suitable to the growth of the coral reef
Growth conditions can be improved by raising the ion concentration
product of Ca.sup.++ and CO.sub.3.sup.--. This product governs the
rate of coral reef growth.
[0094] It should be emphasized that the above-described embodiments
of the present device and process, particularly, and "preferred"
embodiments, are merely possible examples of implementations and
merely set forth for a clear understanding of the principles of the
invention. Many different embodiments of the invention described
herein may be designed and/or fabricated without departing from the
spirit and scope of the invention. All these and other such
modifications and variations are intended to be included herein
within the scope of this disclosure and protected by the following
claims.
[0095] Therefore the scope of the invention is not intended to be
limited except as indicated in the appended claims.
* * * * *