U.S. patent application number 14/815661 was filed with the patent office on 2015-11-26 for carbon dioxide capture method and facility.
The applicant listed for this patent is Alessandro Biglioli, Mike Foniok, Brandon Hart, Kenton Heidel, David William Keith, II, Maryam Mahmoudkhani. Invention is credited to Alessandro Biglioli, Mike Foniok, Brandon Hart, Kenton Heidel, David William Keith, II, Maryam Mahmoudkhani.
Application Number | 20150336044 14/815661 |
Document ID | / |
Family ID | 41707678 |
Filed Date | 2015-11-26 |
United States Patent
Application |
20150336044 |
Kind Code |
A1 |
Keith, II; David William ;
et al. |
November 26, 2015 |
Carbon Dioxide Capture Method and Facility
Abstract
A carbon dioxide capture facility is disclosed comprising
packing formed as a slab, and at least one liquid source. The slab
has opposed dominant faces, the opposed dominant faces being at
least partially wind penetrable to allow wind to flow through the
packing. The at least one liquid source is oriented to direct
carbon dioxide absorbent liquid into the packing to flow through
the slab. The slab is disposed in a wind flow that has a non-zero
incident angle with one of the opposed dominant faces. A method of
carbon dioxide capture is also disclosed. Carbon dioxide absorbing
liquid is applied into packing in a series of pulses. A gas
containing carbon dioxide is flowed through the packing to at least
partially absorb the carbon dioxide from the gas into the carbon
dioxide absorbing liquid.
Inventors: |
Keith, II; David William;
(Calgary, CA) ; Mahmoudkhani; Maryam; (Calgary,
CA) ; Biglioli; Alessandro; (Calgary, CA) ;
Hart; Brandon; (Okotoks, CA) ; Heidel; Kenton;
(Calgary, CA) ; Foniok; Mike; (Calgary,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Keith, II; David William
Mahmoudkhani; Maryam
Biglioli; Alessandro
Hart; Brandon
Heidel; Kenton
Foniok; Mike |
Calgary
Calgary
Calgary
Okotoks
Calgary
Calgary |
|
CA
CA
CA
CA
CA
CA |
|
|
Family ID: |
41707678 |
Appl. No.: |
14/815661 |
Filed: |
July 31, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12545579 |
Aug 21, 2009 |
9095813 |
|
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14815661 |
|
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61090867 |
Aug 21, 2008 |
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Current U.S.
Class: |
95/212 ;
96/290 |
Current CPC
Class: |
Y02C 10/06 20130101;
Y02C 10/08 20130101; B01D 53/18 20130101; B01D 2251/604 20130101;
B01D 2251/304 20130101; B01D 2251/306 20130101; B01D 53/77
20130101; Y02C 10/04 20130101; B01D 2257/504 20130101; Y02C 20/40
20200801; B01D 53/1475 20130101 |
International
Class: |
B01D 53/14 20060101
B01D053/14; B01D 53/18 20060101 B01D053/18 |
Claims
1-22. (canceled)
23. A carbon dioxide capture facility for removing carbon dioxide
from ambient air, comprising: at least one liquid having a capacity
to absorb carbon dioxide; at least one packing material comprising
a plurality of flow passages, the packing material positioned to
receive an ambient air flow in a direction from a first opposed
dominant face, through the plurality of flow passages, and to a
second opposed dominant face opposite the first dominant face; at
least one fan positioned to influence flow of the ambient air
through at least a section of one of the first or second opposed
dominant faces of the packing material, the packing material
comprising a dimension between the first and second opposed
dominant faces that is parallel to the flow of the ambient air flow
between about 1 meter and about 15 meters, the fan positioned to
circulate the ambient air flow comprising atmospheric carbon
dioxide through the plurality of flow passages of the packing
material; at least one pump operable to apply the liquid over the
packing material at a first flow rate of the liquid during a first
portion of a time duration, the first portion comprising a
sufficient time duration to substantially replace a previous
portion of the liquid on the packing with a new portion of the
liquid that has a greater carbon dioxide absorption rate than the
previous portion of the liquid, the pump further operable to apply
the liquid over the packing material at a second flow rate of the
liquid applied during a second portion of the time duration, the
liquid operable to absorb a portion of the atmospheric carbon
dioxide at a predetermined duty cycle based on the time
duration.
24. The carbon dioxide capture facility of claim 23, wherein the
packing material is positioned such that the flow of the liquid
through the packing material is in a mean flow direction that is
parallel to a plane defined by the first and second opposed
dominant faces.
25. The carbon dioxide capture facility of claim 24, wherein the
packing material is positioned such that the flow of the liquid
through the packing material is in a mean flow direction that is
parallel to a plane defined by the first and second opposed
dominant faces comprises, and wherein the packing material is also
positioned to allow the liquid to flow through the packing material
by gravity.
26. The carbon dioxide capture facility of claim 24, wherein the
packing material is positioned such that the first and second
opposed dominant faces are vertically oriented.
27. The carbon dioxide capture facility of claim 23, wherein the
dimension between the first and second opposed dominant faces that
is parallel to the flow of the ambient air flow is between about 1
meter and about 3 meters.
28. The carbon dioxide capture facility of claim 23, wherein a
speed or a direction of the fan can be selectively controlled based
on a direction of wind incident on the packing material.
29. The carbon dioxide capture facility of claim 28, wherein the
fan comprises a part of a fan wall adjacent at least one of the
first or second opposed dominant faces of the packing material.
30. The carbon dioxide capture facility of claim 23, wherein a
plurality of modular structures containing the packing material are
connectively positioned in the carbon dioxide capture facility.
31. The carbon dioxide capture facility of claim 30, wherein each
modular structure comprises dimensions of about 5 meters by about 5
meters by about 7 meters, and the plurality of modular structures
are interconnected so as to result in a carbon dioxide capture
facility in which the packing material occupies a space having
dimensions of about 200 meters by about 20 meters by about 3
meters.
32. The carbon dioxide capture facility of claim 23, wherein the
liquid comprises a hydroxide solution.
33. The carbon dioxide capture facility of claim 32, wherein the
hydroxide solution comprises a sodium hydroxide solution.
34. The carbon dioxide capture facility of claim 23, wherein the
second flow rate is substantially zero.
35. The carbon dioxide capture facility of claim 23, wherein the
predetermined duty cycle is between about 1% and about 50% such
that the first portion of the time duration is between about 1% of
the time duration and about 50% of the time duration.
36. The carbon dioxide capture facility of claim 23, wherein the
fan is positioned to influence flow of the ambient air through at
least a portion of the packing material during the second portion
of the time duration.
37. The carbon dioxide capture facility of claim 23, wherein the
liquid and the packing material are configured to cooperatively
achieve a liquid holdup that provides an increased carbon dioxide
capture rate relative to the carbon dioxide capture facility
operating with the pump constantly at a flow rate substantially
equal to an average flow rate of the first and second flow
rates.
38. The carbon dioxide capture facility of claim 23, wherein the
first and second portions of the time duration are distinct in
value.
39. The carbon dioxide capture facility of claim 23, wherein the
pump is operable to circulate the liquid through a liquid
distributor system and to the packing material.
40. The carbon dioxide capture facility of claim 23, wherein the
packing material comprises structured packing.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of and claims priority to
U.S. application Ser. No. 12/545,579, filed on Aug. 21, 2009, which
claims priority to U.S. Provisional Application Ser. No.
61/090,867, filed on Aug. 21, 2008, both of which are incorporated
by reference in its entirety herein.
TECHNICAL FIELD
[0002] This document relates to gas-liquid contact systems and
methods, including carbon dioxide capture systems and methods for
the recovery of CO.sub.2 from atmospheric air.
BACKGROUND
[0003] To avoid dangerous climate change, the growth of atmospheric
concentrations of carbon dioxide must be halted, and may have to be
reduced. The concentration of carbon dioxide, the most important
greenhouse gas, has increased from about 280 ppm in the
preindustrial age to more than 385 ppm and it is now increasing by
more than 2 ppm per year driven by global CO.sub.2 emissions that
are now increasing at more than 3.3% per year (Canadell et al.,
2007).
[0004] Carbon capture and storage (CCS) technologies target
CO.sub.2 removal from large fixed-point sources such as power
plants. Dispersed sources, however, emit more than half of global
CO2 emissions. Direct capture of CO2 from ambient air, "air
capture", is one of the few methods capable of systematically
managing dispersed emissions. Therefore, while air capture is more
expensive that capture from large point sources it remains
important as it will primarily compete with emission reductions
from dispersed sources such as transportation which can be very
expensive to mitigate.
1.1 Air Capture
[0005] Carbon dioxide absorption from atmospheric air using
alkaline solution has been explored for half a century (Spector and
Dodge 1946, Tepe and Dodge 1943). Large scale scrubbing of CO2 from
ambient air was first suggested by Lackner in the late 1990's
(Lackner et al., 1999). In wet scrubbing techniques, CO2 is
absorbed into a solution of sodium hydroxide, NaOH, and is leaving
behind an aqueous solution of sodium hydroxide and sodium
carbonate, Na2CO3. For this process, the contactor, as the
component of the system that provides the contacts between CO2 and
sodium hydroxide, has thus far been a point of contention. Large
convective tower (Lackner et al., 1999), and packed scrubbing
towers (Baciocchi et al., 2006 and Zeman, 2007) are the most
commonly suggested contactor designs. A packed tower equipped with
Sulzer Mellapak has been proposed by Baciocchi et al. (2006) to
absorb CO2 from air with an inlet concentration of 500 ppm to an
outlet concentration of 250 ppm using a 2M NaOH solution.
[0006] An alternative strategy, suggested by Stolaroff et al.
(2007), is to generate a fine spray of the absorbing solution for
providing large surface to the air flow through an open tower. This
strategy could have the potential to operate with a small pressure
drop in air and avoids the capital cost of packing material.
Stolaroff et al. (2007) studied the feasibility of a NaOH
spray-based contactor by estimating the cost and energy requirement
per unit CO2 captured. Water loss, as a major concern in this
design, was addressed and it was found that the water loss could be
managed by adjusting of the NaOH concentration with temperature and
humidity of air, i.e. the higher the concentration of sodium
hydroxide, the lower is the water loss, e.g. using .about.7.2M
NaOH, at 15.degree. C. and 65% relative humidity, water loss is
eliminated.
[0007] Conventional scrubbing towers may be filled with structured
packing, and a flow of gas that is counter-current to the drainage
of liquid through the structured packing is employed.
SUMMARY
[0008] A carbon dioxide capture facility is disclosed comprising
packing formed as a slab, and at least one liquid source. The slab
has opposed dominant faces, the opposed dominant faces being at
least partially wind penetrable to allow wind to flow through the
packing. The at least one liquid source is oriented to direct
carbon dioxide absorbent liquid into the packing to flow through
the slab. The slab is disposed in a wind flow that has a nonzero
incident angle with one of the opposed dominant faces.
[0009] A method of carbon dioxide capture is also disclosed. Carbon
dioxide absorbing liquid is applied into packing in a series of
pulses. A gas containing carbon dioxide is flowed through the
packing to at least partially absorb the carbon dioxide from the
gas into the carbon dioxide absorbing liquid. The gas may flow
continuously, even while the liquid flows intermittently. In some
embodiments, the liquid and gas flow in a cross-flow geometry
relative to one another. For purposes of this disclosure
"cross-flow" means that the direction of the flow of gas relative
to the direction of the flow of liquid is orthogonal or
perpendicular.
[0010] A method of carbon dioxide capture is also disclosed. Carbon
dioxide absorbing liquid is flowed through packing in a mean liquid
flow direction. A gas containing carbon dioxide is flowed through
the packing obliquely or perpendicularly to the mean liquid flow
direction to at least partially absorb the carbon dioxide from the
gas into the carbon dioxide absorbing liquid.
[0011] A method of contacting a liquid with a gas is also
disclosed. The liquid is applied into packing in a series of
pulses, and the gas is flowed through the packing.
[0012] A method of contacting a liquid with a gas is also
disclosed. The liquid is flowed through packing in a mean liquid
flow direction. The gas is flowed through the packing obliquely or
perpendicularly to the mean liquid flow direction.
[0013] A gas-liquid contactor is also disclosed, comprising
packing, and at least one liquid source. The packing is formed as a
slab, the slab having opposed dominant faces, the opposed dominant
faces being at least partially wind penetrable to allow wind to
flow through the packing. The at least one liquid source is
oriented to direct the liquid into the packing to flow through the
slab. The slab is disposed in a wind flow that has a non-zero
incident angle with one of the opposed dominant faces.
[0014] A gas-liquid contactor is also disclosed comprising a slab
structure and a liquid source. The slab structure comprises
packing. The liquid source is oriented to direct the liquid into
the packing to flow in a mean liquid flow direction. The slab
structure is disposed in a wind flow that flows obliquely or
perpendicularly to the mean liquid flow direction.
[0015] A method of contacting a liquid with a moving gas is also
disclosed. The liquid is flowed through packing, and the moving gas
is driven through the packing in a drive direction that is at least
partially oriented with an ambient flow direction of the moving
gas.
[0016] The details of one or more non-limiting embodiments of the
invention, which may be encompassed by the claims, are set forth in
the drawings and the description below. Other embodiments of the
invention should be apparent to those of ordinary skill in the art
after consideration of the present disclosure. For example,
although this disclosure relates in particular to the removal of
carbon from ambient air, the methods and products described herein
can be readily adapated for removing other components, such as for
example SO.sub.x, NO.sub.x and fluorinated compounds, from ambient
air. A person of ordinary skill reading this specification would
understand what, if any, modification should be made in order to
capture the other components, for example in the choice of the
liquid source.
BRIEF DESCRIPTION OF THE FIGURES
[0017] Embodiments will now be described with reference to the
figures, in which like reference characters denote like elements,
by way of example, and in which:
[0018] FIG. 1 is a perspective view of a vertical slab
contactor.
[0019] FIG. 2 is a side elevation view, in section, of a horizontal
slab contactor.
[0020] FIG. 3 is a perspective view of the contactor of FIG. 2.
[0021] FIG. 4 is a top-down view of a series of carbon-dioxide
capture facilities with a central processing facility.
[0022] FIG. 5 is a perspective view, including a series of exploded
views thereof, of a horizontal slab contactor, partially in
section.
[0023] FIGS. 6 and 7 are graphs that illustrate the CO2 removal
from air passed through packing structured according to embodiments
disclosed herein and pumped with liquid absorbent at different NaOH
(FIG. 6) and KOH (FIG. 7) concentrations. Continuous flow is
indicated by the dots on the y axis, while capture efficiency after
a single pulse of flow is illustrated by the plotted lines.
[0024] FIG. 8 is a graph that illustrates the effectiveness of
pulsed pumping of the liquid absorbent through the packing, by
illustrating the CO2 removal per pulse at different NaOH
concentrations.
[0025] FIG. 9 is a side elevation view of a vertical slab contactor
with plural slabs.
DETAILED DESCRIPTION
[0026] U.S. 61/074,458 and the related U.S. Ser. No. 12/488,230 and
PCT PCT/US2009/047999 are hereby incorporated in its entirety by
reference.
[0027] The disclosure provides methods for removing carbon and/or
other components of air from ambient air, and devices for removing
ambient CO.sub.2 and/or other components of air from ambient
air.
[0028] In some embodiments, the method involves directing ambient
air using at least the energy of the wind, one or more fans, or
both through a contactor comprising a packing material;
intermittently flowing a carbon dioxide absorbing fluid over the
packing to achieve an average flow rate; and, capturing CO.sub.2
from the ambient air in the liquid such that either the carbon
dioxide capture rate is increased relative to a similar method in
which the liquid is constantly flowed at the average flow rate, or
the effectiveness of cleaning the surface of the packing material
is improved relative to a similar method in which the liquid is
constantly flowed at the average flow rate, or both.
"Intermittantly flowing" means flowing a fluid at a first rate that
is higher than at least one second rate (i.e. verying the flow of
the fluid through the contactor) resulting in an average flow rate,
wherein the at least one second rate can be zero. In some such
embodiments, the at least one second rate is zero, and
intermittently flowing produces a series of pulses.
[0029] In some embodiments, the method involves intermittently
flowing of a high molarity fluid through a contactor, and flowing
ambient air through the contactor, thereby capturing CO2 from the
ambient air. In some embodiments, the method involves
intermittently flowing a high molarity fluid through a contactor in
a cross-flow geometry relative to the direction of the flow of
ambient air, thereby capturing CO.sub.2 from the air. In some
embodiments, the method involves intermittently flowing a high
molarity fluid through a contactor in direction that is
substantially perpendicular to the direction of flow of ambient
air, thereby capturing CO.sub.2 from the air. In some embodiments
mentioned in this paragraph, "intermittently flowing" can be
implemented as pulsing the fluid through the contactor (over the
packing material). For example, repeatedly switching between
flowing the fluid briefly at a very high rate to evenly coat the
packing material and shutting off the fluid flow for a duration of
time.
[0030] In some embodiments, the device is a carbon (or other
ambient air component) capture facility including at least one
liquid having a capacity to absorb carbon dioxide (or other ambient
air component); at least one packing material having a hold up
relative to the liquid; and, at least one pump for flowing the
liquid over the packing material, the pump being configured to
deliberately vary the flow rate to produce an average flow rate,
wherein the capacity of the liquid and the holdup of the packing
material are chosen to either cooperatively achieve an increased
carbon dioxide capture rate relative to a similar carbon dioxide
capture facility in which the pump is operated constantly at the
average flow rate, or to improve the effectiveness of cleaning of
the surface of the packing material relative to a similar carbon
dioxide capture facility in which the pump is operated constantly
at the average flow rate, or both.
[0031] In some embodiments the carbon capture facility comprises a
packing material having sufficient hold up that it can be
intermittently wetted with a CO.sub.2 (or other ambient air
component) capture solution, and the capture facility has a
vertical slab geometry. In some embodiments, the capture facility
comprises a packing material capable of being intermittently wetted
and used in a cross-flow geometry, and the capture facility has a
vertical slab geometry. In some embodiments, the capture facility
comprises a packing material capable of being intermittently wetted
and used in a substantially perpendicular geometry, and the capture
facility has a vertical slab geometry. In some embodiments, the
capture facility further comprises a device for removing dust
contamination, for example structural stilts which can lift the
capture facility off the ground, for example at least about 5 m off
of the ground so that dust blows underneath the facility.
[0032] The carbon capture facility can be built up in modules, such
as for example illustrated in FIG. 1. As an example, each module
can have dimensions of about 5 m by about 5 m by bout 7 m. The
modules contain packing and can support a fan. Once the modules are
assembled to form the carbon capture facility, the packing material
can ultimately occupy dimensions of about 200 m by about 20 m by
about 3 m. The modules can be built from steel. The final structure
can include a sump at the base which has fluid. A pump is
configured to periodically moe the fluid from the supm to a
distributor at the top of the packing. The gas phase is moved
through the packing by the wind, fans, or a combination thereof. In
the illustrated embodiment, each module supports a fan, resulting
in a wall of fans.
[0033] "Packing" is a material that fills a space and facilitates
the contact between a gas stream and a liquid stream. Packing can
be random or structured. Random packing comprises small shapes
formed out of a suitable material and dumped into the space where
contact between liquid and gas is to occur. Structured packing is
any packing which is designed to be fitted into an area in a
systematic and planned manner that results in a specific flow
pattern for both air and liquid.
[0034] In some embodiments, packing suitable for use within the
scope of the disclosure has: a cross flow geometry designed to
limit or minimize the pressure drop in air per unit CO2 extracted;
can be efficiently wetted by intermittent liquid flows; and, has a
liquid hold up enabling intermittent operation with long time
durations between wetting.
[0035] In some embodiments, packing suitable for use within the
scope of the disclosure can tolerate manufacturing flaws, i.e. even
significant portions of the packing material are not wetting. For
purposes of this disclosure, in this context, "significant" means
beyond the valued normally considered acceptable for structured
packing. In some embodiments, packing suitable for use within the
scope of the disclosure can include flaws or dead spots which are
not wetted, as long as such dead spots do not significantly
increase drag per unit CO.sub.2 captured, or in other words the
effect of the dead spots would not impact the overall cost per ton
of CO.sub.2 captured when both capital and operating costs are
considered to an extent that would deter use of the packing
material. In some embodiments, the effect of the dead spots would
not increase the overall cost per ton of CO.sub.2 captured when
both capital and operating costs are considered. In some
embodiments, packing suitable for use within the scope of the
disclosure includes up to about 10% dead spots or flaws. The use of
packing with flaws or gas parts may reduce capital cost of the
packing.
[0036] In some embodiments, packing material suitable for use in
accordance with the disclosure is readily cleaned of airborne
contaminants. In some embodiments, cleaning should take advantage
of intermittent flow.
[0037] In some embodiments, packing suitable for use in carbon
capture facilities within the scope of the disclosure are designed
for liquid hold up, have a low resistance to the gas flow (e.g.
about 100 Pa at gas flows of 2 m/s or less), and/or can be flushed
by intermittent wetting.
[0038] In some embodiments, the packing material can be chosen from
low-density commercial structured packing Without being bound by
theory, low density commercial structured packing, which is packing
having a high void fraction, is thought to have a large area for
the gas phase to pass through favorably impacting (i.e. reducing)
the pressure drop across the packing relative packing with a lower
void fraction. A reduction in pressure drop is thought to lead to a
decrease in the amount of energy consumed when moving the gas phase
through the packing Non-limiting examples of suitable packing
materials include Bretwood AccuPak CF-1200, Brentwood XF74, Sulzer
250X, Sulzer I-ring, Montz-Pak type M.
[0039] A "vertical slab" refers to a layout of packing in which the
dimension parallel to gas flow is smaller than the dimensions
perpendicular to the gas flow. For example, in some embodiments,
the thickness of the vertical slab (which is dimension parallel to
the air flow) is about 3 m, whereas the other two dimensions are
about 200 m (length) and 20 m (height).
[0040] The liquid, or CO.sub.2 capture solution, which is used with
the carbon capture facility, can be any liquid that can remove at
least some CO.sub.2 from ambient air. In some embodiments, a basic
solution is used. In some embodiments, a KOH or a NaOH solution is
used. In some embodiments, the KOH solution has a molarity ranging
from less than 1 molar to about 6 molar. In some embodiments, the
NaOH solution has a molarity ranging from less than 1 molar to
about 6 molar. The molarity of the solution can be chosen based on
a number of factors, including location, packing structure,
operating conditions, equipment and value of CO.sub.2 captured. In
general, the liquid is chosen to have a sufficient capacity to
absorb CO.sub.2 per unit volume to enable intermittent flow or
wetting of the packing material.
[0041] Prior to this disclosure, it was believed that a packed
tower, counterflow geometry should be used for ambient carbon
dioxide capture. See, e.g., H. Herzog, "Assessing the Feasibility
of Capturing CO.sub.2 from the Air" (MIT Laboratory for Energy and
the Environment, 2003). Contrary to the conventional wisdom, it has
been shown that in some embodiments, the carbon capture facilities
provide an improvement in one or more of operating costs, capital
costs, and pressure drops (anywhere other than at the packing)
relative to conventional ambient air carbon capture facilities
comprising a packing material but having a cylindrical, tower
geometry using a counterflow design, specifically the tower
geometry carbon capture facility described in
[0042] In some embodiments, operating costs are improved by
improving energy extraction from ambient wind to reduce energy use,
for example by orienting the contactor to get the most energy from
the wind, wherein the orientation is a function of wind directions
and air handling equipment. In some embodiments, the slab is
oriented so that the direction of the prevailing wind is not
parallel to the direction of flow of the carbon capture solution
through the packing material (i.e. the direction of the prevailing
wind is not parallel to the orientation of the slab). In some
embodiments, improved energy extraction from ambient air is
accomplished using a cross-flow design. In some embodiments, the
direction of the prevailing winds relative the orientation of the
slab ranges from about 80 degrees to about 100 degrees. In general,
the orientation would be chosen to minimize the annual average fan
power depending on the wind rose and local geography. In some
embodiments, the direction of the prevailing winds relative to the
orientation of the slab is about 90 degrees.
[0043] In some embodiments, operating costs are improved by
intermittently wetting, rather than continuously dripping, the
packing material with carbon capture liquid. In some embodiments,
the carbon capture liquid is pulsed having a duration sufficient to
wash the somewhat spent solution which is capturing CO2 at a
reduced rate off the packing and replace it with fresh solution
that will capture CO2 at a faster rate. In some embodiments, the
time between pulses is chosen to reduce or minimize the cost of CO2
capture, taking into account both the energy required to operate
the system and the cost of capital used to build the system. In
some embodiments, in which the packing has in inlet surface area
for the gas of about 200 m.times.20 m and a thickness of about 3 m,
the duration of a pulse can range from about 30 to about 60 seconds
and the time between pulses can range from about 1 to about 20
minutes. In some embodiments, the duration of a pulse can range
from about 60 to about 200 seconds and the time between pulses can
range from about 1 to about 20 minutes. In some embodiments, the
pump would be on for 150 seconds and off for 240 seconds
[0044] In some embodiments, capital costs are reduced by reducing
the footprint and total structure size per unit of capacity.
[0045] Low energy contactor for CO2 capture from air. Some
embodiments disclosed in this document link three concepts: [0046]
1. That low-density commercial structured packings combined with
high-molarity caustic solutions exhibit sufficiently low pressure
drops to make them cost effective for air capture. [0047] 2. When
used with high-molarity caustic solutions such packings may be
operated using intermittent fluid flow. High fluid flows (i.e.
fluid flows matching the specifications provided by the
manufacturer) can be used to wet the surface which then exhibits
sufficient `hold up` to enable it to capture CO2 from air for 100's
of seconds with minimal loss of capture efficiency. This operation
mode can improve the overall energy efficiency by factors of three
or more as compared to conventional counterflow tower geometries
because the fluid pumping work is essentially eliminated. In some
embodiments, "minimal loss of capture efficiency" can be
demonstrated by an uptake rate decrease of less than 30% in a time
span of minutes. Packing manufacturers claim that if the solution
flow drops below a certain threshold (different for each type of
packing) the contact between the solution and the gas will
drastically drop with the result in many situations of the uptake
rate dropping by a factor of 10 up to a factor of 100. However, in
embodiments in accordance with the disclosure, packing can be
wetted using the flows suggested by the manufacturer's
specifications but then the flow can be shut off and the uptake
rate decreases by less than 30% in a time span of minutes. [0048]
3. Configurations of large-scale contactors that have high ratios
of packing area to total footprint and that interact with the
ambient air so as to minimize or reduce recycling of low-CO2 air
into the contactor inlet. If a rectangular array of conventional
packed towers were built then the air exiting one unit which has a
lower than ambient concentration of CO.sub.2 would be sucked into
the toward downwind of it. This tower would then experience a
reduced CO.sub.2 capture rate but it would still be costing as much
to run it as the first tower. In any array of standard packed
towers (other than a line of them) this would affect a large
portion of the towers and decrease the overall facilities capture
of CO.sub.2 with no change in operating costs. If the cost to own
and run the system is constant but the capture rate drops then the
cost per captured CO.sub.2 increases. Slab` contactor geometries
will have much lower capital costs per unit of air scrubbing
capacity than could be achieved with conventional `tower`
geometries.
[0049] Referring to FIGS. 6-8, there is provided laboratory data
that demonstrates the first two ideas. This data illustrates that
commercial structured packing (e.g., Sultzer 250 X) can be operated
with high molarity NaOH or KOH, for example, flowing in pulses that
amount to less than, for example, 10% of full time (for example
operating at the design fluid flow rate for about 30 seconds and
then no fluid flow for about 600 seconds) while achieving >80%
of the capture rate achieved with the design fluid flow rates. The
data would enable one to choose the optimal cycle time for specific
contacting fluids and packing, and will provide a basis for
improving packing designs for this application.
[0050] Referring to FIGS. 6-8, disclosed is data on the performance
of both NaOH and KOH solutions at a wide range of concentrations in
using both continuous and intermittent flow. For any of the
embodiments illustrated herein, the total mechanical work
requirement may be less than 100 kWhr/t-CO2 at capture rates
greater than 20 t-CO2/m2-yr. Whereas vertical slab geometry is
emphasized in portions of this disclosure, disclosed as embodiments
herein are two slab-geometry contactors: Vertical slab geometry
(FIG. 1), and horizontal slab geometry (FIGS. 2, 3, and 5). It
should be understood that the disclosed embodiments are provided
for the purpose of illustration and should not be construed as
limiting in any way.
[0051] Referring to FIG. 1, a carbon dioxide capture facility 10 is
illustrated comprising packing 12 formed as a slab 15, the slab 15
having opposed dominant faces 14, the opposed dominant faces 14
being at least partially wind penetrable to allow wind to flow
through the packing 12. At least one liquid source 16 is oriented
to direct carbon dioxide absorbent liquid into the packing 12 to
flow through the slab 15. The slab 15 is disposed in a wind flow 18
that has a non-zero incident angle with one of the opposed dominant
faces 14. The packing 12 may be oriented to direct the flow of
carbon dioxide absorbent liquid through the slab 15 in a mean flow
direction 20 that is parallel to a plane 22 defined by the opposed
dominant faces 14. It should be understood that opposed dominant
faces 14 don't have to be exactly parallel. In one embodiment, the
faces 14 may be converging, diverging, or curved for example.
Packing 12 may be oriented to allow the carbon dioxide liquid
absorbent to flow through the packing 12 by gravity, as
illustrated. In some embodiments, packing dimensions can be about
200 m.times.about 20 m by about 3 m contained in a structure
measuring about 200 m.times.25 m.times.7 m. In some embodiments,
dimensions can range from about 10 m.times.about 7 m.times.about 2
m to about 1000 m.times.about 50 m.times.about 15 m.
[0052] Referring to FIG. 1, the non-zero incident angle refers to
the fact that wind flow 18 strikes the face 14 at an angle greater
than zero. This may be contrasted with traditional packing
arrangements, where gas is flowed through a tower of packing
starting from the very bottom. In some embodiments, the non-zero
incident angle is orthogonal with the one of the opposed dominant
faces. It should be understood that the non-zero incident angle may
be within 10% of exactly orthogonal. The non-zero incident angle
may also refer to the mean angle of flow of the wind. The mean
angle of flow of the wind may be averaged over a period of
time.
[0053] Referring to FIG. 2, in some embodiments, the packing 12
further comprises structured packing. The packing 12 may be, for
example, 1-2 meters thick between the opposed dominant faces 14. In
other embodiments, the packing 12 may be thicker or thinner. The
term structured packing may refer to a range of specially designed
materials for use in absorption and distillation columns and
chemical reactors. Structured packings typically consist of thin
corrugated material 24, such as metal plates or gauzes arranged in
a way that they force fluids to take complicated paths through the
column, thereby creating a large face area for contact between
different phases. Structured packings may be made out of corrugated
sheets arranged in a crisscrossing relationship to create flow
channels for the vapor phase. The intersections of the corrugated
sheets create mixing points for the liquid and vapor phases. Wall
wipers are utilized to prevent liquid and/or vapor bypassing along
the column wall. Rotating each structured packing layer about the
column axis provides cross mixing and spreading of the vapor and
liquid streams in all directions.
[0054] Referring to FIG. 1, the opposed dominant faces 14 may be
oriented vertical. The orientation of faces 14 may be determined
relative to, for example, the ground. In other embodiments, faces
14 may be oriented at an angle to the ground, ie slanted. Referring
to FIG. 5, the opposed dominant faces 14 may be oriented
horizontal. This embodiment tends to have a larger footprint than
the vertical slab embodiment. Referring to FIG. 9 the packing 12 is
formed as plural slabs 15. Plural slabs may also be, for example,
by plural slabs arranged end-to-end, as opposed to the stacked
orientation illustrated in FIG. 9. In some embodiments, the slab
might be vertically sectionalized, effectively providing plural
slabs end to end on top of one another. This may be required in
order to get sufficiently good distribution of liquid in such a
narrow aspect ratio (e.g., 20 m high by 1.5 wide). Between the
vertical sections there may be a collector/distributor system that
collects fluid flowing from above and redistributes it evenly to
the packing slab below. In some embodiments, such a
collector/distributor system may be present in any slab as
disclosed herein.
[0055] Referring to FIG. 1, the at least one liquid source 16 may
further comprise at least one pump 26. Pump 26 may have several
distribution pipes 28, controlled by a valve (not shown), in order
to selectively apply liquid into various sections of packing 12.
The at least one pump 26 may be configured to supply the carbon
dioxide absorbent liquid in a series of pulses.
[0056] Referring to FIG. 1, at least one fan 30 may be oriented to
influence wind flow through at least a section of one of the
opposed dominant faces 14 of the packing 12. Fan 30 may be
reversible. In some embodiments, fan 30 may prevent the wind flow
that has already flowed through the packing 12 from circulating
back into the packing 12. Referring to FIG. 5, in some embodiments,
at least one fan 30 may drive the wind flow into packing 12.
Referring to FIG. 1, the at least one fan 30 may further comprise
plural fans, each of the plural fans being oriented to influence
wind flow through at least a respective portion of the packing 12.
In some embodiments, the respective portion is understood as being
the portion of the packing 12 that air flow through fan 30 would
have the greatest influence over, for example the packing 12 most
adjacent or closest to fan 30. The at least one fan 30 may provided
as part of a fan wall 32 adjacent at least one of the opposed
dominant faces 14. It should be understood that fan walls (not
shown) may be located adjacent each of faces 14. Adjacent, in this
document, is understood to mean next to, and can include
embodiments (such as the one illustrated in the Figures) where the
fan wall 32 is spaced from, but adjacent to, face 14. Referring to
FIG. 1, the fan wall 32 may be adjacent the one of the opposed
dominant faces 14 through which the wind flow 18 is exiting the
packing 12. In fan wall 32, the individual fans may be separated by
impermeable material. The fans 30 create a pressure drop across the
wall 32, which drives flow through the packing 12. In some
embodiments, fan wall 32 is designed such that, in the event that a
fan fails, and ultimately blocks of its respective flow, flow
through the packing 12 would be almost, if not completely,
unaffected. This may be accomplished by closely spacing adjacent
fans, and by spacing the fan wall 32 from the packing 12, for
example.
[0057] Referring to FIG. 2, facility 10 may further comprise wind
guides 34 oriented to direct the flow of wind 18 into the packing
12. Facility 10 may further comprise wind guides 36 oriented to
direct the flow of wind 18 out of the packing 12. Wind guides 34
and 36 may be, for example, louvers. As illustrated in FIG. 2, the
wind guides 34 and 36 may be independently controllable. In the
embodiment of FIG. 2, wind flow 18 is directed from the right to
the left. Thus, the upper wind guides 34 are open, with the lower
wind guides 34 closed. Similarly, upper wind guides 36 are closed,
while lower wind guides 36 are open. Thus, wind flow 18 has a net
flow from upper wind guides 24 to lower wind guides 36, passing
through packing 12 in the process. Referring to FIG. 2, facility 10
may be part of an at least partially enclosed structure 38. Because
of the nature of the embodiments disclosed herein, that being that
they may involve the processing of great deals of wind, it may be
important to shield facility 10 from the elements, including
animals and insects. Wind guides 36 and 34 may aid in this, along
with a surrounding structure adapted to selectively let in and
process wind flow. In some embodiments, a protective covering (not
shown) may be provided over packing 12 to prevent animal intrusion
but allow wind flow to pass through. Referring to FIG. 1, a
cleaning device 40 for cleaning the walls of the at least partially
enclosed structure 38 may be provided. Cleaning device 40 may be,
as illustrated for example, a wiper that rotates about an axis to
clean the exterior of fan wall 32, for example. Wind guides 34 and
36 may be horizontally oriented, for example.
[0058] Referring to FIG. 2, facility 10 may further comprise at
least one wind passage 42 extended through the opposed dominant
faces 14 to deliver wind flow selectively to one of the opposed
dominant faces 14. Referring to FIG. 2, wind passage 42 may have
fan 30 attached to influence air flow through wind passage 42. Wind
passage 42 allows wind to travel through faces 14, where it is
released into basin 44, where the wind is free to pass into packing
12 through face 14A, exiting the packing 12 through face 14B. This
way, wind flow may be induced to flow through the horizontal faces
14 of a horizontal slab of packing 12. Wind passages 42 may be, for
example, air ducts that are 10 m in height. In the embodiment
illustrated, wind passages 42 are vertical ducts in which CO2 rich
inlet air is moving down. These ducts may cover .about.1/5 of the
surface area (e.g., .about.1.2 m diameter tube arranged in a grid
with 5 meter spacings.).
[0059] Referring to FIG. 1, a sink 46 may be provided for
collecting carbon dioxide absorbent liquid that has flowed through
the packing 12. Referring to FIG. 2, the sink is illustrated as
basin 44. Basin 44 may be, for example a concrete-lined basin that
catches the hydroxide and contains supports to hold the packing
Referring to FIG. 5, there may be a gap 60 as illustrated between
the packing 12 and the base 44 that can be .about.1 to 1.5 m for
example. In some embodiments (not shown), sink 46 may be a pipe or
a series of conduits for example, that transport the liquid
directly from packing 12. This type of system may involve a
funneling or drainage apparatus designed to focus the drainage of
the liquid into a single, or a network of pipes. The contacted
liquid may then be recirculated through the packing, or it may be
recycled and then recirculated. Referring to FIG. 4, in some
embodiments, facility 10 further comprises a recycling system 48
for regenerating spent carbon dioxide absorbent liquid. The
recycling system may be, for example, any of the systems disclosed
in Appendix A, which forms part of this specification, for
recycling spent carbon dioxide liquid absorbent. As disclosed in
Appendix A, the carbon dioxide absorbent liquid may comprise a
hydroxide solution, for example a sodium hydroxide solution. The
source of liquid 16 preferably supplies recycled carbon dioxide
absorbent liquid.
[0060] Referring to FIGS. 1 and 2, a method of carbon dioxide
capture is illustrated. Carbon dioxide absorbing liquid is applied
into packing 12 in a series of pulses. Referring to FIG. 9, each
pulse 50 may involve, for example, a short period during which the
liquid is supplied into packing 12 by source of liquid 16. Each
pulse doesn't have to be a sharp transient application, but can be
a period of time during which liquid is being supplied. A gas
containing carbon dioxide, for example air illustrated by flow of
wind 18, is flowed through the packing 12 to at least partially
absorb the carbon dioxide from the gas into the carbon dioxide
absorbing liquid. Applying may further comprise pumping. Flowing
may further comprise flowing the gas containing carbon dioxide
through the packing at least when the carbon dioxide absorbing
liquid is not being applied. Referring to FIG. 1, the flow of gas
may be controlled using fans 30, for example. Referring to FIG. 2,
the flow of gas may be controlled using fans 30 and wind guides 34
and 36. Referring to FIGS. 1 and 2, the flowing of the gas may be
at least restricted when the carbon dioxide absorbing liquid is
being applied. Referring to FIG. 1, this may be envisioned by the
fans 30 of fan wall 32 ceasing to spin and draw the flow of wind
through packing 12 when the pulse of liquid is being supplied to
packing 12.
[0061] In some embodiments, the series of pulses has a duty cycle
of 1-50%. In other embodiments, such as the one illustrated
graphically in FIG. 9, the duty cycle may be 5% for example. The
duty cycle refers to the ratio of the time duration of a pulse of
applied liquid to the overall time duration of a cycle. For
example, a 50% duty cycle implies the fluid is only flowing half
the time the facility is operational. This means the pulse runs
from 1 to 50% of the time the system is operational, and therefore
a 1% duty cycle means that for every second that fluid is flowing
is off for 100 seconds. In more realistic values, it is on for 30
seconds and off for 3000 seconds and a 50% duty cycle means the
pump would run for 30 seconds and be off for the next 30 seconds.
In some embodiments, the series of pulses has an off-time of
10-1000 seconds. In other embodiments, the series of pulses has an
off-time of 100-10000 seconds.
[0062] Referring to FIG. 1, the step of applying may further
comprise applying the carbon dioxide absorbing liquid into a first
portion of the packing 12 in a first series of pulses, and applying
the carbon dioxide absorbing liquid into a second portion of the
packing 12 in a second series of pulses. This may be envisioned by
selectively applying liquid via distribution tubes 28A and 28B to
packing 12. Because tubes 28A and 28B only feed a portion (ie the
left-most portion) of packing 12, only that portion will have
liquid applied to it. Liquid may then be selectively applied to the
right hand portion of packing 12 by applying liquid via tubes 28C
and 28D. The first and second series of pulses may be synchronized,
asynchronized, completely different, or synchronized out of phase
with one another, for example, allowing fluids to be supplied
intermittently from a continuously operating pump. In these
embodiments, flowing the gas may further comprise at least
restricting the flow of the gas containing carbon dioxide through
the first portion of the packing when the carbon dioxide absorbing
liquid is not being applied, and at least restricting the flow of
the gas containing carbon dioxide through the second portion of the
packing when the carbon dioxide absorbing liquid is not being
applied. Thus, while the first portion has liquid being applied to
it, for example the left hand portion of face 14 when liquid is
being applied via tubes 28A and 28B, the flow of gas may be
restricted or stopped altogether through the left hand portion of
face 14. This may be accomplished by reducing, stopping, or even
reversing fans 30A and 30B, for example. Similarly, while the
second portion has liquid being applied to it, for example the
right hand portion of face 14 when liquid is being applied via
tubes 28C and 28D, the flow of gas may be restricted or stopped
altogether through the right hand portion of face 14. This may be
accomplished by reducing, stopping, or even reversing fans 30D and
30E, for example.
[0063] In some embodiments, the first series of pulses and the
second series of pulses are staggered. Referring to FIG. 2, this
may be advantageous, as when the left portion of face 14 has liquid
being applied to it as described above, the right hand portion and
center portions do not. Similarly, when the supply of liquid to the
left hand portion is ceased, the source of liquid 16 may then apply
liquid to the center or right hand portion, for example. This way,
source of liquid 16 may cyclically feed liquid to the entire volume
of packing 12 in a more efficient manner, instead of continuously
feeding liquid to the entire volume of packing 12. Referring to
FIG. 5, an example of this may be further envisioned, with a
horizontal slab of packing 12. In this embodiment, the flow of wind
through any of the various wind tubes 42 may be controlled, in
order to achieve the same effect as that achieved above with the
vertical slab embodiment. Referring to FIG. 2, an embodiment is
illustrated where only one wind tube 42A has wind being driven down
it. This may be achieved by the selective actuation of fan 30A, for
example. Thus, the packing 12 that is nearest the outlet of wind
tube 42A may have a flow of gas fed to it.
[0064] In some embodiments, the off-cycle of the series of pulses
may be less than or equal to the time it takes for carbon dioxide
absorbing liquid to stop draining from the packing after a pulse.
It should be understood that this is not the time required for the
entire pulse to be removed from the packing 12, since some liquid
will always be left over as residue inside the packing 12. In other
embodiments, the off-cycle of the series of pulses may be less than
or equal to the time it takes for a pulse of carbon dioxide
absorbing liquid to lose 70-80% of the pulses carbon dioxide
absorption capacity.
[0065] Referring to FIG. 1, the packing may be oriented to flow the
carbon dioxide absorbing liquid through the packing 12 in a mean
liquid flow direction 20. Flowing may further comprise flowing the
gas through the packing 12 obliquely or perpendicularly to the mean
liquid flow direction 20. As disclosed above, this is advantageous
as the flow of gas my have a different flow direction than, and one
that is not counter current to, the mean liquid flow direction 20
of the liquid. Thus, a larger surface area of the packing may be
used to full advantage, greatly increasing the quantity of wind or
gas that may contact liquid in packing 12 over a course of time
while still allowing the liquid to pass through and drain from
packing 12. In these embodiments, a slab is not entirely necessary,
in fact other shapes of packing 12 are envisioned, including but
not limited to a cube, a cylindrical, and other various shapes.
Referring to FIG. 1, in some embodiments flowing the gas further
comprises flowing the gas through the packing 12 perpendicularly to
the mean liquid flow direction 20. It should be understood that
exact perpendicularity is not a requirement. Flowing may further
comprise flowing the gas through at least one of the opposed
dominant faces 14, for example through both of faces 14 as
indicated.
[0066] As disclosed above, these methods may involve recycling the
carbon dioxide absorbing liquid. Also as disclosed above, the
methods may involve influencing the flowing of the gas through the
packing. Influencing may comprise, for example, preventing the gas
that has already flowed through the packing 12 from circulating
back into the packing 12. Influencing may further comprise driving
the flowing of the gas in a drive direction that is at least
partially oriented with an ambient wind flow direction. This may be
carried out using fans 30, which may be reversible in order to
carry out this function. Further, these methods may involve
directing the flow of gas at least one of into and out of the
packing, using, for example louvers as already disclosed.
[0067] Referring to FIG. 1, in some embodiments, fans 30 may be
reversible in order to enable the flow to be driven in the
direction of the ambient wind field, which is more efficient than
inducing a flow that is counter to the prevailing wind direction.
Referring to FIG. 4, the orientation of slabs 15 may be such that
prevailing wind 18 is perpendicular to the slab 15, and is in the
direction at which the fan wall (not shown) works most efficiently.
The packing design may use vertically oriented plates. This would
be a modification of conventional structured packing designed to
enable, for example, orthogonal liquid and gas flow directions.
Packing may be for intermittent fluid flow so as to maximize the
hold up of liquid absorbent inside the packing material. Referring
to FIG. 1, as disclosed above, the fan wall 32 may be
sectionalized, so that flow speed can be reduced or stopped when
fluid is flowing to minimize fluid loss. The sections may be
operated asynchronously so that only one section at a time is
receiving the fluid flow enabling fluid pumps to operate
continuously. For example, if fluid flow was needed for 100 seconds
out of 1000 one may have 11 sections and would direct the fluid
into one of them at a time.
[0068] Compared to the horizontal slab geometry, the vertical slab:
minimizes the footprint and the total structure size per unit of
capacity to reduce the capital cost, reduces peak velocity,
improving efficiency, and enables the packing to be operated at
higher peak velocities further reducing capital costs.
[0069] As disclosed above, some embodiments may invoke the use of
louvers to enable the flow to be driven in the direction of the
ambient wind without altering the operation of the fans. Referring
to FIG. 5, the packing design may using coaxial flow or counter
current flow, while still benefiting from the larger surface area
of the slab to increase the amount of wind flow through the slab.
The flow geometry allows one to get even flow though a large
horizontal slab mounted just above a fluid reservoir while
maintaining air speeds below about 5 m/sec. The air speed
constraint determines the ratio of the structures height to its
width. Specifically, height/width is approximately equal to
airspeed-at-packing/air-speed-at-exit. Compared to the vertical
slab geometry, the horizontal slab has a larger footprint, and may
have higher costs, but it has the advantage that it may use more
conventional packing and fluid distribution.
[0070] Referring to FIG. 4, a rough sketch is illustrated showing a
mile X mile grid (eg. roads on a North American prairie) with 8
capture units each having, for example, 300.times.50 m footprint
facilities 10 and a central processing station 48 with connecting
pipelines 56. A system of this magnitude would be expected to
capture 1-5 megatons CO.sub.2 per year.
[0071] Referring to FIG. 3, a view of a full unit, for example 50 m
wide, by 300 long, by 20 m high is illustrated. In some
embodiments, the height of the slabs may be 10-30 m. If the wind
was blowing from the right to left, one would open the louvers so
that inlet air flowed in on the lower right and out the upper left.
(This is the opposite of what is shown in the cross section
illustrated in FIG. 2). The roof 58 may be rough, like the zig-zag
design shown here which is structurally efficient. In some
embodiments, the roof 58 need not keep water out, it need only be
proof against wind loads. Referring to FIG. 5, the source of liquid
may be, for example a fluid distribution system on top of packing
12.
[0072] Referring to FIG. 1, another method of carbon dioxide
capture is illustrated. Carbon dioxide absorbing liquid is flowed
through packing 12 in a mean liquid flow direction 20, a gas
containing carbon dioxide is flowed through the packing 12
obliquely or perpendicularly to the mean liquid flow direction 20
to at least partially absorb the carbon dioxide from the gas into
the carbon dioxide absorbing liquid. Flowing carbon dioxide
absorbing liquid through packing 12 may further comprise applying
the carbon dioxide absorbing liquid into the packing 12 in a series
of pulses. The series of pulses has been disclosed in detail
throughout this document, and need not be built upon here. As
disclosed above, flowing the gas further may comprise flowing the
gas through the packing 12 perpendicularly to the mean liquid flow
direction 20.
[0073] A method of contacting a liquid with a gas is also disclosed
comprising applying the liquid into packing 12 in a series of
pulses and flowing the gas through the packing 12. Referring to
FIG. 8, after the pulse 50 has been applied, the downward slope of
each of the profiles indicates that CO.sub.2 is still being
absorbed by the slowly draining or stagnant liquid. This
illustrates that this packing 12 design is highly efficient,
because it continues to effectively contact gas and liquid, without
the need for constant pumping. Referring to FIGS. 6 and 7, the
capture efficiency of CO.sub.2 is illustrated and contrasted for
continuous flow (indicated by the dots on the y axis), and for a
single pulse of flow (illustrated by the plotted lines). The time
scale is time after the flow has been shut off for the pulsed flow.
The downward sloping lines show the gradual drop off in capture
efficiency over 200-1000 seconds, but illustrate that the liquid
still has a high capture efficiency, even after hundreds of seconds
have passed. While this method is also envisioned for some of the
embodiments herein, it is not as efficient as the pulsed method, as
it requires far greater pumping action. Thus, the pulsed method may
be applied to any gas-liquid contactor, because it has been proven
herein to afford sufficient gas-liquid contact despite a lack of
continuous pumping. An exemplary application of this may be
provided as a scrubbing unit at a refinery, for example. It should
be understood that the gas-liquid contactor may have all of the
same characteristics as the carbon dioxide capture facility as
disclosed herein.
[0074] Further disclosed is a method of contacting a liquid with a
gas comprising flowing the liquid through packing in a mean liquid
flow direction, and flowing the gas through the packing obliquely
or perpendicularly to the mean liquid flow direction. This method
may be envisioned as carried out by the embodiments in the figures.
Similar to the gas-liquid contactor, the results from FIGS. 6-8
confirm that this method may be applied to any gas-liquid contact
system. By having the gas flowed through the packing at an angle,
the structure of such a contactor employing this method would be
greatly simplified, since the gas inlet and outlet will be at
different locations in the packing then the liquid source and sink.
This is in contrast to previous systems which supply gas in a
counter-current direction to the liquid flow. It should be
understood that this method may have all of the same
characteristics as the carbon dioxide capture methods disclosed
herein. For example, flowing the liquid through the packing may
further comprise applying the liquid into the packing in a series
of pulses. Furthermore, flowing the gas may further comprise
flowing the gas through the packing perpendicularly to the mean
liquid flow direction.
[0075] Referring to FIG. 1, a gas-liquid contactor (illustrated by
facility 10) is also disclosed. Referring to FIG. 1, the contactor
(illustrated as facility 10) comprises packing 12 formed as a slab
15, the slab 15 having opposed dominant faces 14, the opposed
dominant faces 14 being at least partially wind penetrable to allow
wind to flow through the packing 12. At least one liquid source 16
is oriented to direct the liquid into the packing 12 to flow
through the slab 15. The slab is disposed in a wind flow 18 that
has a non-zero incident angle with one of the opposed dominant
faces 14. Similar to the gas-liquid contactor and the above
described method, the results from FIGS. 6-8 confirm that this
method may be applied to any gas-liquid contactor. It should be
understood that this gas-liquid contactor may have all of the same
characteristics as the carbon dioxide capture facility and
contactor disclosed herein.
[0076] Referring to FIG. 1, a gas-liquid contactor (illustrated by
facility 10) is also disclosed, comprising a slab 15 structure
comprising packing 12 and a liquid source 16 oriented to direct the
liquid into the packing 12 to flow in a mean liquid flow direction
20. The slab structure is disposed in a wind flow 18 that flows
obliquely or perpendicularly to the mean liquid flow direction 20.
Similar to the gas-liquid contactor and the above described
methods, the results from FIGS. 6-8 confirm that this method may be
applied to any gas-liquid contactor. It should be understood that
this gas-liquid contactor may have all of the same characteristics
as the carbon dioxide capture facility and contactor disclosed
herein.
[0077] Referring to FIG. 1, a method of contacting a liquid with a
moving gas (illustrated as wind flow 18) is disclosed. The method
comprises flowing the liquid through packing 12, and driving the
moving gas through the packing 12 in a drive direction (illustrated
as 18B, which is the same as wind direction 18 in this embodiment)
that is at least partially oriented with an ambient flow direction
18 of the moving gas. In the embodiment shown, the flowing gas is
wind, and the ambient flow direction is the ambient wind direction
18. This method may further comprise reversing the drive direction
18B when the ambient flow direction 18 reverses. Reversing the fan
direction (or more generally, reversing the forced flow of air
through the packing) in such a way as to drive the air with a
vector direction that is at least partially oriented with the
ambient wind 18 reduces the required fan power. Further, this
reduces the amount of low-CO.sub.2 air that is recycled back into
the inlet of the system, thus improving its efficiency. It is thus
advantageous to align the packing such that one of opposed dominant
face 14 is roughly perpendicular to the prevailing wind, in order
to maximize the efficiency of the fans.
[0078] In this document, wind flow is understood as moving gas
containing CO.sub.2.
Generating Carbon Credits
[0079] The carbon that is sequestered from a gas comprising carbon
dioxide using the methods described herein can be equated with, for
example, an environmental credit such as a carbon credit. Carbon
credits are used to provide an incentive to reduce greenhouse gas
emissions by capping total annual emissions and letting the market
assign a monetary value to a tradable unit. As used herein, carbon
credits include carbon credits as defined by provisions in place at
the time of filing but are not limited to such. Carbon credits also
refer to any type of tangible or intangible currency, stocks,
bonds, notes or other tradable or marketable unit used to value an
amount of carbon sequestered, an amount of greenhouse gas emissions
reduced, or any other type of carbon-neutral or carbon-negative
activities. A similar concept of environmental credits can be
applied, for example, for the implementation of best practices
related to environmental land practices.
[0080] Carbon credits can be obtained, for example, by applying and
receiving certification for the amount of carbon emissions reduced
(e.g., the amount of carbon sequestered, the amount of CO2 and
other greenhouse gases not released into the atmosphere). The
quality of the credits can be based in part on validation processes
and the sophistication of funds or development companies that act
as sponsors to carbon projects. See, for example, U.S. Patent
Publication Nos. 2002/0173979 and 2007/0073604 for representative
methods for verifying and valuing carbon credits. Carbon credits
can be exchanged between businesses or bought and sold in national
or international markets at a prevailing market price. In addition,
companies can sell carbon credits to commercial and individual
customers who are interested in voluntarily offsetting their carbon
footprints. These companies may, for example, purchase the credits
from an investment fund or a carbon development company that has
aggregated the credits from individual projects.
[0081] The process of applying for, obtaining and/or validating one
or more carbon credits may or may not include taking actual
measurements. Simply by way of example, each transfer of carbon
credits within Europe is validated by the ETS, and each
international transfer is validated by the United Nations Framework
Convention on Climate Change (UNFCCC).
[0082] In the claims, the word "comprising" is used in its
inclusive sense and does not exclude other elements being present.
The indefinite article "a" before a claim feature does not exclude
more than one of the feature being present. Each one of the
individual features described here may be used in one or more
embodiments and is not, by virtue only of being described here, to
be construed as essential to all embodiments as defined by the
claims.
* * * * *