U.S. patent application number 17/094871 was filed with the patent office on 2021-03-04 for production of calcium carbonate via solid-state calcium hydroxide particles and carbon dioxide, and associated systems and methods.
The applicant listed for this patent is Graymont (PA) Inc.. Invention is credited to Brent LaMar, Jared Ira Leikam, Joseph Lewis.
Application Number | 20210061668 17/094871 |
Document ID | / |
Family ID | 1000005210303 |
Filed Date | 2021-03-04 |
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United States Patent
Application |
20210061668 |
Kind Code |
A1 |
LaMar; Brent ; et
al. |
March 4, 2021 |
PRODUCTION OF CALCIUM CARBONATE VIA SOLID-STATE CALCIUM HYDROXIDE
PARTICLES AND CARBON DIOXIDE, AND ASSOCIATED SYSTEMS AND
METHODS
Abstract
Methods and systems for producing calcium carbonate from calcium
hydroxide and carbon dioxide are disclosed herein. In some
embodiments, a method for producing calcium carbonate comprises (i)
providing a first plurality of particles comprising solid-state
calcium hydroxide, and (ii) introducing a gas stream comprising
carbon dioxide to the first plurality of particles to produce a
second plurality of particles comprising calcium carbonate.
Individual ones of the first plurality of particles can include a
specific surface area of at least 20 m.sup.2/g and a free moisture
content of from 2% to 20%. The second plurality of particles
comprising calcium carbonate are not produced via
precipitation.
Inventors: |
LaMar; Brent; (Seattle,
WA) ; Leikam; Jared Ira; (West Jordan, UT) ;
Lewis; Joseph; (Stansbury Park, UT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Graymont (PA) Inc. |
Pleasant Gap |
PA |
US |
|
|
Family ID: |
1000005210303 |
Appl. No.: |
17/094871 |
Filed: |
November 11, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16572896 |
Sep 17, 2019 |
10870585 |
|
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17094871 |
|
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62732427 |
Sep 17, 2018 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C01F 11/18 20130101 |
International
Class: |
C01F 11/18 20060101
C01F011/18 |
Claims
1-11. (canceled)
12. A system for producing calcium carbonate, comprising: a
hydrator configured to add water to a first plurality of particles
comprising calcium oxide to produce a second plurality of particles
comprising solid-state calcium hydroxide particles, individual ones
of the calcium hydroxide particles including (i) a specific surface
area of at least 20 m.sup.2/g and (ii) a free moisture content of
from 2% to 20%; and a conditioner downstream of the hydrator and
positioned to receive the second plurality of particles and a gas
stream comprising carbon dioxide, the conditioner being configured
to produce a third plurality of particles comprising solid-state
calcium carbonate from the received second plurality of particles
and gas stream.
13. The system of claim 12, further comprising a grinder downstream
of the conditioner and positioned to receive the third plurality of
particles, the grinder being configured to reduce the particle size
of the third plurality of particles and thereby produce a fourth
plurality of particles.
14. The system of claim 13, wherein the conditioner is a first
conditioner and the gas stream is a first gas stream, the method
further comprising: a second conditioner downstream of the grinder
and positioned to receive the third plurality of particles and a
second gas stream comprising carbon dioxide, the second conditioner
being configured to produce a fourth plurality of particles
comprising calcium carbonate from the received third plurality of
particles and second gas stream.
15. The system of claim 12, wherein the third plurality of
particles comprising calcium carbonate particles not produced via
precipitation.
16. (canceled)
17. (canceled)
18. The system of claim 12, wherein individual ones of the second
plurality of particles comprise at least one of: a pore volume
greater than or equal to about 0.15 cm.sup.3/g; an average pore
diameter greater than or equal to about 200 Angstroms; a surface
area greater than or equal to 25 m.sup.2/g; or a free moisture
content of at least about 10%.
19. The system of claim 12, wherein the third plurality of
particles has a TAPPI brightness greater than or equal to 95.
20. The system of claim 12, wherein the second plurality of
particles is exposed to the gas stream in the conditioner for a
period of time of at least 15 minutes.
21. A system for producing calcium carbonate, comprising: a
hydrator configured to add water to a first plurality of particles
comprising calcium oxide to produce a second plurality of particles
comprising solid-state calcium hydroxide particles, individual ones
of the calcium hydroxide particles including a specific surface
area of at least 20 m.sup.2/g; and a conditioner downstream of the
hydrator and positioned to receive the second plurality of
particles and a gas stream comprising carbon dioxide, such that the
gas stream directly contacts the second plurality of particles to
produce a third plurality of particles comprising solid-state
calcium carbonate.
22. The system of claim 21, wherein the gas stream comprises at
least 30% by weight carbon dioxide.
23. The system of claim 21, wherein the third plurality of
particles comprises at least 40% by weight solid-state calcium
carbonate.
24. The system of claim 21, further comprising a grinder downstream
of the conditioner and positioned to receive the third plurality of
particles, the grinder being configured to reduce the particle size
of the third plurality of particles and thereby produce a fourth
plurality of particles.
25. The system of claim 24, wherein the conditioner is a first
conditioner and the gas stream is a first gas stream, the method
further comprising: a second conditioner downstream of the grinder
and positioned to receive the third plurality of particles and a
second gas stream comprising carbon dioxide, the second conditioner
being configured to produce a fourth plurality of particles
comprising calcium carbonate from the received third plurality of
particles and second gas stream.
26. The system of claim 21, wherein the third plurality of
particles comprising calcium carbonate particles are not produced
via precipitation.
27. The system of claim 21, wherein the third plurality of
particles is not part of a liquid slurry comprising precipitated
calcium carbonate.
28. The system of claim 21, wherein the second plurality of
particles comprise a specific surface area of at least 30
m.sup.2/g.
29. The system of claim 21, wherein the gas stream is provided via
a lime kiln.
30. The system of claim 21, wherein individual ones of the second
plurality of particles have a free moisture content of from 2% to
20% by weight.
31. The system of claim 21, wherein the third plurality of
particles has a TAPPI brightness greater than or equal to 95.
32. The system of claim 21, wherein the second plurality of
particles is part of a slurry comprising no more than 20% liquid by
weight.
33. The system of claim 21, wherein the second plurality of
particles is part of a slurry comprising at least 80% solids
content by weight.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] The present application is a divisional of U.S. patent
application Ser. No. 16/572,896, filed Sep. 17, 2019, which claims
the benefit of priority to U.S. Provisional Patent Application No.
62/732,427, filed Sep. 17, 2018, which is incorporated herein by
reference in its entirety.
TECHNICAL FIELD
[0002] The present disclosure relates generally to the production
of calcium carbonate via solid-state calcium hydroxide particles
and carbon dioxide, and associated systems and methods.
BACKGROUND
[0003] Calcium carbonate is used extensively in the papermaking and
paint industries, and for manufacturing of plastic materials,
sealing compounds, printing inks, rubbers and cosmetics, amongst
other applications. In these industries, the calcium carbonate is
often used as a filler component or coating pigment to increase
brightness characteristics of the material or product the calcium
carbonate is embedded in. Calcium carbonate has conventionally been
produced via precipitation, for example, by introducing carbon
dioxide into a lime slurry, sometimes referred to as the "milk of
lime." Carbonation of the milk produces an aqueous solution made up
of water and precipitated calcium carbonate (PCC). Once produced,
the aqueous solution is then dried to extract the PCC, which makes
up about 30% of the aqueous solution.
[0004] One drawback of the above-described, conventional method of
producing calcium carbonate is the time and expense associated with
drying the aqueous solution to extract the PCC. Because the calcium
carbonate makes up only about 30% of the aqueous solution,
significant energy is needed to dry the aqueous solution and
extract the calcium carbonate formed via precipitation.
Furthermore, facility equipment and personnel needed to perform the
operation of creating and drying the PCC solution result in
additional time, cost and resources. Accordingly, there exists a
need for improved systems and methods for producing calcium
carbonate particles.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] Many aspects of the present disclosure can be better
understood with reference to the following figures. The components
in the figures are schematic and thus are not to scale. Instead,
emphasis is placed on illustrating clearly the principles of the
present disclosure.
[0006] FIG. 1 is a schematic block diagram of a system for
producing calcium carbonate, in accordance with embodiments of the
present disclosure.
[0007] FIG. 2 is a flow diagram of a method for producing calcium
carbonate, in accordance with embodiments of the present
disclosure.
DETAILED DESCRIPTION
I. Overview
[0008] The present disclosure described herein relates to
improvements over conventional methods of producing calcium
carbonate. As previously described, these conventional methods
produce calcium carbonate via precipitation by forming an aqueous
solution or slurry that contains precipitated calcium carbonate
(PCC). This aqueous solution must be dried to isolate the PCC from
the rest of the solution before conducting further processing
(e.g., grinding) to produce a calcium carbonate product. Such
production methods are inefficient due to the energy needed to dry
the aqueous solution, and can create issues relating to inadequate
brightness characteristics of the extracted calcium carbonate, as
described elsewhere herein.
[0009] Embodiments of the present disclosure address at least some
of the issues associated with the conventional methods of producing
calcium carbonate. As described in additional detail below,
embodiments of the present disclosure produce calcium carbonate via
methods other than precipitating calcium carbonate via a liquid
slurry or aqueous solution. For example, in some embodiments a
first plurality of particles comprising solid-state calcium
hydroxide (e.g., enhanced hydrated lime) is provided, and a gas
stream comprising carbon dioxide is introduced to directly contact
the calcium hydroxide and produce solid-state particles comprising
calcium carbonate. The solid-state calcium hydroxide used to
produce the calcium carbonate particles can have particular
characteristics to aid conversion of calcium hydroxide to calcium
carbonate. As described in detail elsewhere herein, the calcium
hydroxide particles can have a specific surface area of at least
about 20 m.sup.2/g, a free moisture content of from about 2% to
20%, a pore volume of at least about 0.1 cm.sup.3/g, and/or an
average pore size diameter of at least about 100 angstroms. In some
embodiments, the produced particles can then be milled, dried, and
further exposed to additional gas streams comprising carbon dioxide
(e.g., iteratively milled, dried and exposed to carbon dioxide),
e.g., until a desired composition and/or conversion of calcium
carbonate is achieved. The produced calcium carbonate can have a
Technical Association of Pulp and Paper Industry (TAPPI) brightness
at or above a predetermined threshold (e.g., 80, 85, 90, 91. 92,
93, 94, 95, 96, 97, 98, or 99).
[0010] It will be readily understood that the embodiments of the
present disclosure described herein are exemplary. The following
detailed description of various embodiments is not intended to
limit the scope of the present disclosure, but is merely
representative of various embodiments. It will be appreciated that
various features are sometimes grouped together in a single
embodiment or description thereof for the purpose of streamlining
the disclosure. Many of these features may be used alone and/or in
combination with one another. Moreover, the order of the steps or
actions of the methods disclosed herein may be changed by those
skilled in the art without departing from the scope of the present
disclosure. In other words, unless a specific order of steps or
actions is required for proper operation of the embodiments, the
order or use of specific steps or actions may be modified.
Furthermore, sub-routines or only a portion of a method described
herein may be a separate method within the scope of this
disclosure. Stated otherwise, some methods may include only a
portion of the steps described in a more detailed method.
[0011] Many of the details and other features shown in the Figures
are merely illustrative of particular embodiments of the disclosed
technology. Accordingly, other embodiments can have other details
and features without departing from the spirit or scope of the
disclosure. In addition, those of ordinary skill in the art will
appreciate that further embodiments of the various disclosed
technologies can be practiced without several of the details
described below.
II. Production of Calcium Carbonate via Solid-State Calcium
Hydroxide Particles and Carbon Dioxide
[0012] FIG. 1 is a schematic block diagram of a system 100 for
producing calcium carbonate (CaCO.sub.3), in accordance with
embodiments of the present disclosure. As shown in FIG. 1, the
system 100 can include a hydrator 102 configured or positioned to
receive a first plurality of particles 101 comprising quicklime
(e.g., calcium oxide (CaO)), and produce a second plurality of
particles 103 comprising hydrated lime (e.g., calcium hydroxide
(Ca(OH).sub.2). The second plurality of particles 103 can include
at least about 90% or 95% by weight calcium hydroxide. The second
plurality of particles 103 can include particles that have not been
dried. In some embodiments, the hydrator 102 can include a feeder
configured to receive the first plurality of particles 101, and a
slaker or other hydration device configured to combine water with
the first plurality of particles 101, e.g., to convert calcium
oxide of the first plurality of particles 101 into a water
suspension or slurry of calcium hydroxide. As discussed elsewhere
herein, in some embodiments the feeder can control the feed rate of
particles to the slaker, such that the moisture content of the
produced calcium hydroxide of the second plurality of particles 103
is at or above a predetermined threshold. In some embodiments,
water is added to the quicklime of the first plurality of particles
101 such that the calcium hydroxide particles of the second
plurality of particles 103 have a residual or free moisture content
of at least about 1%, 2%, 3%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%,
13%, 14% 15%, 16%, 17%, 18%, 19%, 20%, or any value or range of
values between 1% and 20% by weight.
[0013] In some embodiments, the quicklime of the first plurality of
particles 101 may be slaked via the hydrator in the presence of one
or more additives (e.g., ethylene glycol, diethylene glycol,
triethylene glycol, monoethanolamine, diethanolamine,
triethanolamine, sodium or calcium lignosulfonate, and/or
combinations thereof). Without being bound by theory, using one or
more of these additives may inhibit "clumping" or the formation of
relatively large calcium hydroxide aggregates. Stated differently,
the additive(s) may result in an improved particle size
distribution of the second plurality of particles 103. Additionally
or alternatively, the additive(s) can also be added to the second
plurality of particles 103 (e.g., downstream of the hydrator 102),
e.g., to help negate a charge associated with the calcium hydroxide
particles. The additive(s) may also be incorporated into the system
100 at other stages of manufacturing (e.g., before, during, and/or
after milling). In some embodiments, the additive(s) are present in
the quicklime/water mixture within the hydrator 102 at a
concentration of from about 0.1% and 1.5% by weight of added water.
In some embodiments, no additive is used.
[0014] As described elsewhere herein, calcium carbonate is
conventionally produced via precipitation by injecting carbon
dioxide into a liquid lime slurry to form PCC. The aqueous or
liquid characteristics of the slurry contribute to a relatively
high conversion rate of the calcium hydroxide and production of
calcium carbonate. Some embodiments of the present disclosure do
not produce calcium carbonate via precipitation by injecting carbon
dioxide into a liquid lime slurry, but rather expose carbon dioxide
to calcium hydroxide particles in a solid-state. The solid-state
characteristics of the calcium hydroxide particles, relative to the
aqueous PCC solution, naturally result in less exposure time
between the carbon dioxide and the individual calcium hydroxide
particles. To increase exposure of the calcium hydroxide particles
to the carbon dioxide, the system 100 of the present technology
utilizes calcium hydroxide particles with contact-enhancing
characteristics, e.g., relative to more traditional lime hydrate
particles. As explained elsewhere herein, the individual calcium
hydroxide particles of the second plurality of particles 103 can
have certain characteristics, such as specific surface area,
moisture content (e.g., a free moisture content), porosity (e.g.,
pore size and/or pore volume), particle size, particle size
distribution, carbon dioxide content, and/or combinations thereof,
that are configured to increase the interactions between the carbon
dioxide molecules and calcium hydroxide particles. For example, in
some embodiments individual ones of the second plurality of
particles 103 can include a specific surface area of at least 15
m.sup.2/g, 20 m.sup.2/g, 25 m.sup.2/g, 30 m.sup.2/g, 35 m.sup.2/g,
40 m.sup.2/g, 45 m.sup.2/g, 50 m.sup.2/g, or any value or range of
values between 15 m.sup.2/g and 50 m.sup.2/g. The specific surface
area can be measured by equipment that uses gas sorption techniques
described in "Adsorption of Gases in Multimolecular Layers" by
Braunauer, Emmett, and Teller. Additionally or alternatively,
individual ones of the second plurality of particles 103 can
include a moisture content of no greater than about 20%, 19%, 18%,
17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%,
2%, or 1%, or any value or range of values between 1% and 20%.
Additionally or alternatively, individual ones of the second
plurality of particles 103 can include a pore volume of at least
about 0.1 cm.sup.3/g, 0.15 cm.sup.3/g, 0.2 cm.sup.3/g, 0.25
cm.sup.3/g, 0.3 cm.sup.3/g, 0.35 cm.sup.3/g, 0.4 cm.sup.3/g, or any
value or range of values between 0.1 cm.sup.3/g and 0.4 cm.sup.3/g.
Additionally or alternatively, individual ones of the second
plurality of particles 103 can include pores having openings of at
least about 100 angstroms, 150 angstroms, 200 angstroms, 250
angstroms, 300 angstroms, 350 angstroms, 400 angstroms, of any
value or range of values between 100 angstroms and 400 angstroms.
Additionally or alternatively, individual ones of the second
plurality of particles 103 can include a carbon dioxide content by
weight of less than about 4%, 3%, 2%, 1%, or any value or range of
values between 1% and 4%. Each of these characteristics may
contribute to an increased production and/or conversion of calcium
carbonate.
[0015] In some embodiments, the second plurality of particles 103
can include a particular particle size distribution. For example,
the ratio of the minimum diameter and maximum diameter of the
second plurality of particles can be greater than about 80%, 85%,
90%, 95%, or any value or range of values between 80% and 95%.
Additionally or alternatively, a D.sub.10 value of the second
plurality of particles can be (i) less than about 4.0 microns, or
(ii) within a range of from about 0.5 microns to 4.0 microns, or
any value or range of values between 0.5 microns and 4.0 microns.
Additionally or alternatively, a D.sub.90 value of the second
plurality of particles 103 can be (i) less than about 50 microns,
or (ii) within a range of from about 15 microns to 50 microns, or
any value or range of values between 15 microns and 50 microns.
Additionally or alternatively, the ratio of D.sub.90 to D.sub.10
(i.e., the "steepness") of the second plurality of particles 103
can be (i) no greater than 25, 20, 15, 10, or 8, or (ii) within a
range of from about 8 to 25, or any value or range of values
between 8 and 25. For purposes of this disclosure, the D.sub.X
value of a sample of particles is the diameter at which X % of the
sample is of particles having a diameter below the specified value.
For example, the D.sub.10 value of a sample of particles is the
diameter at which 10% of the sample's volume is from particles that
have a diameter that is less than the D.sub.10 value. Similarly,
the D.sub.90 value of a sample of particles is the diameter at
which 90% of the sample's volume is from particles that have a
diameter that is less than the D.sub.90 value. Additional details
regarding the composition, characteristics, parameters, and other
features associated with the calcium hydroxide are described in
U.S. patent application Ser. No. 15/922,179, now U.S. Pat. No.
10,369,518, filed Mar. 15, 2018, the disclosure of which is
incorporated herein by reference in its entirety.
[0016] As described elsewhere herein, the composition and
characteristics of the calcium hydroxide of the second plurality of
particles 103 can enable greater production of calcium carbonate
relative to utilizing calcium hydroxide without these
characteristics (e.g., traditional lime hydrate). For example, the
specific surface area and/or pore volume of the individual calcium
hydroxide particles of embodiments of the present disclosure are
generally greater than those of traditional lime hydrate. As such,
the specific surface area and/or pore volume of individual calcium
hydroxide particles of embodiments of the present disclosure are
able to absorb more carbon dioxide, thereby aiding the production
of calcium carbonate. As another example, the larger pore size of
individual calcium hydroxide particles of embodiments of the
present disclosure also aids the production of calcium carbonate.
For example, without being bound by theory, the larger pore size
can allow the carbon dioxide molecules to travel at least partially
through the pores of the calcium hydroxide particles. This is in
contrast to conventional methods in which the carbon dioxide
molecules engulf entire calcium hydroxide particles, which may
result in a "shelled" effect and lower calcium carbonate production
rates.
[0017] As shown in FIG. 1, the system 100 can further include a
conditioner 104 configured or positioned to (i) receive the second
plurality of particles 103, and a fluid 115a (e.g., a gas stream)
comprising carbon dioxide, and (ii) produce a third plurality of
particles 105 comprising calcium carbonate via Reaction 1.
Ca(OH).sub.2(s)+CO.sub.2(g).fwdarw.CaCO.sub.3(s)+H.sub.2O(l)
(Reaction 1)
[0018] The fluid 115a can be injected into the conditioner 104 such
that the carbon dioxide of the fluid 115a directly contacts at
least a portion of the second plurality of particles 103. The fluid
115a can include off-gas from a combustion process or be at least
partially sourced from an off-gas stream. For example, the fluid
115a may be sourced from a combustion process associated with a
lime kiln. Additionally or alternatively, the fluid 115a can be at
least partially sourced from a pure carbon dioxide source (e.g., a
liquid carbon dioxide tank). In such embodiments, the pure carbon
dioxide source may be blended with the off-gas. The carbon dioxide
composition of the fluid 115a can be at or above a predetermined
threshold (e.g., about 30%, 40%, 50%, 60%, 65%, 70%, 75%, 80%, 85%,
90%, 95%, 98%, 99%, or any value or range of values between 30% and
99%).
[0019] The conditioner 104 can include a pressure vessel or
container having one or more injection or input points for
receiving the fluid 115a and exposing it to the second plurality of
particles 103. In some embodiments, the conditioner 104 is
configured to withstand pressures of at least about 50 kilopascals
(kPa), 100 kPa, 200 kPa, 400 kPa, 500 kPa, 750 kPa, 1 megapascal
(MPa), 2 MPa, 3 MPa, or any value or range of values between 50 kPa
and 3 MPa. Without being bound by theory, a relatively higher
pressure can increase the production and/or conversion percentage
of calcium carbonate by increasing exposure of the calcium
hydroxide, carbon dioxide, and/or water compounds to one another.
For example, a relatively higher pressure can enable the carbon
dioxide to further penetrate the calcium hydroxide and/or maintain
water molecules in the liquid phase. Additionally or alternatively,
in some embodiments the conditioner 104 is configured to withstand
temperatures of at least about 50.degree. C., 60.degree. C.,
70.degree. C., or 80.degree. C., or any value or range of values
between 50.degree. C. and 80.degree. C. The conditioner 104 can
include one or more mixing areas, mixing devices, augers, and/or
paddles (e.g., rotating paddles configured to rotate in opposite
directions). The conditioner 104 can be configured to increase
exposure time, e.g., relative to in-line mixing, between the carbon
dioxide of the fluid 115a and individual calcium hydroxide
particles of the second plurality of particles 103, e.g., to
increase the production of calcium carbonate.
[0020] In some embodiments, the second plurality of particles 103
can be exposed to the carbon dioxide of the fluid 115a for a period
of time of at least about 5 minutes, 10 minutes, 15 minutes, 30
minutes, 60 minutes, or any value or range of values between 5
minutes and 60 minutes. Without being bound by theory, increasing
the exposure time of the calcium hydroxide to the carbon dioxide
can improve conversion percentage and/or production of calcium
carbonate. For purposes of this disclosure, "conversion" refers to
the percentage of calcium carbonate particles present in the
produced plurality of particles.
[0021] The third plurality of particles 105 can include a
combination of calcium carbonate particles and unreacted calcium
hydroxide particles. In some embodiments, the composition of the
third plurality of particles 105 can include at least about 40%,
50%, 60%, 70%, 80%, 90%, or any value or range of values between
40% and 90%, calcium carbonate by weight. Additionally or
alternatively, in some embodiments, the composition of the third
plurality of particles 105 can include less than 60%, 50%, 40%,
30%, 20%, 10%, or any value or range of values between 10% and 60%,
calcium hydroxide by weight.
[0022] As shown in FIG. 1, the system 100 can further include a
grinder 106 configured or positioned to (i) receive the third
plurality of particles 105, and a fluid 115b comprising carbon
dioxide, and (ii) produce a fourth plurality of particles 107
comprising calcium carbonate. The fluid 115b can be similar or
identical to the fluid 115a described elsewhere herein, and can be
sourced from the same or a different location than the fluid 115a.
The grinder 106 can include a mill (e.g., a grinding mill, an
impact mill, attritor cell mill, etc.) or other device(s)
configured to break particles into smaller particles via grinding
or crushing. Breaking the third plurality of particles 105 into
smaller particles can expose additional surface area of the third
plurality of particles 105, and thereby aid in calcium carbonate
production and/or conversion. The grinder 106 can be configured
such that the produced fourth plurality of particles 107 has one or
more desired characteristics (e.g., steepness, particle size
distribution, etc.). For example, the steepness of the fourth
plurality of particles 105 may directly correlate to time spent in
the grinder 106 (e.g., residence time) and may decrease as a result
of grinding, thereby creating a more uniform particle size. The
grinder 106 can include one or more air classification units, e.g.,
to increase exposure of the carbon dioxide from the fluid 115b to
individual calcium hydroxide particles of the third plurality of
particles 105 in the grinder 106. In some embodiments, carbon
dioxide is exposed to the third plurality of particles 105 as they
are being grinded via the grinder 106.
[0023] The fourth plurality of particles 107 can include a
combination of calcium carbonate particles and unreacted calcium
hydroxide particles. Generally speaking, the composition of the
fourth plurality of particles 107 can include a higher
concentration of calcium carbonate particles and a lower
concentration of calcium hydroxide particles than that of the third
plurality of particles 105. In some embodiments, the composition of
the fourth plurality of particles 107 can include at least about
60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99% or any value or range
of values between 60% and 99%, calcium carbonate by weight.
Additionally or alternatively, in some embodiments, the composition
of the fourth plurality of particles 105 can include less than 40%,
30%, 20%, 10%, or any value or range of values between 10% and 40%,
calcium hydroxide by weight.
[0024] As shown in FIG. 1, the system 100 can further include a
conditioner 108 configured or positioned to (i) receive the fourth
plurality of particles 107, and a fluid 115c comprising carbon
dioxide, and (ii) produce a fifth plurality of particles 109
comprising calcium carbonate. The fluid 115c can be similar or
identical to one or both of the fluids 115a, 115b described
elsewhere herein, and can be sourced from the same or a different
location than one or both of the fluids 115a, 115b. The conditioner
108 can include similar or identical features to the conditioner
104 described elsewhere herein. In some embodiments, the
conditioners 104, 108 may be a single unit. For example, in such
embodiments the single unit conditioner may have multiple stages
(e.g., first, second, third or more stages) in which the second
plurality of particles 103 is received by a first stage of the
conditioner and the fourth plurality of particles 107 is received
by a second stage of the conditioner.
[0025] The fifth plurality of particles 109 can include a
combination of calcium carbonate particles and, in some
embodiments, unreacted calcium hydroxide particles. Generally
speaking, the composition of the fifth plurality of particles 107
can include a higher concentration of calcium carbonate particles
and a lower concentration of calcium hydroxide particles than that
of the fourth plurality of particles 107. In some embodiments, the
composition of the fifth plurality of particles 109 can include at
least about 80%, 90%, 95%, 96%, 97%, 98%, 99% or any value or range
of values between 80% and 99%, calcium carbonate by weight.
Additionally or alternatively, in some embodiments, the composition
of the fifth plurality of particles 109 can include less than 10%
or 5% calcium hydroxide by weight.
[0026] As shown in FIG. 1, the system 100 can further include a
dryer 110 configured or positioned to receive the fifth plurality
of particles 109 and produce a sixth plurality of particles 111
comprising calcium carbonate. The dryer 110 can include a heater or
other device configured to reduce the moisture content of the fifth
plurality of particles 109 via direct or indirect heat. For
example, the fifth plurality of particles 109 may be indirectly
heated with a heated gas, such as atmospheric air, that has a
temperature of between about 150.degree. C. and 425.degree. C., or
any value or range of values between 150.degree. C. and about
425.degree. C. In some embodiments, the dryer 110 and grinder 106
can be a single unit such that grinding and drying of the particles
occurs simultaneously.
[0027] The sixth plurality of particles 111 (e.g., a product
stream) can include calcium carbonate. Generally speaking, the
composition of the sixth plurality of particles 111 can include a
higher concentration of calcium carbonate particles and/or a lower
concentration of calcium hydroxide particles than that of the fifth
plurality of particles 109. In some embodiments, the composition of
the sixth plurality of particles 111 can include at least about
90%, 95%, 96%, 97%, 98%, 99% or any value or range of values
between 90% and 99%, calcium carbonate by weight. Additionally or
alternatively, in some embodiments, the composition of the sixth
plurality of particles 111 can include less than 5% calcium
hydroxide by weight. In some embodiments, the produced calcium
carbonate of the sixth plurality of particles can include a TAPPI
brightness above a predetermined threshold (e.g., 80, 85, 90, 91.
92, 93, 94, 95, 96, 97, 98, or 99).
[0028] The sixth plurality of particles 111 can be provided to
other processes or systems for further downstream processing or
quality testing. For example, the sixth plurality of particles 111
may be sieved, filtered or otherwise modified (e.g., via an air
classifier or a cyclone) prior to being directed to a finished
product bin for distribution. In some embodiments, the particles
are sieved through a mesh having a pore size of about 600 microns,
300 microns, 150 microns, 75 microns, 45 microns, or 32 microns, or
any value or range of values between 32 microns and 600 microns. In
some embodiments, the sixth plurality of particles 111 are not
sieved.
[0029] In some embodiments, the sixth plurality of particles 111
may be measured, e.g., to determine conversion percentage, or a
percent composition of calcium carbonate and/or calcium hydroxide.
For example, depending on whether the conversion and/or composition
exceeds a predetermined threshold, the sixth plurality of particles
111 may be directed as product to shipping containers, or re-routed
(e.g., recycled) to for further processing (e.g., milling, drying,
and/or exposing calcium hydroxide to further carbon dioxide) to
increase conversion or composition of calcium carbonate.
[0030] As shown in FIG. 1, the system 100 can further include a
control system 120 to control operations associated with the system
100. Many embodiments of the control system 120 and/or technology
described below may take the form of computer-executable
instructions, including routines executed by a programmable
computer. The control system 120 may, for example, also include a
combination of supervisory control and data acquisition (SCADA)
systems, distributed control systems (DCS), programmable logic
controllers (PLC), control devices, and processors configured to
process computer-executable instructions. Those skilled in the
relevant art will appreciate that the technology can be practiced
on computer systems other than those described herein. The
technology can be embodied in a special-purpose computer or data
processor that is specifically programmed, configured or
constructed to perform one or more of the computer-executable
instructions described below. Accordingly, the term "control
system" as generally used herein refers to any data processor.
Information handled by the control system 120 can be presented at
any suitable display medium, including a CRT display or LCD.
[0031] The technology can also be practiced in distributed
environments, where tasks or modules are performed by remote
processing devices that are linked through a communications
network. In a distributed computing environment, program modules or
subroutines may be located in local and remote memory storage
devices. Aspects of the technology described below may be stored or
distributed on computer-readable media, including magnetic or
optically readable or removable computer disks, as well as
distributed electronically over networks. Data structures and
transmissions of data particular to aspects of the technology are
also encompassed within the scope of particular embodiments of the
disclosed technology.
[0032] The system 100 may be operated as a batch process or a
steady-state process. Additionally, the system 100 may include
other processes similar to those previously described that are
utilized in series or in parallel to the system 100 illustrated in
FIG. 1.
[0033] Embodiments of the present disclosure have multiple
advantages over conventional methods of producing calcium
carbonate. For example, one advantage of at least some embodiments
of the present disclosure is the ability to produce a brighter
calcium carbonate product that is not dependent, or less dependent,
on the raw stone material used to produce the calcium carbonate.
Generally, the brightness of calcium carbonate product is a
desirable characteristic, as it allows the calcium carbonate to be
used in more applications and allows manufacturers to obtain higher
profit margins. When using conventional methods to produce calcium
carbonate (e.g., by producing PCC), brightness characteristics are
largely based on the raw stone material that is used, with high
bright stone (e.g., lighter-colored) material resulting in a
calcium carbonate product with higher brightness, and low bright
stone (e.g., darker-colored) material resulting in a calcium
carbonate product with lower brightness. High bright stone is
sourced from fewer geographic locations around the world relative
to the available locations to source low bright stone. As such,
customers or applications that need higher brightness calcium
carbonate but who operate far away from these geographic locations
with high bright stone material, often need to pay higher
distribution costs for the brighter calcium carbonate product to be
shipped longer distances.
[0034] At least some embodiments of the present disclosure
alleviate this issue because they allow calcium carbonate product
to be produced from stone material that does not necessarily have
high brightness. Stated differently, embodiments of the present
disclosure can produce calcium carbonate particles having high
brightness characteristics from what are traditionally considered
to be the low bright stone (e.g., darker-colored) material. This
ability to produce higher brightness characteristics from low
bright stone is due in part to the enhanced hydrate particles that
are formed from calcium oxide particles, which are formed from the
raw stone material. The raw stone material undergoes a calcination
process whereby chemically-bound carbon dioxide of the raw stone
material is removed from the stone, thereby producing calcium oxide
having generally the same or enhanced brightness characteristics.
As the calcium oxide is then slaked to form the calcium hydroxide
particles, these brightness characteristics are maintained in the
calcium hydroxide particles, which are then exposed to carbon
dioxide to form the calcium carbonate product, as described
elsewhere herein. Through this process, the brightness
characteristics of the calcium oxide particles is at least
maintained or enhanced, thereby producing a calcium carbonate
product with greater brightness characteristics. As a result,
embodiments of the present disclosure are able to produce calcium
carbonate product having higher brightness characteristics in more
geographic locations and at lower costs, relative to conventional
methods.
[0035] Another advantage of at least some embodiments of the
present disclosure is the avoidance of creating a liquid slurry of
PCC, which can thereby reduce the time and expense associated with
having to first produce the liquid slurry and then dry the liquid
slurry to extract the precipitated calcium carbonate. As described
elsewhere herein, the present disclosure instead produces calcium
carbonate via methods other than precipitation, for example by
exposing carbon dioxide to solid-state calcium hydroxide particles
having improved characteristics (e.g., specific surfaces areas,
moisture content, pore volumes, pore diameters, etc.) relative to
conventional lime hydrate particles.
[0036] Yet another advantage of at least some embodiments of the
present disclosure is the ability to reduce the amount of carbon
dioxide released to the atmosphere. Lime kiln, cement, power and
other industrial facilities use combustion firing to heat their
process gas and/or other streams, and as a result generate
combustion off-gas streams having substantial amounts of carbon
dioxide. In at least some of these industrial processes, these gas
streams comprising carbon dioxide are vented to the atmosphere
which can result in an expense for the facility, since carbon
dioxide is considered a green-house gas and is regulated by local
and national agencies. Embodiments of the present disclosure enable
these facilities to utilize at least a portion of these off-gas
streams in a way that can produce additional revenue.
[0037] FIG. 2 is a flow diagram of a method 200 for producing
calcium carbonate, in accordance with embodiments of the present
disclosure. The method 200 includes slaking a first plurality of
particles (e.g., the first plurality of particles 101; FIG. 1)
comprising calcium oxide to produce a second plurality of particles
(e.g., the second plurality of particles 103; FIG. 1) comprising
calcium hydroxide (process portion 202). In some embodiments, the
slaking is performed via a hydrator (e.g., the hydrator 102; FIG.
1). The second plurality of particles are particles in a
solid-state that are either not contained in a slurry or aqueous
solution, or are contained in a slurry having (i) less than 30%
water or moisture (e.g., less than 25%, 20%, 15%, 10%, or any value
or range of values between 10% and 30% water or moisture) or (ii)
more than 70% solids content by weight (e.g., more than 75%, 80%,
85%, 90%, 95%, or any value or range of values between 70% to
95%).
[0038] The method 200 further includes introducing a first gas
stream (e.g., the fluid 115a; FIG. 1) comprising carbon dioxide to
the second plurality of particles to produce a third plurality of
particles (e.g., the third plurality of particles 105; FIG. 1)
comprising calcium carbonate (process portion 204). Introducing the
first gas stream can include injecting the first gas stream into a
conditioner (e.g., the conditioner 104) or other mixing area
containing the second plurality of particles, such that the carbon
dioxide of the first gas stream directly contacts the solid-state
calcium hydroxide particles of the second plurality of particles.
When the first gas stream is introduced, the second plurality of
particles are either not contained in a slurry, or are contained in
a slurry having (i) less than 30% water or moisture (e.g., less
than 25%, 20%, 15%, 10%, or any value or range of values between
10% and 30% water or moisture) or (ii) more than 70% solids content
by weight (e.g., more than 75%, 80%, 85%, 90%, 95%, or any value or
range of values between 70% to 95%).
[0039] The method 200 further includes grinding at least a portion
of the third plurality of particles (process portion 206). Grinding
the third plurality of particles can occur in a grinder (e.g., the
grinder 106; FIG. 1), and can break the third plurality of
particles into smaller particles and expose additional surface area
of the particles to carbon dioxide. In doing so, the conversion or
production of calcium carbonate can be increased.
[0040] The method 200 further includes introducing a second gas
stream (e.g., the fluid 115b or 115c) comprising carbon dioxide to
the milled third plurality of particles (e.g., the fourth plurality
of particles 107; FIG. 1) to produce product particles (e.g., the
fifth plurality of particles 109 or the sixth plurality of
particles 111; FIG. 1) comprising calcium carbonate (process
portion 208). In some embodiments, the composition of the product
particles can include at least about 90%, 95%, 96%, 97%, 98%, 99%
or any value or range of values between 90% and 99%, calcium
carbonate by weight. Additionally or alternatively, the produced
calcium carbonate of the sixth plurality of particles can include a
TAPPI brightness of 80, 85, 90, 91. 92, 93, 94, 95, 96, 97, 98, or
99, or a value or range of values between 80 and 99.
CONCLUSION
[0041] It will be apparent to those having skill in the art that
changes may be made to the details of the above-described
embodiments without departing from the underlying principles of the
present disclosure. In some cases, well known structures and
functions have not been shown or described in detail to avoid
unnecessarily obscuring the description of the embodiments of the
present technology. Although steps of methods may be presented
herein in a particular order, alternative embodiments may perform
the steps in a different order. Similarly, certain aspects of the
present technology disclosed in the context of particular
embodiments can be combined or eliminated in other embodiments.
Furthermore, while advantages associated with certain embodiments
of the present technology may have been disclosed in the context of
those embodiments, other embodiments can also exhibit such
advantages, and not all embodiments need necessarily exhibit such
advantages or other advantages disclosed herein to fall within the
scope of the technology. Accordingly, the disclosure and associated
technology can encompass other embodiments not expressly shown or
described herein, and the invention is not limited except as by the
appended claims.
[0042] Throughout this disclosure, the singular terms "a," "an,"
and "the" include plural referents unless the context clearly
indicates otherwise. Similarly, unless the word "or" is expressly
limited to mean only a single item exclusive from the other items
in reference to a list of two or more items, then the use of "or"
in such a list is to be interpreted as including (a) any single
item in the list, (b) all of the items in the list, or (c) any
combination of the items in the list. Additionally, the term
"comprising," "including," and "having" should be interpreted to
mean including at least the recited feature(s) such that any
greater number of the same feature and/or additional types of other
features are not precluded.
[0043] Reference herein to "one embodiment," "an embodiment," "some
embodiments" or similar formulations means that a particular
feature, structure, operation, or characteristic described in
connection with the embodiment can be included in at least one
embodiment of the present technology. Thus, the appearances of such
phrases or formulations herein are not necessarily all referring to
the same embodiment. Furthermore, various particular features,
structures, operations, or characteristics may be combined in any
suitable manner in one or more embodiments.
[0044] Unless otherwise indicated, all numbers expressing
concentrations, compositions, specific surface areas, pore sizes,
pore volumes, moisture content, and other numerical values used in
the specification and claims, are to be understood as being
modified in all instances by the term "about." Accordingly, unless
indicated to the contrary, the numerical parameters set forth in
the following specification and attached claims are approximations
that may vary depending upon the desired properties sought to be
obtained by the present technology. At the very least, and not as
an attempt to limit the application of the doctrine of equivalents
to the scope of the claims, each numerical parameter should at
least be construed in light of the number of reported significant
digits and by applying ordinary rounding techniques. Additionally,
all ranges disclosed herein are to be understood to encompass any
and all subranges subsumed therein. For example, a range of "1 to
10" includes any and all subranges between (and including) the
minimum value of 1 and the maximum value of 10, i.e., any and all
subranges having a minimum value of equal to or greater than 1 and
a maximum value of equal to or less than 10, e.g., 5.5 to 10.
[0045] The disclosure set forth above is not to be interpreted as
reflecting an intention that any claim requires more features than
those expressly recited in that claim. Rather, as the following
claims reflect, inventive aspects lie in a combination of fewer
than all features of any single foregoing disclosed embodiment.
Thus, the claims following this Detailed Description are hereby
expressly incorporated into this Detailed Description, with each
claim standing on its own as a separate embodiment. This disclosure
includes all permutations of the independent claims with their
dependent claims.
[0046] The present technology is illustrated, for example,
according to various aspects described below. Various examples of
aspects of the present technology are described as numbered clauses
(1, 2, 3, etc.) for convenience. These clauses are provided as
examples and do not limit the present technology. It is noted that
any of the dependent clauses may be combined in any combination,
and placed into a respective independent clause. The other clauses
can be presented in a similar manner.
[0047] Clause 1: A method for producing calcium carbonate from
calcium hydroxide and carbon dioxide, comprising: providing a first
plurality of particles comprising solid-state calcium hydroxide;
and introducing a gas stream comprising carbon dioxide to the first
plurality of particles to produce a second plurality of particles
comprising solid-state calcium carbonate.
[0048] Clause 2: The method of clause 1, wherein the first and
second pluralities of particles are not part of a liquid slurry or
aqueous solution comprising precipitated calcium carbonate.
[0049] Clause 3: The method of any one of the previous clauses,
wherein providing the first plurality of particles comprises
providing a slurry including the first plurality of particles, the
slurry including no more than 20% liquid.
[0050] Clause 4: The method of any one of the previous clauses,
wherein providing the first plurality of particles comprises
providing a slurry including the first plurality of particles, the
slurry including at least 80% solids content by weight.
[0051] Clause 5: The method of any one of the previous clauses,
wherein the second plurality of particles comprising calcium
carbonate is not produced via precipitation.
[0052] Clause 6: The method of any one of the previous clauses,
wherein the second plurality of particles comprises at least 95%
calcium carbonate.
[0053] Clause 7: The method of any one of the previous clauses,
wherein: the first plurality of particles comprises at least 90%
calcium hydroxide, providing the first plurality of particles
comprises providing the first plurality of particles to a
conditioner, and introducing the gas stream includes injecting the
gas stream to the conditioner, thereby causing the carbon dioxide
of the gas stream to directly contact the first plurality of
particles.
[0054] Clause 8: The method of clause 7, further comprising
exposing the gas stream to the first plurality of particles in the
conditioner for a predetermined period of time of at least 10
minutes.
[0055] Clause 9: The method of any one of the previous clauses,
wherein providing the first plurality of particles comprises
slaking calcium oxide to produce the first plurality of particles,
the method further comprising: after introducing the gas stream,
milling at least a portion of the second plurality of particles;
and after milling, drying at least a portion of the milled second
plurality of particles.
[0056] Clause 10: The method of clause 9, wherein slaking comprises
slaking the calcium oxide in the presence of at least one of
glycol, diethylene glycol, triethylene glycol, monoethanolamine,
diethanolamine, triethanolamine, sodium, or calcium
lignosulfonate.
[0057] Clause 11: The method of any one of clauses 9 or 10, further
comprising, prior to introducing the gas stream, filtering the
first plurality of particles such that the filtered first plurality
of particles has a D.sub.90/D.sub.10 ratio less than 6.
[0058] Clause 12: The method of any one of the previous clauses,
wherein the gas stream is a first gas stream, the method further
comprising: after introducing the first gas stream, grinding at
least a portion of the second plurality of particles to produce a
third plurality of particles comprising a first concentration of
calcium carbonate; and after grinding, introducing a second gas
stream comprising carbon dioxide to the third plurality of
particles to produce a fourth plurality of particles comprising a
second concentration of calcium carbonate greater than the first
concentration of calcium carbonate.
[0059] Clause 13: The method of clause 12, further comprising,
while grinding, introducing a third gas stream comprising carbon
dioxide to the second plurality of particles.
[0060] Clause 14: The method of any one of the previous clauses,
wherein the gas stream comprising carbon dioxide is (a) an off-gas
stream, (b) a process gas stream, or (c) a combination of (a) and
(b).
[0061] Clause 15: The method of any one of the previous clauses,
wherein the carbon dioxide comprises at least about 40% of the gas
stream.
[0062] Clause 16: The method of any one of the previous clauses,
wherein the gas stream comprising carbon dioxide is received from a
lime kiln.
[0063] Clause 17: The method of any one of the previous clauses,
wherein individual ones of the first plurality of particles have a
pore volume greater than or equal to about 0.15 cm.sup.3/g.
[0064] Clause 18: The method of any one of the previous clauses,
wherein individual ones of the first plurality of particles have an
average pore diameter greater than or equal to about 200
Angstroms.
[0065] Clause 19: The method of any one of the previous clauses,
wherein individual ones of the first plurality of particles have a
surface area greater than or equal to 25 m.sup.2/g.
[0066] Clause 20: The method of any one of the previous clauses,
wherein individual ones of the first plurality of particles have a
free moisture content of at least about 10%.
[0067] Clause 21: The method of any one of the previous clauses,
wherein the first plurality of particles has an average D.sub.90 of
at least 3 microns.
[0068] Clause 22: The method of any one of the previous clauses,
wherein the second plurality of particles has an average brightness
greater than or equal to 90.
[0069] Clause 23: A system for producing calcium carbonate,
comprising: a hydrator configured to add water to a first plurality
of particles comprising calcium oxide to produce a second plurality
of particles comprising solid-state calcium hydroxide particles;
and a conditioner downstream of the hydrator and positioned to
receive the second plurality of particles and a gas stream
comprising carbon dioxide, the conditioner being configured to
produce a third plurality of particles comprising solid-state
calcium carbonate from the received second plurality of particles
and gas stream.
[0070] Clause 24: The system of clause 23, further comprising a
grinder downstream of the conditioner and positioned to receive the
third plurality of particles, the grinder being configured to
reduce the particle size of the third plurality of particles and
thereby produce a fourth plurality of particles.
[0071] Clause 25: The system of clause 24, wherein the conditioner
is a first conditioner and the gas stream is a first gas stream,
the method further comprising: a second conditioner downstream of
the grinder and positioned to receive the third plurality of
particles and a second gas stream comprising carbon dioxide, the
second conditioner being configured to produce a fourth plurality
of particles comprising calcium carbonate from the received third
plurality of particles and second gas stream.
[0072] Clause 26: The system of clause 25, further comprising a
dryer downstream of the second conditioner and positioned to
receive the fourth plurality of particles, the dryer being
configured to reduce a free moisture content of the fourth
plurality of particles.
[0073] Clause 27: The system of any one of the previous clauses,
further comprising a dryer downstream of the grinder and positioned
to receive the fourth plurality of particles, the dryer being
configured to reduce a free moisture content of the third plurality
of particles.
[0074] Clause 28: The system of any one of the previous clauses,
wherein the third plurality of particles comprising calcium
carbonate particles are not produced via precipitation.
[0075] Clause 29: The system of any one of the previous clauses,
wherein the second plurality of particles is part of a slurry
comprising no more than 20% liquid by weight.
[0076] Clause 30: The system of any one of the previous clauses,
wherein the second plurality of particles is part of a slurry
comprising at least 80% solids content by weight.
[0077] Clause 31: The system of any one of the previous clauses,
wherein individual ones of the second plurality of particles have a
pore volume greater than or equal to about 0.15 cm.sup.3/g.
[0078] Clause 32: The system of any one of the previous clauses,
wherein individual ones of the second plurality of particles have
an average pore diameter greater than or equal to about 200
Angstroms.
[0079] Clause 33: The system of any one of the previous clauses,
wherein individual ones of the second plurality of particles have a
surface area greater than or equal to 25 m.sup.2/g.
[0080] Clause 34: The system of any one of the previous clauses,
wherein individual ones of the second plurality of particles have a
free moisture content of at least about 10%.
[0081] Clause 35: The system of any one of the previous clauses,
wherein the second plurality of particles has an average D.sub.90
of at least 3 microns.
[0082] Clause 36: The system of any one of the previous clauses,
wherein the third plurality of particles has a brightness greater
than or equal to 95.
[0083] Clause 37: The system of any one of the previous clauses,
wherein the second plurality of particles is exposed to the gas
stream in the conditioner for a period of time of at least 15
minutes.
[0084] Clause 38: A method for producing calcium carbonate without
precipitation, comprising: slaking a first plurality of particles
to produce a second plurality of particles comprising calcium
hydroxide, wherein individual ones of the second plurality of
particles include a surface area of at least about 20 m.sup.2/g and
a moisture content of from about 2% to 20%; introducing a gas
stream comprising carbon dioxide to the second plurality of
particles to produce a third plurality of particles comprising
calcium carbonate and calcium hydroxide; and milling at least a
portion of the third plurality of particles to produce a fourth
plurality of particles.
[0085] Clause 39: The method of any one of the previous clauses,
wherein the gas stream is a first gas stream, the method further
comprising introducing a second gas stream comprising carbon
dioxide to the fourth plurality of particles to produce a fifth
plurality of particles comprising calcium carbonate, the fifth
plurality of particles having a higher concentration of calcium
carbonate than that of the fourth plurality of particles.
[0086] Clause 40: The method of any one of the previous clauses,
wherein the gas stream is a first gas stream, the method further
comprising introducing a second gas stream comprising carbon
dioxide to the third plurality of particles while the third
plurality of particles is being milled.
[0087] Clause 41: The method of any one of the previous clauses,
wherein the second plurality of particles comprise: an average pore
volume of at least about 0.15 cm.sup.3/g; an average pore diameter
of at least about 200 angstroms; and an average D.sub.90 no greater
than about 4 microns.
[0088] Clause 42: The method of any one of the previous clauses,
wherein the second plurality of particles comprise a steepness of
no greater than about 5.
* * * * *