Note: Descriptions are shown in the official language in which they were submitted.
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SYSTEM AND METHOD FOR MANUFACTURING CALCINED GYPSUM WITH
IN-LINE CALCINATION CONTROL DEVICE
[0001] This patent application claims the benefit of priority to
U.S. Provisional Patent
Application No. 63/245,798, filed September 17, 2021, and entitled, "System
and
Method for Manufacturing Calcined Gypsum with In-Line Calcination Control
Device,"
which is incorporated in its entirety herein by this reference.
BACKGROUND
[0002] The present disclosure relates to systems and methods for
calcining gypsum,
such as, e.g., is used in continuous cementitious board manufacturing
processes, and,
more particularly, to a system and method for calcining gypsum which includes
an in-
line calcination control device adapted to control at least one operating
parameter
based upon a signal received from an x-ray analyzer.
[0003] Calcium sulfate materials are available in several forms or
phases that are
simplified as follows: calcium sulfate dihydrate¨CaSO4.2H20 (commonly known as
gypsum); calcium sulfate hemihydrate¨CaSO4.1/2H20 (commonly known as stucco);
and calcium sulfate¨CaSO4 (commonly known as anhydrite). In many types of
cementitious articles, set gypsum (calcium sulfate dihydrate) is often a major
constituent. For example, set gypsum is a major component of end products
created by
use of traditional plasters (e.g., plaster-surfaced internal building walls),
and also in
faced gypsum board employed in typical drywall construction of interior walls
and
ceilings of buildings. In addition, set gypsum is the major component of
gypsum/cellulose fiber composite boards and products, as described in U.S.
Patent No.
5,320,677, for example. Typically, such gypsum-containing cementitious
products are
made by preparing a mixture of calcined gypsum (comprising calcium sulfate
hemihydrate alpha or beta and/or calcium sulfate anhydrite), water, and other
components, as appropriate to form cementitious slurry. The cementitious
slurry and
desired additives are often blended in a continuous mixer, as described in
U.S. Patent
No. 3,359,146, for example.
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[0004] The mixture typically is cast into a pre-determined shape or
onto the surface
of a substrate. The calcined gypsum reacts with the water to form a matrix of
crystalline
hydrated gypsum, i.e., calcium sulfate dihydrate. It is the desired hydration
of calcined
gypsum that enables the formation of an interlocking matrix of set gypsum,
thereby
imparting strength to the gypsum structure in the gypsum-containing product.
[0005] Calcined gypsum is typically made by crushing gypsum rock and
then heating
the gypsum at atmospheric pressure to calcine (dehydrate) the calcium sulfate
dihydrate into preferably calcium sulfate hemihydrate. In addition to natural
gypsum
rock, the use of synthetic gypsum, such as, e.g., flue gas desulphurization
gypsum or
gypsum from chemical processes can be used as well. The calcining of gypsum
typically occurs in a large atmospheric pressure kettle containing a mixture
of the
various phases of the gypsum.
[0006] When gypsum, (i.e., calcium sulfate dihydrate) is calcined,
water is removed
from the calcium sulfate molecular structure. When one and a half molecules of
water
are removed from the molecular structure of gypsum, the hemihydrate results, a
material used in various compositions in which rehydration occurs during the
setting
process subsequent to the addition of the water. When two molecules of water
are
removed from the molecular structure of gypsum, the anhydrite results.
Anhydrites
formed by calcining at low temperatures are able to rehydrate when exposed to
moist
conditions. However, if the calcium sulfate is calcined at high temperatures,
typically of
about 900 F or more, an insoluble form of calcium sulfate results.
[0007] For example, gypsum (CaSO4.2H20) powder, from sources such as
rocks of
natural gypsum crushed to make gypsum powder or synthetic gypsum made to be a
powder, is heated to calcine into stucco, such as by being heated to a
temperature of
generally about 250 F-360 F. With appropriate thermal energy, the gypsum
powder
converts to hemihydrate (CaSO4-1/2H20). If the hemihydrate is exposed to even
greater
thermal energy, the gypsum can convert to soluble anhydrite (CaSO4) or
insoluble
anhydrite (often referred to as "dead burn"). At great enough exposure to
thermal
energy, some of the CaSO4 converts to Ca0 (quicklime), giving the dead burn a
higher
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pH. When calcining gypsum via a process reactor, the primary control mechanism
to
maintain quality is typically to maintain a material (e.g., stucco) output
temperature, of
which the material feed to the calciner and/or the heat to the calciner is
manipulated to
maintain the calciner output control.
[0008] The quality of calcined gypsum can be measured in many ways.
For
example, a manual gravimetric method can be used to measure the amount of
crystal
combined water in the material sample to provide an indication of the degree
of material
calcination that occurred. This measure of the degree of calcination can then
be used
to infer the general phase composition of the calcined gypsum. As a related
example, a
series of manual gravimetric tests of calcined gypsum that has been hydrated
and
heated for different periods of time can be used to produce a calculated phase
composition of the calcined gypsum.
[0009] As another example, thermal temperature profiles of samples
of calcined
gypsum mixed with water are manually monitored, measured, and analyzed. The
water
and calcined gypsum produce an exothermic reaction where different temperature
rates
can be calculated to provide a phase composition of the calcined gypsum.
[0010] As yet another example, near infrared (NIR) equipment can be
used to
measure the amount of crystal combined water in calcined gypsum. The equipment
can
be used manually or in an inline process (such as is described in
International Patent
Application No. WO 2018/091062 Al).
[0011] With the exception of inline NIR, stucco phase measurements
are periodic,
manual samples, requiring a period of time for laboratory testing. The manual
nature of
testing limits the frequency of testing, of which there are periods of time
where quality is
unknown. Furthermore, when tested, there is a lag in results, both of which
limit the
capability to control the calcination process and board formation. The NIR
inline testing
method does not yield true phase composition of the tested material.
[0012] In a typical cementitious board manufacturing process such as
gypsum
wallboard, cementitious board is produced by dispersing calcined gypsum
(commonly
referred to as "stucco") in water to form aqueous calcined gypsum slurry. The
aqueous
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calcined gypsum slurry is typically produced in a continuous manner by
inserting stucco
and water and other additives into a mixer which contains means for agitating
the
contents to form a uniform gypsum slurry. The slurry is continuously directed
toward
and through a discharge outlet of the mixer and into a discharge conduit
connected to
the discharge outlet of the mixer. Aqueous foam can be combined with the
aqueous
calcined gypsum slurry in the mixer and/or in the discharge conduit. A stream
of
foamed slurry passes through the discharge conduit from which it is
continuously
deposited onto a moving web of cover sheet material (i.e., the face sheet)
supported by
a forming table. The foamed slurry is allowed to spread over the advancing
face sheet.
A second web of cover sheet material (i.e., the back sheet) is applied to
cover the
foamed slurry and form a sandwich structure of a continuous wallboard preform.
The
wallboard preform is subjected to forming, such as at a conventional forming
station, to
obtain a desired thickness.
[0013] The calcined gypsum reacts with the water in the wallboard
preform to form a
matrix of crystalline hydrated gypsum or calcium sulfate dihydrate and sets as
a
conveyor moves the wallboard preform down the manufacturing line. The
hydration of
the calcined gypsum provides for the formation of an interlocking matrix of
set gypsum,
thereby imparting strength to the gypsum structure in the gypsum-containing
product.
The product slurry becomes firm as the crystal matrix forms and holds the
desired
shape.
[0014] The quality of the calcined gypsum in terms of its phase
composition of
dihydrate, hemihydrate, and anhydrite (both soluble and insoluble) can have an
influence on the crystalline matrix formation. The phase composition of the
calcined
gypsum may call for the adjustment of the concentration of one or more of the
various
additives known to for use in the board formulation.
[0015] After the wallboard preform is cut into segments downstream
of the forming
station at a point along the line where the preform has set sufficiently, the
segments are
flipped over, dried (e.g., in a kiln) to drive off excess water, and processed
to provide
the final wallboard product of desired dimensions. The aqueous foam produces
air
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voids in the set gypsum, thereby reducing the density of the finished product
relative to
a product made using a similar slurry but without foam. Prior devices and
methods for
addressing some of the operational problems associated with the production of
gypsum
wallboard are disclosed in commonly-assigned U.S. Patent Nos. 5,683,635;
5,643,510;
6,494,609; 6,874,930; 7,007,914; and 7,296,919, which are incorporated by
reference.
[0016] There is a continued need in the art to provide additional
solutions to enhance
the production of cementitious articles. For example, there is a continued
need for
techniques for producing calcined gypsum that yield a consistent proportion of
hemihydrate in the output. As another example, there is a continued need for
techniques for monitoring and controlling the production of calcined gypsum
from a
calciner that yields a consistent phase of calcium sulfate, such as
hemihydrate. And for
example, there is a continued need for techniques for monitoring the
composition
phases of calcined gypsum entering a board line mixer and adjusting and
controlling the
production formulation in response to the composition phases of such calcined
gypsum.
[0017] It will be appreciated that this background description has
been created to aid
the reader and is not to be taken as an indication that any of the indicated
problems
were themselves appreciated in the art. While the described principles can, in
some
aspects and embodiments, alleviate the problems inherent in other systems, it
will be
appreciated that the scope of the protected innovation is defined by the
attached claims
and not by the ability of any disclosed feature to solve any specific problem
noted
herein.
SUMMARY
[0018] In one aspect, the present disclosure is directed to
embodiments of a system
for manufacturing calcined gypsum. In embodiments, a system for manufacturing
calcined gypsum includes a calcination control device with an x-ray analyzer.
[0019] In one embodiment, a system for manufacturing calcined gypsum
includes a
calcination unit and an in-line calcination control device. The calcination
unit includes a
calcining chamber and a heating unit associated with the calcining chamber.
The
calcining chamber includes an inlet for receiving a supply of gypsum
therethrough and
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into the calcining chamber and an outlet for discharging the supply of gypsum
from the
calcining chamber.
[0020] The in-line calcination control device includes an x-ray
analyzer and a
controller in operable arrangement therewith. The x-ray analyzer has an x-ray
source
and a detector. The x-ray source is configured to emit an x-ray beam to strike
at least a
portion of the supply of gypsum in at least one of a position upstream of the
inlet of the
calcining chamber and a position downstream of the outlet of the calcining
chamber.
The detector is configured to measure a response of the supply of gypsum to
the x-rays
emitted from the x-ray source interacting with the gypsum. The x-ray analyzer
is
configured to generate a calcining control signal indicative of the response
measured by
the detector. The controller is configured to adjust at least one operating
parameter of
the calcination unit based upon the calcining control signal received from the
x-ray
analyzer.
[0021] In another aspect, the present disclosure describes
embodiments of a method
of manufacturing calcined gypsum. In embodiments, a method of manufacturing
calcined gypsum includes varying at least one operating parameter based upon a
data
signal received from an x-ray analyzer.
[0022] In yet another aspect, the present disclosure is directed to
embodiments of a
system for manufacturing a gypsum board. In embodiments, a system for
manufacturing a gypsum board includes a board control device with an x-ray
analyzer.
[0023] In one embodiment, a system for manufacturing a gypsum board
includes a
mixer, an ingredient supply system, and an in-line board control device.
[0024] The mixer is adapted to agitate calcined gypsum and water to
form an
aqueous gypsum slurry. The ingredient supply system is configured to
selectively feed,
according to a board formulation, at least water and calcined gypsum to the
mixer. The
ingredient supply system includes a source of calcined gypsum associated with
the
mixer to selectively deliver a feed stream of the calcined gypsum thereto.
[0025] The in-line board control device includes an x-ray analyzer
and a controller in
operable arrangement therewith. The x-ray analyzer has an x-ray source and a
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detector. The x-ray source is configured to emit an x-ray beam to strike at
least a
portion of the feed stream of calcined gypsum in a position upstream of said
at least one
inlet of the mixer. The detector is configured to measure a response of the
feed stream
of calcined gypsum to the x-rays emitted from the x-ray source interacting
with the
calcined gypsum. The x-ray analyzer is configured to generate a board control
signal
indicative of the response measured by the detector. The controller is
configured to
adjust at least one of the board formulation and a board line operational
parameter
based upon the board control signal received from the x-ray analyzer.
[0026] In still another aspect, the present disclosure describes
embodiments of a
method of manufacturing a gypsum board. In embodiments, a method of
manufacturing
a gypsum board includes varying at least one operating parameter based upon a
data
signal received from an x-ray analyzer.
[0027] Further and alternative aspects and features of the disclosed
principles will be
appreciated from the following detailed description and the accompanying
drawings. As
will be appreciated, the systems and techniques for manufacturing calcined
gypsum and
gypsum boards that are disclosed herein are capable of being carried out and
used in
other and different embodiments, and capable of being modified in various
respects.
Accordingly, it is to be understood that both the foregoing general
description and the
following detailed description are exemplary and explanatory only and do not
restrict the
scope of the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The FIGURE is a schematic plan diagram of an embodiment of a system for
manufacturing calcined gypsum constructed in accordance with principles of the
present
disclosure and an embodiment of a system for manufacturing a gypsum board
constructed in accordance with principles of the present disclosure that
includes an
embodiment of a gypsum slurry mixing and dispensing assembly constructed in
accordance with principles of the present disclosure.
[0029] It should be understood that the drawing is not necessarily
to scale and that
the disclosed embodiments are illustrated diagrammatically and in partial
views. In
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certain instances, details which are not necessary for an understanding of
this
disclosure or which render other details difficult to perceive have been
omitted. It
should be understood that this disclosure is not limited to the particular
embodiments
illustrated herein.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0030] The present disclosure provides various embodiments of a
system and a
method for at least one of manufacturing calcined gypsum and manufacturing a
gypsum
board that respectively include means and a step for analyzing calcined gypsum
to
determine the proportion of at least one phase of calcium sulphate (dihydrate,
hemihydrate, anhydrate) contained therein. In embodiments of systems and
methods
for manufacturing calcined gypsum and/or a gypsum board following principles
of the
present disclosure, an in-line control device is provided that includes at
least one x-ray
analyzer.
[0031] In embodiments, an x-ray analyzer is adapted to analyze at
least one of the
calcined gypsum being discharged from a calciner and the calcined gypsum being
fed
into a mixer of a gypsum boardline. The x-ray analyzer is configured to
determine the
proportion of different calcium sulphate phases found therein which can be
used to
control at last one of the calciner and the boardline.
[0032] In embodiments, the means and step for analyzing calcined
gypsum can
comprise equipment for using x-ray diffraction (XRD) and/or x-ray florescence
(XRF) to
analyze a calcium sulfate specimen to measure the presence of different
elements
and/or molecular compounds via spectrometry. The analysis can be used to
determine
the composition of materials in the calcined gypsum.
[0033] In embodiments, the x-ray analyzer comprises any suitable x-
ray analyzer
useful in determining at least one characteristic of calcium sulphate. In
embodiments,
the x-ray analyzer includes an x-ray source and a detector configured to
measure the
response of the calcium sulphate specimen to the x-rays emitted from the x-ray
source
interacting with the calcium sulphate specimen.
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[0034] In embodiments, the x-ray analyzer comprises any suitable XRD
analyzer. In
embodiments, the x-ray analyzer comprises an XRD analyzer configured to
generate x-
ray diffraction data that can be used to determine and measure the contents of
calcium
sulphate, including the proportion of at least one phase of calcium phosphate
present in
the specimen under analysis.
[0035] In embodiments, the x-ray analyzer comprises any suitable XRF
analyzer. In
embodiments, the x-ray analyzer comprises an XRF analyzer configured to
generate x-
ray fluorescence data that can be used to determine and measure the contents
of
calcium sulphate, including the proportion of at least one phase of calcium
phosphate
present in the specimen under analysis.
[0036] X-ray measurements can include known frequencies of peaks
that indicate
certain calcium sulfate derivates (among other elements and compounds). For
example, CaSO4.2H20 at 29.0, 31.0, and/or 33.3 degrees two theta; CaSO4.1/2H20
at
29.4, 29.5, and/or 32.5 degrees two theta; CaS040 25.4, and/or 25.5 degrees
two
theta. These peaks of interest may shift frequencies and/or amplitude when in
the
presence or absence of various compounds and/or elements.
[0037] Certain compounds, such as, salt (e.g., various chloride
derivatives) can have
a negative influence on calcination and board formation. In embodiments, the x-
ray
analyzer comprises an XRF analyzer configured to generate x-ray fluorescence
data
that can be used to determine whether an impurity is present in the calcium
sulphate. In
embodiments, the XRF analyzer is configured to measure the content of at least
one of
salt and chloride in the calcium sulphate being analyzed.
[0038] In embodiments, the calcination control device includes an in-
line XRD
analyzer device configured to detect the amount of different phases of calcium
sulphate
present in a discharge stream from a calciner. In embodiments, the XRD
analyzer
device can be used with any suitable calciner, such as those commercially
available as
readily appreciated by one skilled in the art. Examples of such calciners
include
commercially-available kettles and flash calciners with a bag house discharge.
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[0039] In embodiments, an XRD analyzer device is located at the
discharge of the
calciner to monitor the discharge stream of material being discharged from the
calciner.
In embodiments, the XRD analyzer device is configured to detect the amounts of
the
following phases of calcium sulphate: dihydrate, hemihydrate, and anhydrate
phases. A
specially programmed processor can be configured to create a calcining control
signal
based upon information about the detected phase amounts contained in the x-ray
diffraction data. The calcining control signal can be transmitted to a
calcining controller
which is configured to adjust at least one operating parameter of the calciner
based
upon the amount of different phases of calcium sulphate detected in the
discharge
stream, such as, e.g., the feed rate into the calciner and/or the temperature
profile of the
interior of the calciner. The XRD analyzer device can be used to measure the
content
of dihydrate, hemihydrate, and anhydrate in the discharge stream from the
calciner as
part of a feedback loop for control of the calciner. In embodiments, the
processor can
be a part of the X-ray analyzer or the calcining controller, or can comprise a
part of both
the X-ray analyzer and the calcining controller.
[0040] In embodiments, the processor can be configured to calculate
based upon the
amounts of dihydrate, hemihydrate, and anhydrate detected by the XRD analyzer
device a calculated starting gypsum purity of the feed material fed into the
calciner and
a calculated target calcining profile of dihydrate, hemihydrate, and
anhydrate. In
embodiments, if the amount of anhydrate exceeds a threshold value (e.g., as
compared
to a calculated or predetermined target value), the calcining control signal
generated by
the processor can be configured for use by the calcining controller to direct
the calciner
to cook the feed material less by increasing the feed rate to the calciner
and/or by
reducing the heat profile of the calciner. If the amount of dihydrate exceeds
a threshold
value (e.g., as compared to a calculated or predetermined target value), the
calcining
control signal generated by the processor can be configured for use by the
calcining
controller to direct the calciner to cook the feed material more by decreasing
the feed
rate to the calciner and/or by increasing the heat profile of the calciner.
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[0041] In embodiments, the processor can be configured to use
predictive modeling
using a database of historical measurement of material and calciner control
points to
generate the particular calcining control signal to effect the desired
calciner control. In
embodiments, a bias/re-calibration system can be provided that helps to
maintain
system measuring accuracy as changes in system or materials change the XRD
measuring signals. The bias/recalibration system can include sensor data to
build a
database and statistical model where a bias (offset) fact under various
selected
conditions can be determined and applied to the process control algorithm.
[0042] In embodiments, an XRD analyzer device is located upstream of
the feed inlet
of the calciner to monitor the feed stream of material being fed into the
calciner. In
embodiments, the XRD analyzer device is configured to detect the amounts of
the
following phases of calcium sulphate in the feed stream: dihydrate,
hemihydrate, and
anhydrate phases. In embodiments, the XRD analyzer device is configured to
measure
purity and at least one impurity of the feed stream (e.g., land plaster). In
embodiments,
the processor can be configured to calculate based upon the amounts of
dihydrate,
hemihydrate, and anhydrate detected by the XRD analyzer device in the feed
stream
and the calciner's set points (either as measured or as known by the set
points inputted
to the calciner), a calculated target calcining profile of dihydrate,
hemihydrate, and
anhydrate for the discharge stream. In embodiments, the processor can be
configured
to use analytic modeling to predict the target calcining profile (i.e.,
calculated amounts
of dihydrate, hemihydrate, and anhydrate in the discharge stream) of the
material
discharged from the calciner based upon the amounts of dihydrate, hemihydrate,
and
anhydrate detected by the XRD analyzer device in the feed stream and the
calciner's
set points. In embodiments, the target calcining profile can be used by the
calcining
controller to control the calciner feed rate and/or heat input based upon the
XRD
measurements of the material fed into the calciner to form a feed forward
loop. In
embodiments, the use of the in-line XRD analyzer device to measure different
compositions of gypsum/stuccos can be used by the calcining controller to
control the
calciner to produce a discharge stream from the calciner meeting a specific
quality
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parameter (e.g., a minimum percentage of hemihydrate in the discharge stream)
and/or
to reduce energy usage by the calciner to avoid using more energy than
actually need
to achieve a desired result.
[0043] In embodiments, an XRD analyzer device is located upstream of
the mixer at
a wet end of a gypsum manufacturing boardline to monitor the stucco
composition being
fed into the mixer. In embodiments, the XRD analyzer is preferably interposed
between
a stucco bin and the mixer. The XRD analyzer device can be configured to
monitor the
composition of the stucco fed into the mixer. The detected amounts of
dihydrate,
hemihydrate, and anhydrate can be used by a boardline controller to control
the board
formulation. With the in line XRD analyzer device positioned to monitor the
stucco
stream being fed to the board mixer, it can provide real time monitoring of
stucco
quality, which, via a feed forward loop and analytical modeling performed by
the
processor, can be used by a boardline controller to automatically change the
board
formulation and/or at least one board line operational parameter. For example,
the
board formulation can be automatically controlled based upon the x-ray
diffraction data
from the XRD analyzer device monitoring the stucco feed stream by adjusting
the
amount of at least one of the water and one or more additives being fed to the
board
mixer. Examples of additives whose amounts can be adjusted by the boardline
controller include one or more accelerators (e.g., a heat-resistant
accelerator or
landplaster accelerator), retarder, dispersant, soap, and starch. An example
of a
boardline operational parameter that can be adjusted by the boardline
controller
includes the board line speed. In embodiments, the use of the in-line XRD
analyzer
device to monitor the stucco stream being fed to the mixer can be used to
enhance the
usage of constituent materials comprising the board formulation to reduce raw
material
costs and/or reduce the occurrence of producing gypsum board that does not
satisfy
predetermined specifications.
[0044] Turning now to the Figure, an embodiment of a system 10 for
manufacturing
calcined gypsum and for manufacturing a gypsum board constructed in accordance
with
principles of the present disclosure is shown. The system 10 illustrated in
the Figure
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includes a system 11 for manufacturing calcined gypsum and a system 12 for
manufacturing a gypsum board together to form an integrated manufacturing
environment. In embodiments following principles of the present disclosure, a
system
for manufacturing calcined gypsum or a system for manufacturing gypsum board
constructed according to principles of the present disclosure can be provided
on its
own.
[0045] The illustrated system 11 for manufacturing calcined gypsum
includes a
source of gypsum 20 in the form of land plaster powder, a calcination unit 21
comprising
a calciner 22 with an associated dust collector 23, an in-line calcination
control device
25 having a first x-ray analyzer 27, and a discharge conveyor 28. The
illustrated system
for manufacturing a gypsum board 12 includes an ingredient supply system 30
having a
stucco bin 31 and an elevator 32, an in-line board formation control device 35
having a
second x-ray analyzer 37, and a wet end assembly 38 that includes a mixer 39.
It will
be understood by one skilled in the art that the system 12 for manufacturing a
gypsum
board can include other known subsystems of a gypsum boardline that are not
shown in
FIG. 1, including, e.g., a forming station, a cutting station, a kiln, and
suitable conveying
equipment downstream of the wet end equipment shown in FIG. 1.
[0046] In embodiments, the source of gypsum 20 can be any suitable
gypsum, such
as, for example land plaster as illustrated in FIG. 1. In embodiments, the
source of
gypsum 20 is arranged with an inlet 41 of the calciner 22 to provide a feed
stream of
gypsum to the calciner 22. In the illustrated embodiment, the source of gypsum
20 is
associated with a feeder conveyor 43 to selectively deliver the supply of
gypsum
powder to the calciner 22 via the feeder conveyor 43. The feeder conveyor 43
is
configured to direct the feed stream from the source of gypsum 20 to a
calcining
chamber 44 of the calciner 22 via the inlet 41.
[0047] In embodiments, the calcination unit 21 includes the
calcining chamber 44
and a heating unit 45 associated with the calcining chamber 44 for providing
heat for
calcination. The calcining chamber 44 includes the inlet 41 for receiving a
supply of
gypsum therethrough and into the calcining chamber 44 and an outlet 47 for
discharging
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a discharge stream 48 of calcined gypsum (generally referred to as "stucco")
from the
calcining chamber 44.
[0048] In embodiments, the calcination unit 21 can comprise any
suitable calcination
unit, including any suitable commercially-available calciner as one skilled in
the art
would appreciate, such as, a suitable kettle or flash calciner, for example.
Exemplary
calcining units comprise kettles, which may be indirectly heated, roller
mills, ball mills
and hammer mills. In embodiments, the heating unit 45 of the calcination unit
21
includes at least one burner. Each burner can be operated using any suitable
fuel, such
as, natural gas, petroleum gas, oil, coal, etc. Fuel and air can be introduced
to each
burner of the heating unit 45 to be burned and the hot gases are then provided
in the
calcining chamber 44.
[0049] The calcined gypsum can be ground or milled to a desired
particle size range,
which can be performed separately from calcination and can be performed before
and/or after calcination. Milling and calcining may be performed in
consecutive steps in
different units or may be performed in one stage in a single unit. In
embodiments a
flash calcining unit can be used that performs steps of drying,
grounding/milling, and
calcining in a single stage in a single machine.
[0050] The dust collector 23 is arranged with the calciner 22 to
collect dust emitted
therefrom. In embodiments, the dust collector 23 can be any suitable dust
collector
suitable for abating the amount of dust emitted from the calciner 22.
[0051] The in-line calcination control device 25 includes the x-ray
analyzer 27 and a
controller 50 in operable arrangement therewith. The first x-ray analyzer 27
is arranged
with the discharge stream 48 of the calciner 22. In embodiments, the in-line
calcination
control device 25 is arranged so that the discharge stream 48 of the calciner
22
interacts with the in-line calcination control device 25 in a real-time manner
and at a
position after which the discharge stream 48 has been ground or milled to a
desired
particle size range.
[0052] The first x-ray analyzer 27 has an x-ray source and a
detector. In
embodiments, the x-ray source is configured to emit an x-ray beam to strike at
least a
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portion of the supply of gypsum 20 in at least one of a position upstream of
the inlet 41
of the calcining chamber 44 and a position downstream of the outlet 47 of the
calcining
chamber 44. The detector is configured to measure a response of the supply of
gypsum to the x-rays emitted from the x-ray source interacting with the
gypsum.
[0053] The first x-ray analyzer 27 is configured to generate a
calcining control signal
indicative of the response measured by the detector. The controller 50 is
configured to
adjust at least one operating parameter of the calcination unit 21 based upon
the
calcining control signal received from the first x-ray analyzer 27.
[0054] In embodiments, the calcining control signal generated by the
x-ray analyzer
27 is indicative of the amounts of dihydrate, hemihydrate, and anhydrate
phases in the
supply of gypsum powder. In embodiments, the calcining control signal
generated by
the x-ray analyzer 27 is indicative of the purity of the supply of gypsum,
including
whether at least one impurity is present in the supply of gypsum.
[0055] In embodiments, the first x-ray analyzer 27 can comprise at
least one of an
XRD analyzer device and an XRF analyzer device. In embodiments, the first x-
ray
analyzer 27 comprises both an XRD analyzer device and an XRF analyzer device.
[0056] In embodiments, the x-ray analyzer 27 comprises an XRD
analyzer
configured to generate x-ray diffraction data and to generate, using the x-ray
diffraction
data, the calcining control signal. In embodiments, the calcining control
signal
generated is indicative of the contents of the supply of gypsum, including a
proportion of
at least one phase of calcium phosphate present in the supply of gypsum.
[0057] In embodiments, the x-ray analyzer 27 comprises an XRF
analyzer
configured to generate x-ray fluorescence data and to generate, using the x-
ray
diffraction data, the calcining control signal. The calcining control signal
is indicative of
the contents of the supply of gypsum, including a proportion of at least one
phase of
calcium phosphate present in the supply of gypsum.
[0058] In embodiments, the x-ray analyzer 27 comprises an XRF
analyzer
configured to generate x-ray fluorescence data and to generate, using the x-
ray
diffraction data, the calcining control signal. The calcining control signal
is indicative of
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the contents of the supply of gypsum powder, including whether an impurity is
present
in the supply of gypsum powder. In embodiments, the impurity comprises at
least one
of salt and chloride.
[0059] In embodiments, the first x-ray analyzer 27 is in electrical
communication, via
the controller 50, with the heating unit 45 of the calcination unit 21 and/or
the feeder
conveyor 43 to form a feedback control loop based upon the measured amounts of
dihydrate, hemihydrate, and anhydrate in the discharge stream 48 from the
calciner 22
according to principles discussed herein. In embodiments, the controller 50 is
configured to adjust at least one of a feed rate of the supply of gypsum into
the calcining
chamber 44 and a temperature profile of the calcining chamber 44 based upon
the
calcining control signal received from the first x-ray analyzer 27. In
embodiments, the
controller 50 is configured to control at least one of the feeder conveyor 43
and the
source of gypsum 20 to selectively adjust the feed rate of the supply of
gypsum based
upon the calcining control signal.
[0060] In embodiments, the feedback control loop provided by the
first x-ray analyzer
27 can be used with a variety of calcium sulphate materials, to produce a
discharge
stream 48 from the calciner 22 comprising one or more of the following: water-
soluble
calcium sulfate anhydrite, calcium sulfate a-hemihydrate, calcium sulfate 13-
hemihydrate, natural, synthetic or chemically modified calcium sulfate
hemihydrate,
calcium sulfate dihydrate, and mixtures thereof. In one aspect, the discharge
stream 48
desirably comprises calcined gypsum, such as in the form of calcium sulfate
alpha
hemihydrate, calcium sulfate beta hemihydrate, and/or calcium sulfate
anhydrite. The
calcined gypsum can be fibrous in some embodiments and nonfibrous in other
embodiments. In embodiments, the calcined gypsum can include at least about
50%
beta calcium sulfate hemihydrate. In other embodiments, the calcined gypsum
can
include at least about 86% beta calcium sulfate hemihydrate.
[0061] After calcination, the calcined gypsum can be discharged in
the discharge
stream 48 from the calcination unit 21. In the illustrated embodiment, the
discharge
conveyor 28 transports the discharge stream 48 of calcined gypsum from the
calcination
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unit 21 to the stucco bin 31. In other embodiment, the calcined gypsum can be
transported directly to the boardline without passing through a stucco bin.
The
discharge stream 48 from the calciner 22 can be fed to the stucco bin 31 (if
present) for
storage until the boardline calls for a supply of stucco. In the illustrated
embodiment,
the first X-ray analyzer 27 is located downstream of the outlet 47 of the
calcining
chamber 44 and is configured to monitor at least a portion of the discharge
stream 48 of
calcined gypsum being discharged from the calcination unit 21.
[0062] In embodiments, the ingredient supply system 30 is configured
to selectively
feed, according to a board formulation, at least water 55 and a feed stream 57
of
calcined gypsum to at least one inlet of the mixer 39. The illustrated
ingredient supply
system 30 includes a source of calcined gypsum 31 associated with the mixer 39
to
selectively deliver the feed stream 57 of calcined gypsum to at least one
inlet of the
mixer 39, a source of water 55, a source of soap/foam 59, a source of starch
62, and a
source of heat-resistant accelerator 64. The ingredient supply system 30 can
include a
foam generator system suitable for delivering the supply of foam 59 to the
mixer 39
and/or discharge conduit of the mixer 39 as is well understood by one skilled
in the art.
In other embodiments, the ingredient supply system 30 can include any suitable
dry
ingredient and/or suitable liquid ingredient as will be appreciated by one
skilled in the
art.
[0063] The illustrated ingredient supply system 30 includes the
stucco bin 31 and the
elevator 32. The stucco bin 31 can be associated with the elevator 32 in order
to
selectively supply the wet end assembly 38 with the feed stream 57 of calcined
gypsum.
The elevator 32 is disposed between the stucco bin 31 and the second x-ray
analyzer
37. The elevator 32 is configured to receive the feed stream 57 of calcined
gypsum
from the stucco bin 31, convey the feed stream 57 of calcined gypsum from the
stucco
bin 31 to an elevated position, and discharge the feed stream 57 of calcined
gypsum
therefrom so that the feed stream 57 can be conveyed to the mixer 39 via the
effect of
gravity upon it. In embodiments, the ingredient supply system 30 can include a
suitable
device 69 such as an auger, screw, or similar device for incorporating the
feed stream
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57 of calcined gypsum and at least one other ingredient of the board
formulation
together for introduction into the mixer 39 and appropriate conveyor and/or
ductwork for
facilitating the conveyance of at least one ingredient to an inlet of the
mixer.
[0064] The in-line board control device 35 includes the second x-ray
analyzer 37 and
a controller 70 in operable arrangement therewith. The second x-ray analyzer
37 has
an x-ray source and a detector. The x-ray source is configured to emit an x-
ray beam to
strike at least a portion of the feed stream 57 of calcined gypsum in a
position upstream
of the mixer 39. The detector is configured to measure a response of the feed
stream
57 of calcined gypsum to the x-rays emitted from the x-ray source interacting
with the
calcined gypsum. The x-ray analyzer 37 is configured to generate a board
control
signal indicative of the response measured by the detector. The controller 70
is
configured to adjust at least one of the board formulation and a board line
operational
parameter based upon the board control signal received from the x-ray analyzer
37.
[0065] In embodiments, the board control signal generated by the x-
ray analyzer 37
is indicative of the amounts of dihydrate, hemihydrate, and anhydrate phases
in the
feed stream of calcined gypsum. In embodiments, the board control signal
generated
by the x-ray analyzer 37 is indicative of the purity of the feed stream of
calcined
gypsum, including whether at least one impurity is present in the feed stream
57 of
calcined gypsum.
[0066] The second x-ray analyzer 37 is preferably disposed
downstream of the
elevator and is arranged to monitor the stucco stream being fed to the wet end
assembly, in particular the mixer of the wet end assembly. In embodiments, the
wet
end assembly 38 can include any suitable equipment adapted to mix and/or
assemble
the constituent materials forming the gypsum board.
[0067] In embodiments, the second x-ray analyzer 37 can comprise at
least one of
an XRD analyzer device and an XRF analyzer device. In the illustrated
embodiment,
the second x-ray analyzer comprises both an XRD analyzer device and an XRF
analyzer device. The second x-ray analyzer 37 is in electrical communication
with the
boardline controller 70 which is configured to regulate the board formulation
and the
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operation of boardline equipment, including the ingredient supply system 30,
the mixer
39, and the foam injection system 59.
[0068] In embodiments, the second x-ray analyzer 37 comprises an XRD
analyzer
configured to generate x-ray diffraction data and to generate, using the x-ray
diffraction
data, the board control signal. The board control signal is indicative of the
contents of
the feed stream of calcined gypsum, including a proportion of at least one
phase of
calcium phosphate present in the feed stream of calcined gypsum.
[0069] In embodiments, the XRD analyzer of the second x-ray analyzer
37 is in
electrical communication with the boardline controller 70 to form a forward
control loop
based upon the measured amounts of dihydrate, hemihydrate, and anhydrate in
the
stucco stream being fed to the mixer. For example, the amount of starch in the
board
formulation can be regulated according to the amount of hemihydrate detected
in the
stucco stream. The amount of accelerator in the board formulation can be
adjusted
according to the amount of dihydrate detected in the stucco stream. The amount
of
water in the board formulation can be adjusted according to the proportional
amounts of
dihydrate, hemihydrate, and anhydrate detected in the stucco stream.
[0070] In embodiments, the second x-ray analyzer 37 comprises an XRF
analyzer
configured to generate x-ray fluorescence data and to generate, using the x-
ray
diffraction data, the board control signal. The board control signal is
indicative of the
contents of the feed stream of calcined gypsum, including a proportion of at
least one
phase of calcium phosphate present in the feed stream of calcined gypsum.
[0071] In embodiments, the second x-ray analyzer 37 comprises an XRF
analyzer
configured to generate x-ray fluorescence data and to generate, using the x-
ray
diffraction data, the board control signal. The board control signal is
indicative of the
contents of the feed stream of calcined gypsum, including whether an impurity
is
present in the feed stream of calcined gypsum. In embodiments, the impurity
comprises
at least one of salt and chloride.
[0072] In embodiments, the XRF analyzer device of the second x-ray
analyzer 37
can be used by the processor of the second x-ray analyzer to determine whether
the
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stucco stream contains an amount of salt and/or chloride. The second x-ray
analyzer
37 can send a board control signal to the boardline controller 70 in the event
that
salt/chloride is detected in the stucco stream to the mixer over a certain
threshold to
regulate the operation of the foam injection system 59 arranged with the mixer
39
and/or the discharge conduit thereof.
[0073] The mixer 39 is adapted to agitate the feed stream 57, the
water 55, and
other known additives supplied by the ingredient supply system 30 to form an
aqueous
gypsum slurry which is configured to form the core of the gypsum board. In
embodiments, the mixer 39 includes a housing and an agitator disposed within
the
housing. The agitator can be configured to agitate water and calcined gypsum
to form
an aqueous gypsum slurry. In embodiments, the housing has at least one inlet
for
delivering the water and the calcined gypsum to the mixer 39 and an outlet for
discharging the aqueous gypsum slurry from the housing of the mixer 39.
[0074] In embodiments, the housing defines a mixing chamber, a water
inlet, and a
calcined gypsum inlet. The water inlet and the calcined gypsum inlet are in
communication with the mixing chamber. In embodiments, the housing defines a
plurality of water inlets that are arranged near the calcined gypsum inlet. In
embodiments, the housing defines one or more other water inlets located closer
to the
radial periphery of the housing. In embodiments, the housing defines at least
one
additive inlet for receiving an additive therethrough.
[0075] In embodiments, the mixer 39 is in fluid communication with a
discharge
conduit and the foam injection system 59. Both the water and the stucco stream
can be
supplied to the mixer 39 via one or more inlets as is known in the art. In
embodiments,
any other suitable slurry additive can be supplied to the mixer 39. The weight
ratio of
water to calcined gypsum can be any suitable ratio, although, as one of
ordinary skill in
the art will appreciate, lower ratios can be more efficient because less
excess water will
remain after the hydration process of the stucco is completed to be driven off
during
manufacture, thereby conserving energy. In some embodiments, the gypsum slurry
can
be prepared by combining water and calcined gypsum in a suitable water to
stucco
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weight ratio for board production depending on products, such as in a range
between
about 1:6 and about 1:1, e.g., about 2:3.as is known in the art of
manufacturing
cementitious products.
[0076] In embodiments, one or more inlets can be provided for
introducing other
additives into the mixer 39 in addition to foam that are commonly used in the
production
of gypsum board. Such additives include structural additives including mineral
wool,
continuous or chopped glass fibers (also referred to as fiberglass), perlite,
clay,
vermiculite, calcium carbonate, polyester, and paper fiber, as well as
chemical additives
such as foaming agents, fillers, accelerators, sugar, enhancing agents such as
phosphates, phosphonates, borates and the like, retarders, binders (e.g.,
starch and
latex), colorants, fungicides, biocides, hydrophobic agent, such as a silicone-
based
material (e.g., a silane, siloxane, or silicone-resin matrix), and the like.
Examples of the
use of some of these and other additives are described, for instance, in U.S.
Patent
Nos. 6,342,284; 6,632,550; 6,800,131; 5,643,510; 5,714,001; and 6,774,146; and
U.S.
Patent Application Publication Nos. 2002/0045074; 2004/0231916; 2005/0019618;
2006/0035112; and 2007/0022913.
[0077] In embodiments, the in-line calcination control device 25 and
the in-line board
formation control device 35 can include a processor and a non-transitory
computer
readable medium bearing a calciner control application and a boardline control
application, respectively. In embodiments, each of the first x-ray analyzer 27
and the
second x-ray analyzer 37 includes the processor and the non-transitory
computer
readable medium bearing the calciner control application and the boardline
control
application, respectively. In other embodiments, each of the calcining
controller 50 and
the boardline controller 70 includes the processor and the non-transitory
computer
readable medium bearing the calciner control application and the boardline
control
application, respectively. In other embodiments, the processor respectively
comprises a
part of the first x-ray analyzer 27 and the second x-ray analyzer 37 and the
respective
controller 50, 70. In embodiments, the in-line calcination control device 25
and the in-
line board formation control device 35 can comprise an integrated device
configured to
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perform both calciner control operations and boardline control operations,
positioned at
a point between the calciner and the mixer.
[0078] The processor is in communication with the associated x-ray
analyzer
device(s) 27, 37 to receive the x-ray diffraction data/x-ray fluorescence data
therefrom.
In embodiments, the processor is programmed with at least one of the
particular control
applications.
[0079] In embodiments, the in-line calcination control device 25 and
the in-line board
formation control device 35 can include a user input and/or interface device
having one
or more user-actuated mechanisms (e.g., one or more push buttons, slide bars,
rotatable knobs, a keyboard, and a mouse) adapted to generate one or more user
actuated input control signals. In embodiments, the in-line calcination
control device 25
and the in-line board formation control device 35 can be configured to include
one or
more other user-activated mechanisms to provide various other control
functions for the
calciner and/or boardline, as will be appreciated by one skilled in the art.
The in-line
calcination control device 25 and the in-line board formation control device
35 can
include a display device adapted to display a graphical user interface. The
graphical
user interface can be configured to function as both a user input device and a
display
device in embodiments. In embodiments, the display device can comprise a touch
screen device adapted to receive input signals from a user touching different
parts of
the display screen. In embodiments, processor of the in-line calcination
control device
25 and/or the in-line board formation control device 35 can be in the form of
a smart
phone, a tablet, a personal digital assistant (e.g., a wireless, mobile
device), a laptop
computer, a desktop computer, or other type of device. In embodiments, the
processor
of the in-line calcination control device 25 and the in-line board formation
control device
35 can comprise the same device or be formed from a set of equipment.
[0080] In embodiments, the processor is in operable arrangement with
the non-
transitory computer-readable medium to execute the control application
contained
thereon. The processor can be in operable arrangement with a display device to
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selectively display output information from the control application and/or to
receive input
information from a graphical user interface displayed by the display device.
[0081] In embodiments, the processor can comprise any suitable
computing device,
such as, a microprocessor, a mainframe computer, a digital signal processor, a
portable
computing device, a personal organizer, a device controller, a logic device
(e.g., a
programmable logic device configured to perform processing functions), a
digital signal
processing (DSP) device, or a computational engine within an appliance. In
embodiments, the processor also includes one or more additional input devices
(e.g., a
keyboard and a mouse).
[0082] The processor can have one or more memory devices associated therewith
to
store data and information. The one or more memory devices can include any
suitable
type, including volatile and non-volatile memory devices, such as RAM (Random
Access Memory), ROM (Read-Only Memory), EE PROM (Electrically-Erasable
Programmable Read-Only Memory), flash memory, etc. In one embodiment, the
processor is adapted to execute programming stored upon a non-transitory
computer
readable medium to perform various methods, processes, and modes of operations
in a
manner following principles of the present disclosure.
[0083] In embodiments, the non-transitory computer readable medium
can contain a
control application that is configured to implement an embodiment of a method
for
manufacturing calcined gypsum and/or manufacturing gypsum board according to
principles of the present disclosure. In embodiments, the control application
includes a
graphical user interface that can be displayed by the display device. The
graphical user
interface can be used to facilitate the inputting of commands and data by a
user to the
control application and to display outputs generated by the control
application.
[0084] The control application can be stored upon any suitable
computer-readable
storage medium. For example, in embodiments, a control program following
principles
of the present disclosure can be stored upon a hard drive, floppy disk, CD-ROM
drive,
tape drive, zip drive, flash drive, optical storage device, magnetic storage
device, and
the like.
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[0085] In embodiments, any suitable mixer (e.g., a pin mixer) can be
used in the wet
end. In embodiments, the mixer can be a suitable, commercially-available
mixer, as is
known in the gypsum board manufacturing art, such as, one available from
Gypsum
Technologies Inc. or John Broeders Machine both of Ontario, Canada, for
example.
[0086] In embodiments, the agitator is rotatably mounted within the
mixing chamber.
The agitator can include a radially extending disc to which is attached a
generally
vertical drive shaft positioned along a normal axis, which is perpendicular to
both a
machine direction and a cross-machine direction. The drive shaft can extend
through
the upper wall of the main mixer. The drive shaft can be connected to a
conventional
drive source, such as, a motor, for example, for rotating the drive shaft at a
suitable
speed (e.g., 275-300 rpm) appropriate for rotating the agitator to mix the
contents of the
mixing chamber of the main mixer. This rotation directs the resulting aqueous
slurry in
a generally centrifugal direction, such as in a clockwise outward spiral. It
should be
appreciated that this discussion of an agitator is meant only to indicate the
basic
principles of agitators commonly employed in gypsum slurry mixing chambers
known in
the art. Alternative agitator designs, including those employing pins,
paddles, plows,
rings, etc., are contemplated.
[0087] In embodiments, the weight ratio of water to calcined gypsum
can be any
suitable ratio, although, as one of ordinary skill in the art will appreciate,
lower ratios can
be more efficient because less excess water will remain after the hydration
process of
the stucco is completed to be driven off during manufacture, thereby
conserving energy.
In some embodiments, the gypsum slurry can be prepared by combining water and
calcined gypsum in a suitable water to stucco weight ratio for board
production
depending on products, such as in a range between about 1:6 and about 1:1,
e.g.,
about 2:3.
[0088] In embodiments, a slurry discharge conduit is provided that
is in fluid
communication with the main mixer. In embodiments, the slurry discharge
conduit can
comprise any suitable discharge conduit component as will be appreciated by
one
skilled in the art. For example, the discharge conduit can includes a delivery
conduit, a
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foam injection body of the foam injection system, a flow-modifying element,
and a slurry
distributor.
[0089] In embodiments, the discharge conduit is in fluid
communication with the
main mixer and is configured to deliver a main flow of the core slurry from
the main
mixer downstream to a further manufacturing station. In embodiments, the
discharge
conduit is adapted to deposit the core slurry upon a web of cover sheet
material
advancing in a machine direction. In this arrangement, the gypsum board is
produced
"face down" such that the advancing web serves as the "face" cover sheet of
the
finished board. In embodiments, the core slurry can be discharged from the
discharge
conduit in an outlet flow direction substantially along the machine direction
in which the
moving face cover sheet is travelling.
[0090] In embodiments, the delivery conduit can be made from any
suitable material
and can have different shapes. In some embodiments, the delivery conduit can
comprise a flexible conduit.
[0091] In embodiments, one or more flow-modifying elements can be
associated with
the discharge conduit and adapted to modify the flow of the core slurry
discharged from
the main mixer through the discharge conduit. In embodiments, the flow-
modifying
element is disposed downstream of the foam injection body and the aqueous foam
supply conduit relative to a flow direction of the flow of cementitious slurry
from the main
mixer through the discharge conduit. The flow-modifying element(s) can be used
to
control an operating characteristic of the flow of the core slurry moving
through the
discharge conduit. Examples of suitable flow-modifying elements include volume
restrictors, pressure reducers, constrictor valves, canisters etc., including
those
described in U.S. Patent Nos. 6,494,609; 6,874,930; 7,007,914; and 7,296,919,
for
example.
[0092] In embodiments, the slurry distributor can be any suitable
terminal portion of a
conventional discharge conduit, such as a length of conduit in the form of a
flexible hose
or a component commonly referred to as a "boot." In embodiments, the boot can
be in
the form of a multi-leg discharge boot.
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[0093] In yet other embodiments, the slurry distributor of the
discharge conduit 112
can be similar to one as shown and described in U.S. Patent Application
Publication
Nos. 2012/0168527; 2012/0170403; 2013/0098268; 2013/0099027; 2013/0099418;
2013/0100759; 2013/0216717; 2013/0233880; and 2013/0308411, for example. In
some of such embodiments, the discharge conduit can include suitable
components for
splitting a main flow of cementitious slurry from the main mixer into two
flows which are
re-combined in the slurry distributor.
[0094] In embodiments, a foam injection system is arranged with at
least one of the
main mixer and the slurry discharge conduit. The foam injection system can
include a
foam source (e.g., such as a foam generation system configured as known in the
art), a
foam supply conduit, and a suitable foam injection body.
[0095] In embodiments, any suitable foam source can be used.
Preferably, the
aqueous foam is produced in a continuous manner in which a stream of a mix of
foaming agent and water is directed to a foam generator, and a stream of the
resultant
aqueous foam leaves the generator and is directed to and mixed with the
cementitious
slurry. In embodiments, any suitable foaming agent can be used. Some examples
of
suitable foaming agents are described in U.S. Patent Nos. 5,683,635 and
5,643,510, for
example.
[0096] In embodiments, the aqueous foam supply conduit can be in
fluid
communication with at least one of the main mixer and the delivery conduit. An
aqueous foam from the foam source can be added to the constituent materials
through
the foam supply conduit at any suitable location downstream of the main mixer
in the
discharge conduit and/or in the main mixer itself to form a foamed
cementitious slurry.
In the illustrated embodiment, the foam supply conduit is disposed downstream
of the
main mixer. In embodiments, the aqueous foam supply conduit has a manifold-
type
arrangement for supplying foam to a number of foam injection ports within the
foam
injection body, which can be in the form of an injection ring or block,
associated with the
discharge conduit, such as is described in U.S. Patent No. 6,874,930, for
example.
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[0097] In other embodiments, one or more secondary foam supply
conduits can be
provided, and each of which is in fluid communication with the main mixer. In
yet other
embodiments, the aqueous foam supply conduit(s) can be in fluid communication
with
the main mixer alone. As will be appreciated by those skilled in the art, the
means for
introducing aqueous foam into the gypsum slurry, including its relative
location in the
assembly, can be varied and/or optimized to provide a uniform dispersion of
aqueous
foam in the core slurry to produce board that is fit for its intended purpose.
[0098] In embodiments, the foam injection body comprises a part of
at least one of
the main mixer and the slurry discharge conduit. The illustrated foam
injection body
comprises a part of the discharge conduit.
[0099] In embodiments, one or both of the cover sheets of the gypsum
board can be
treated with a relatively denser layer of gypsum slurry (relative to the core
slurry from
which the board core is made), often referred to as a "skim coat" in the art,
if desired.
To that end, in embodiments, the main mixer can include an auxiliary conduit
that is
adapted to deposit a stream of dense aqueous cementitious slurry that is
relatively
denser than the core slurry deposited from the discharge conduit. In
embodiments, the
denser layer can be provided at the edges of the board, as well, using known
equipment
and techniques.
[00100] In embodiments, the auxiliary conduit comprises one for depositing a
skim
coat layer to a back cover sheet. The main mixer can direct a flow of aqueous
calcined
gypsum slurry through the auxiliary conduit (i.e., a "back skim coat stream")
that is
relatively denser than the main flow of the foamed core slurry dispensed from
the
discharge conduit. A back skim coat station can include suitable equipment for
applying
the back skim coat, such as, for example, a back skim coat roller disposed
over a
support element such that the second cover sheet being dispensed from a second
roll is
disposed therebetween. The auxiliary conduit can deposit the back skim coat
stream
upon the moving second cover sheet upstream (in the direction of movement of
the
second cover sheet) of the back skim coat roller that is adapted to apply a
skim coat
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layer to the second cover sheet being dispensed from the second roll as is
known in the
art.
[00101] In other embodiments, separate auxiliary conduits can be connected to
the
main mixer to deliver one or more separate streams to the face cover sheet.
Other
suitable equipment (such as auxiliary mixers) can be provided in the auxiliary
conduits
to help make the slurry therein denser, such as by mechanically breaking up
foam in the
slurry and/or by chemically breaking up the foam through use of a suitable de-
foaming
agent inserted into the auxiliary conduit(s) through a suitable inlet. In
other
embodiments, an auxiliary conduit can direct slurry from the main mixer into a
second
mixer and/or include a suitable inlet for incorporating at least one enhancing
additive
therein to form a strengthened slurry having at least one ingredient which is
more
concentrated in the strengthened slurry than in the core slurry to form a
slurry suitable
for use as a concentrated layer and/or as edge layer(s).
[00102] In embodiments, the wet end assembly can be equipped with other
conventional equipment as is known in the art. The wet end assembly is
configured to
mix and assemble constituent materials together such that a continuous gypsum
board
having a predetermined nominal thickness can be produced from a forming
station
along a conveyor in the machine direction toward a cutting station. In
embodiments, the
system for manufacturing a gypsum board can include other components and
stations.
For example, in embodiments, the system can include a transfer system,
including a
board inverter; a kiln; and a bundler and taping station, all downstream of
the cutting
station. In embodiments, the board manufacturing process can be completed
using any
suitable techniques and equipment which are known to those skilled in the art.
[00103] All references cited herein are hereby incorporated by reference to
the same
extent as if each reference were individually and specifically indicated to be
incorporated by reference and were set forth in its entirety herein.
[00104] The use of the terms "a" and "an" and "the" and similar referents in
the
context of describing the invention (especially in the context of the
following claims) are
to be construed to cover both the singular and the plural, unless otherwise
indicated
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herein or clearly contradicted by context. The terms "comprising," "having,"
"including,"
and "containing" are to be construed as open-ended terms (i.e., meaning
"including, but
not limited to,") unless otherwise noted. Recitation of ranges of values
herein are
merely intended to serve as a shorthand method of referring individually to
each
separate value falling within the range, unless otherwise indicated herein,
and each
separate value is incorporated into the specification as if it were
individually recited
herein. All methods described herein can be performed in any suitable order
unless
otherwise indicated herein or otherwise clearly contradicted by context. The
use of any
and all examples, or exemplary language (e.g., "such as") provided herein, is
intended
merely to better illuminate the invention and does not pose a limitation on
the scope of
the invention unless otherwise claimed. No language in the specification
should be
construed as indicating any non-claimed element as essential to the practice
of the
invention.
[00105] Preferred embodiments of this invention are described herein,
including the
best mode known to the inventors for carrying out the invention. Variations of
those
preferred embodiments may become apparent to those of ordinary skill in the
art upon
reading the foregoing description. The inventors expect skilled artisans to
employ such
variations as appropriate, and the inventors intend for the invention to be
practiced
otherwise than as specifically described herein. Accordingly, this invention
includes all
modifications and equivalents of the subject matter recited in the claims
appended
hereto as permitted by applicable law. Moreover, any combination of the above-
described elements in all possible variations thereof is encompassed by the
invention
unless otherwise indicated herein or otherwise clearly contradicted by
context.
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