U.S. patent application number 09/942158 was filed with the patent office on 2002-02-21 for non-slumping sprayable refractory castables containing thermal black.
Invention is credited to Cullen, Robert M., Li, Xiangmin.
Application Number | 20020022567 09/942158 |
Document ID | / |
Family ID | 22472222 |
Filed Date | 2002-02-21 |
United States Patent
Application |
20020022567 |
Kind Code |
A1 |
Li, Xiangmin ; et
al. |
February 21, 2002 |
Non-slumping sprayable refractory castables containing thermal
black
Abstract
An essentially non-slumping sprayable refractory castable
composition that is applied without forms is disclosed comprising
(a) a tempered, pumpable first component comprising (i) one hundred
weight percent of a refractory composition comprising from about 60
to 90 weight percent of a refractory aggregate, from about 2 to 25
weight percent of an ultrafine refractory material having an
average particle diameter size less than or equal to about 3
microns, from about 0.5 to 15 weight percent of a binder, and from
about 0.05 to 2.0 weight percent of a dispersant, wherein all or a
portion of the ultrafine refractory material comprises a thermal
black such that the refractory composition comprises from about 2
to 15 weight percent of the thermal black, and (ii) from about 3 to
10 weight percent water based upon 100 weight percent of the
refractory composition; and (b) a second component comprising a
flocculating agent, wherein the second component is added to the
first component for achieving installation of the sprayable
refractory castable composition in an amount to prevent slumping. A
method of installing the sprayable refractory castable composition
is also disclosed.
Inventors: |
Li, Xiangmin; (Pittsburgh,
PA) ; Cullen, Robert M.; (Bethel Park, PA) |
Correspondence
Address: |
Craig G. Cochenour
One Oxford Centre, 20th Floor
301 Grant Street
Pittsburgh
PA
15219
US
|
Family ID: |
22472222 |
Appl. No.: |
09/942158 |
Filed: |
August 29, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09942158 |
Aug 29, 2001 |
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09136295 |
Aug 20, 1998 |
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6313056 |
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Current U.S.
Class: |
501/101 |
Current CPC
Class: |
C04B 35/66 20130101 |
Class at
Publication: |
501/101 |
International
Class: |
C04B 035/52 |
Claims
We claim:
1. An essentially non-slumping, high density, low moisture
sprayable refractory castable composition that is applied without
the use of forms comprising: (a) a tempered, pumpable first
component comprising (i) 100 weight percent of a refractory
composition, said refractory composition comprising from about 60
to 90 weight percent of a refractory aggregate wherein said
refractory aggregate comprises alumina, from about 2 to 25 weight
percent of an ultrafine refractory material having an average
particle diameter size less than or equal to about 3 microns, and
from about 0.05 to 2.0 weight percent of a dispersant, wherein all
or a portion of said ultrafine refractory material comprises a
thermal black such that said refractory composition comprises from
about 2 to 15 weight percent of said thermal black, and (ii) from
about 3 to 10 weight percent water based upon 100 weight percent of
said refractory composition, wherein said water is present in an
amount sufficient to achieve a pumpable consistency; and (b) a
second component comprising a flocculating agent, wherein said
second component is added to said first component for achieving
installation of the sprayable refractory castable composition in an
amount to prevent slumping.
3. The sprayable refractory castable composition of claim 1
comprising from about 2 to 15 weight percent of said ultrafine
refractory material and wherein all of said ultrafine refractory
material is said thermal black.
4. The sprayable refractory castable composition of claim 1 wherein
said ultrafine refractory material comprises said thermal black and
at least one of an alumina, a titania, a bauxite, a diaspore, a
mullite, an aluminous shale, a chamotte, a pyrophyllite, a
sillimanite, an andalusite, a graphite, a carbonaceous material, a
rare earth oxide, a silica rock, an amorphous silica, a fumed
silica, a microsilica, a silica fume, a zirconia, a zircon, a
chromic oxide, a silicon nitride, an aluminum nitride, a silicon
carbide, a boron carbide, a zirconium boride, a titanium boride, a
magnesium oxide, a magnesite, a deadburned magnesite, a spinel, and
combinations thereof.
6. The sprayable refractory castable composition of claim 1 wherein
said dispersant comprises an anionic dispersing agent.
7. The sprayable refractory castable composition of claim 1 wherein
said anionic dispersing agent comprises at least one of a
polymerized alkyl naphthalene sulfonic acid, a modified lignin, and
salts thereof.
8. The sprayable refractory castable composition of claim 1 wherein
said thermal black is an American Society for Testing and Materials
(ASTM) Designation 1765-96 having an average nitrogen surface area
defined by Classification Group Numbers 8 and 9 of said ASTM
Designation D1765-96.
9. The sprayable refractory castable composition of claim 1 wherein
said flocculating agent is one of the agents selected from the
group of an alkali chloride, an alkaline-earth chloride, an alkali
phosphate, a calcium hydroxide, a calcium oxide, a calcium
aluminate, a potassium aluminate, and an alkali silicate.
10. The sprayable refractory castable composition of claim 9
wherein said alkaline-earth chloride is calcium chloride.
11. The sprayable refractory castable composition of claim 9
wherein said alkali phosphate is dipotassium phosphate.
12. The sprayable refractory castable composition of claim 1
wherein the amount of said flocculating agent added for each 100
weight percent of said first component castable solids is from
about 0.1 to 2.5 weight percent.
13. The sprayable refractory castable composition of claim 1
further comprising at least one plasticizer.
14. The sprayable refractory castable composition of claim 1
further comprising from about 1 to 10 weight percent of at least
one metal.
15. The sprayable refractory castable composition of claim 1
further comprising from about 0.1 to 1.0 weight percent of at least
one fiber.
18. The sprayable refractory castable composition of claim 1
wherein said tempered, pumpable first component further comprises
from about 0.5 to 15 weight percent of a binder.
19. The sprayable refractory castable composition of claim 18
wherein said binder comprises at least one of a calcium-aluminate
cement, a phenolic resin, a pitch, an alkali silicate, a
phosphate-modified alumina silicate, and combinations thereof.
20. The sprayable refractory castable composition of claim 19
wherein said binder is a calcium-aluminate cement, said dispersant
is a modified lignin, and said flocculating agent is calcium
chloride.
21. The sprayable refractory castable composition of claim 18
further comprising at least one plasticizer.
22. The sprayable refractory castable composition of claim 18
further comprising from about 1 to 10 weight percent of at lest one
metal.
23. The sprayable refractory castable composition of claim 18
further comprising from about 0.1 to 1.0 weight percent of at least
one fiber.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a refractory composition and
castable. The refractory composition comprises a refractory
aggregate, an ultrafine refractory material having an average
particle diameter size less than or equal to about 3 microns, a
binder, and a dispersant, wherein all or a portion of the ultrafine
refractory material comprises thermal black. This invention also
relates to a refractory castable composition comprising the
refractory composition of the instant invention and water in an
amount sufficient to achieve a castable consistency for casting the
refractory castable composition with the use of forms.
[0003] Further, this invention relates to an essentially
non-slumping, high density, low moisture sprayable refractory
castable composition which can be applied without forms,
comprising, a tempered, pumpable first component comprising the
refractory castable composition as disclosed herein, and a second
component comprising at least one flocculating agent that is added
to the first component at the time of installation of the sprayable
refractory castable composition in an amount to prevent slumping. A
method of applying the essentially non-slumping, high density, low
moisture sprayable refractory castable composition is provided.
[0004] 2. Brief Description of the Background Art
[0005] A considerable amount of work has been done by those skilled
in the art to improve the properties of refractory castables. For
example, much work has been done to lower the water content
required for casting calcium aluminate cement bonded high alumina
and fireclay refractory castables. It is well known by those
skilled in the art that a reduction in the water content required
for casting leads to higher density and lower porosity, ultimately
resulting in refractory castables that perform better in
service.
[0006] The reduction in water content required for casting
refractory castables has resulted from the use of dispersants and
ultrafine particles in combination with particle packing
principles. The dispersants minimize formation of flocs that raise
water requirements. More optimum particle packing has been achieved
by using progressively finer particles to fill in the voids between
the coarser aggregates. Without these ultrafine particles, the
voids between the coarser aggregates would fill with water during
casting, thus, increasing the amount of water needed in the
refractory castable. It will be appreciated by those skilled in the
art that a substantial reduction in the amount of water required
for casting refractory castables was realized with the discovery
that ultrafine particles (i.e. particles having a diameter of less
than about three microns) could be included in the products when
used with appropriate dispersants. The ultrafine particles used for
this purpose have been ultrafine refractory materials, namely,
oxides, such as for example, microsilica and finely ground alumina
being the most common choices. European Patent EP 0742416
(hereinafter EP '416) discloses a spray operation method for
monolithic refractories wherein a fine powder of alumina or fumed
silica having a particle size of at most three microns imparts good
flowability to the mixed batch of monolithic refractories. U.S.
Pat. No. 5,549,745 (Langenohl et al.) (hereinafter U.S. Pat. No.
'745) and U.S. Pat. No. 5,512,325 (Langenohl et al) (hereinafter
U.S. Pat. No. '325) disclose a non-slumping, high density, low
moisture, low cement sprayable refractory castable composition
which can be applied without forms containing a solid flow aid that
is microsilica, 1 to 3 micron alumina, or mixtures thereof.
[0007] Despite their effectiveness in lowering water requirements
for casting, there are drawbacks to using microsilica and ultrafine
alumina. For example, microsilica typically reduces high
temperature refractoriness of refractory castables. In high alumina
and fireclay castables bonded with calcium aluminate cement, for
example, the microsilica combines with lime from the calcium
aluminate cement when the castable is heated, forming low melting
point glasses. These glasses cause major disadvantages such as for
example, but not limited to, making the castable more prone to
creep at high temperatures, decreasing the hot strength and
increasing the susceptibility of the castable to chemical
corrosion. In an attempt to deal with the problem of glass
formation, refractory compositions with either no calcium aluminate
cement, or reduced levels of calcium aluminate cement have been
developed. The resulting lower lime contents reduce the amount of
low melting glass that forms, but refractoriness is still not
optimized because the microsilica in the matrix of the castable
remain susceptible to chemical alteration and fluxing by
constituents commonly found in the environments in which the
castables were used. Ultrafine alumina, when used to reduce the
water required for casting refractory castables, is a substantial
commercial impediment because of its high cost. In addition,
ultrafine alumina can have a detrimental effect on the rheology of
refractory castables, in particular those that are bonded with
calcium aluminate cement. Refractory castables containing calcium
aluminate cement and ultrafine alumina can exhibit short working
times and poor casting characteristics. While not fully understood,
it is believed that the ultrafine alumina provides nucleation sites
for precipitation of hydrate phases from solution during mixing and
placement of the castables. It is known by those skilled in the art
that alumina-lime hydrate phases form on the edges of ultrafine
alumina particles in suspensions of ultrafine alumina and calcium
aluminate cement in water. It is believed that these hydrate phases
affect the morphology of the finest constituents in the refractory
castables, thereby adversely affecting rheology and casting
characteristics.
[0008] Other ultrafine refractory oxides for reducing the amount of
water required for casting refractory castables have similar
drawbacks. For example, ultrafine chromic oxide is expensive and is
undesirable from an environmental standpoint. Ultrafine titania is
also expensive and is generally regarded as a flux in refractory
systems. Thus, despite the ability of various ultrafine refractory
oxides to reduce the water required for casting refractory
castables, no ultrafine refractory material heretofore has been
found that is wholly satisfactory from either a technical,
environmental, or economic standpoint Further, it will be
appreciated by those skilled in the art, that no ultrafine
refractory material heretofore has been found that provides for
reducing the amount of conventional ultrafine refractory oxides
employed or for eliminating the use of conventional ultrafine
refractory oxides to fill in the voids between the coarser
refractory aggregates while at the same time maintaining particle
packing principles for reducing the water content required for
casting.
[0009] Therefore, in spite of this background material, there
remains a very real and substantial need for a refractory
composition, castable, and spray mix having an ultrafine refractory
material that is capable of lowering the amount of water required
for casting or spraying the refractory castable composition while
at the same time reducing or eliminating the undesirable
characteristics of the ultrafine refractory particles disclosed by
the background art.
SUMMARY OF THE INVENTION
[0010] The present invention has met the above-described needs. The
present invention provides a refractory composition comprising a
refractory aggregate, an ultrafine refractory material having an
average particle size diameter less than or equal to about 3
microns, a binder, and a dispersant and wherein all or a portion of
the ultrafine refractory material comprises a thermal black such
that the refractory composition comprises from about 2 to 15 weight
percent thermal black. The present invention further provides a
refractory castable composition comprising the refractory
composition of this invention as described herein and water present
in an amount sufficient to achieve a castable consistency.
[0011] Another embodiment of the present invention provides a
method of using the refractory castable composition with forms or
molds to produce a castable refractory product of a desired shape.
This method provides for the manufacture of a castable refractory
product comprising casting the refractory castable composition of
the instant invention as described herein, to form a refractory
shape or lining.
[0012] In another embodiment of this invention, an essentially,
non-slumping, high density, low moisture sprayable refractory
castable composition is provided that is applied without forms.
This sprayable refractory castable composition of the present
invention comprises (a) a tempered, pumpable first component
comprising 100 weight percent of the refractory castable
composition, as disclosed herein, and (b) a second component
comprising a flocculating agent. The flocculating agent is added to
the first component of the sprayable refractory castable
composition for achieving installation of the sprayable refractory
castable composition in an amount sufficient to prevent
slumping.
[0013] Another embodiment of this invention provides a method of
applying the essentially, non-slumping, high density, low-moisture
sprayable refractory castable composition of the present invention,
as described herein, on a surface without the use of forms, with a
pump means and an associated hose means and an associated nozzle
means comprising (a) preparing a tempered pumpable first component
comprising (i) 100 weight percent of a refractory composition
comprising a refractory aggregate, an ultrafine refractory material
having an average particle diameter size less than or equal to
about three microns, a binder, and a dispersant and wherein all or
a portion of the ultrafine refractory material comprises a thermal
black such that the refractory composition comprises from about 2
to 15 weight percent thermal black, and (ii) from about 3 to 10
weight percent water based upon 100 weight percent of the
refractory composition, wherein the water is present in an amount
sufficient to achieve a pumpable consistency of the first component
to enable the first component to be pumped and applied through the
pump means, the hose means and the nozzle means, (b) adding a
second component comprising a flocculating agent to the first
component to form a refractory castable composition, wherein the
flocculating agent is added to the first component at or prior to
the time of the application of the refractory castable composition
through the nozzle means, (c) introducing air through the nozzle
means just prior to the time of the application of the refractory
castable composition and (d) applying the refractory castable
composition to the surface without the use of forms
DETAILED DESCRIPTION
[0014] The present invention provides a refractory composition
comprising from about sixty (60) to ninety (90) weight percent of a
refractory aggregate, from about two (2) to twenty-fifty (25)
weight percent of an ultrafine refractory material having an
average particle diameter size of less than or equal to about three
(3) microns, from about one-half (0.5) to fifteen (15) weight
percent of a binder, and from about five one-hundredth (0.05) to
two (2.0) weight percent of a dispersant, wherein all or a portion
of the ultrafine refractory material comprises a thermal black such
that the refractory composition comprises from about two (2) to
fifteen (15) weight percent thermal black.
[0015] Another embodiment of the instant invention provides a
refractory castable composition comprising (a) one-hundred (100)
weight percent of a refractory composition comprising from about
sixty (60) to ninety (90) weight percent of a refractory aggregate,
from about two (2) to twenty-five (25) weight percent of an
ultrafine refractory material having an average particle diameter
size less than or equal to about three (3) microns, from about
one-half (0.5) to fifteen (15) weight percent of a binder, and from
about five one-hundredth (0.05) to two (2.0) weight percent of a
dispersant, wherein all or a portion of the ultrafine refractory
material comprises a thermal black such that the refractory
composition comprises from about two (2) to fifteen (15) weight
percent of the thermal black, and (b) from about three (3) to ten
(10) weight percent water based upon one hundred (100) weight
percent of the refractory composition, wherein the water is present
in an effective amount sufficient to achieve a castable
consistency.
[0016] As used herein, the term "effective amount" refers to that
amount of a substance necessary to bring about a desired result,
such as, for example, the amount of water needed to achieve a
consistency suitable for installing the refractory castable
composition of the present invention, such as for example, casting,
pumping, spraying and combinations thereof.
[0017] The refractory aggregate used in the instant invention can
be any suitable for linings for metallurgical vessels. For example,
but not limited to, the refractory aggregate comprises at least one
of an alumina, a tabular alumina, a fused alumina, a calcined
alumina, a sintered alumina, a bauxite, a bauxitic kaolin, a
diaspore, a mullite, an aluminous shale, a chamotte, a silica rock,
a pyrophyllite, a sillimanite, a crude andalusite, a calcined
andalusite, a calcined fire clay, a crude kyanite, a calcined
kyanite, a zirconia, a zircon, a chromic oxide, a silicon nitride,
a graphite, a carbonaceous material, a vitreous silica, a fused
silica, an aluminum nitride, a silicon carbide, a boron carbide, a
titanium boride, a zirconium boride, a magnesium oxide, a
magnesite, a deadburned magnesite, a spinel, a rare earth oxide,
and combinations thereof, and other like refractory aggregates.
[0018] The ultrafine refractory material used in the instant
invention can be any suitable for linings of metallurgical vessels.
For example, but not limited to, the ultrafine refractory material
comprises a thermal black alone or in combination with at least one
of an alumina, a titania, a bauxite, a diaspore, a mullite, an
aluminous shale, a chamotte, a pyrophyllite, a sillimanite, an
andaulsite, a silica rock, an amorphous silica, a fumed silica, a
microsilica, a silica fume, a zirconia, a zircon, a chromic oxide,
a silicon nitride, a graphite, a carbonaceous material, an aluminum
nitride, a silicon carbide, a boron carbide, a zirconium boride, a
titanium boride, a magnesium oxide, a magnesite, a deadburned
magnesite, a spinel, a rare earth oxide, and combinations thereof,
and other like ultrafine refractory powders. The ultrafine
refractory material of this invention has an average particle
diameter size of less than or equal to three (3) microns. All or a
portion of the ultrafine refractory material of the instant
invention comprises a thermal black such that the refractory
composition comprises from about two (2) to fifteen (15) weight
percent thermal black.
[0019] The binder used in the instant invention can be any suitable
for linings of metallurgical vessels. For example, but not limited
to, the binder comprises at least one of a calcium aluminate
cement, a phenolic resin, pitch, an alkali silicate, a
phosphate-modified aluminum silicate, and combinations thereof, and
other like binders. The alkali silicate is, such as, for example,
sodium silicate or potassium silicate. The phosphate-modified
aluminum silicate is commercially available as "LITHOPIX AS 85"
from Zschimmer & Schwarz Gmbh. & Co., D-5420 Lahnstein,
Rhein, Germany.
[0020] The calcium aluminate cement can be any hydraulic setting
calcium aluminate cement, and preferably is utilized at a
concentration of about 1 to 15 weight percent (wt %). Such calcium
aluminate cements contain mainly calcium aluminate phases, although
in some cases alumina and/or rheological agents are added. Calcium
aluminate cements are commercially available such as, for example,
having about 40 to 90 weight percent (wt. %) alumina and about 10
to 35 wt. % calcia.
[0021] It is preferable in the instant invention to use high purity
calcium aluminate cements such as, for example, those containing
virtually only calcium aluminate phases and alumina without any
rheology additives. Commercially available high purity calcium
aluminate cements contain, such as, for example, about 70 weight
percent alumina and about 30 weight percent calcia, such as, for
example, "CA-14" available from ALCOA, Pittsburgh, Pa., and "SECAR
71" available from Lafarge Calcium Aluminates, Inc., Chesapeake,
Va.
[0022] A cement-free binder may also be used as the binder in the
refractory compositions and castables of the instant invention
either alone, in combination with each other, or in combination
with the calcium-aluminate cement as described herein. Such
cement-free binders are well known by those skilled in the art and
include such as, for example, but not limited to complex phosphates
such as the hereinbefore mentioned phosphate-modified aluminum
silicate, alkali silicates, organic resins or pitch. Preferably,
the cement-free binder is a resin such as, for example, a phenolic
resin, a pitch, or a combination thereof.
[0023] As stated hereinbefore, by employing an ultrafine refractory
material having all or a portion thereof comprising thermal black,
the instant invention overcomes the limitations and disadvantages
of ultrafine particles previously used by those skilled in the art
such as, for example, microsilica, ultrafine alumina (i.e. alumina
having a particle diameter from about 0 5 to 3 microns), chromic
oxide and titania. It is generally well known by those skilled in
the art that ultrafine particles, such as microsilica, and
ultrafine alumina, in combination with suitable dispersants, reduce
the water requirements for casting refractory castable
compositions. As stated herein, the ultrafine particles utilized by
those skilled in the art prior to the instant invention, although
capable of reducing the amount of water needed for casting the
refractory composition, have certain disadvantages. For example,
microsilica decreased the refractoriness of the composition or made
it more susceptible to chemical attack. In addition, ultrafine
alumina can detrimentally effect the rheology of the refractory
castable composition. By employing a refractory composition
comprising from about 2 to 15 weight percent thermal black having
an average particle diameter size less than or equal to about 3
microns, the use of known conventional ultrafine particles can be
effectively reduced or eliminated.
[0024] The thermal black of the instant invention is a specific
type of carbon black made from natural gas or for example, but not
limited to, the pyrolysis of bituminous coal. Preferably, the
thermal black of the instant invention is an American Society for
Testing and Materials (ASTM) Designation 1765-96 thermal black
having an average nitrogen surface area from about 0 to 20 square
meters per gram as defined by Classification Group Nos. 8 and 9 of
the ASTM Designation 1765-96. Preferably, the refractory
composition of the instant invention comprises about five (5)
weight percent thermal black. As will be appreciated by those
skilled in the art, thermal black is available from different
sources and can be used in pelletized versions. Pelletized versions
of thermal black are used with appropriate mixing to break down the
pellets so that the desired effect can be achieved in the
refractory composition. The thermal black source may be, for
example, a natural gas source, such as the N-990 type (ASTM)
thermal blacks commercially available from Cancarb Limited,
Medicine Hat, Alberta, Canada, or Engineered Carbons, Inc., Borger,
Tex. It is important for those persons skilled in the art to
understand that the present inventors have unexpectantly found that
thermal blacks when employed as the ultrafine refractory material
in the refractory composition of the instant invention provide for
the reduction in water required for casting of the refractory
composition and also improve the physical properties of the
resulting refractory castable product. Further the present
inventors have found that other forms of carbon black in the form
of ultrafine refractory material such as for example, furnace
blacks do not produce the unexpected benefits provided by the
thermal blacks of the instant invention.
[0025] With respect to the dispersant of the instant invention, it
must be able to disperse the thermal black as well as the other
constituents of the refractory castable composition when water is
added to the refractory castable composition. Combinations of
dispersants are sometimes desirable depending on the specific
constituents in the refractory castable composition. The
dispersant(s) employed in the instant invention is a dispersant(s)
known to those skilled in the art and include such as, for example,
but not limited to anionic dispersing agents. Examples of anionic
dispersing agents include, for example, but not limited to,
polymerized alkyl naphthalene sulfonic acids and salts thereof and
modified lignins such as, for example, lignosulfonates and salts
thereof. The polymerized alkyl naphthalene sulfonic acid is
commercially available as the sodium salt form under the trade name
"DAXAD 11" commercially available from W. R. Grace & Co.,
Lexington, Mass. The modified lignins of the instant invention may
be used in liquid and powder forms and may be derived from the
kraft pulping process or the sulfite pulping process known by those
skilled in the art. The modified lignins used in the instant
invention, may be, for example, but not limited to, fractionated
lignins in terms of molecular weight, purified or may be used in
either the protonated or salt forms. Preferably, the modified
lignin is a purified desulphonated sodium lignosulfonate, such as,
for example, that is commercially available under the trade name
"MARASPERSE CBA-1" from LignoTech USA, Inc., Bridgewater, N.J.
Other forms of the modified lignin of the instant invention include
such as, for example, but not limited to calcium lignosulfonates
available commercially in a liquid form and a solid form under the
trade names "NORLIG H" and "WAFEX" respectively, from LignoTech
USA, Inc, Bridgewater, N.J.
[0026] The refractory composition of the instant invention has for
each 100 weight percent of the castable solids of the refractory
composition from about 0.05 to 2.0 weight percent dispersant, and
more preferably about 0.2 weight percent dispersant.
[0027] It will be appreciated by those persons skilled in the art
that other additives may be used in combination with the
dispersants of the instant invention to affect the rheology of the
castable. Such additives include such as, for example, but not
limited to, boric acid or citric acid retarders. Such additives are
added in the amount from about 0.01 to 1.0 weight percent for each
100 weight percent of the castable solids of the refractory
castable composition.
[0028] The amount of water used in the refractory castable
composition of the instant invention is the effective amount needed
to achieve a castable consistency of the constituent components of
the base mix (i.e. refractory aggregate, ultrafine refractory
material, binder, and dispersant) of the refractory castable
composition such as, for example, from about 3.0 to 10.0 weight
percent water for each 100 weight percent of the constituent
components of the base mix of the refractory castable composition.
More preferably from about 3.0 to 7.0 weight percent water for each
100 weight percent of the constituent components of the base mix of
the refractory castable is employed to attain the highest possible
density and strength of the resulting refractory castable while
also ensuring proper flow during casting.
[0029] In another embodiment of the instant invention, at least one
metal is added to the refractory compositions and castables, as
described herein. The metal is, such as, for example, aluminum,
silicon, and magnesium, and alloys thereof, and/or combinations
thereof The metals are used in powdered or granular form. The
metals, in addition to inhibiting carbon oxidation at elevated
temperatures, react with the thermal black at temperatures above
about 1470.degree. Fahrenheit (F.) to form carbides which enhance
bonding and therefore increase the strength of the refractory
castable composition of the instant invention. The metal additions
are employed from about one to ten weight percent (wt. %) based
upon one hundred weight percent of the refractory composition.
[0030] In another embodiment of the instant invention, a refractory
composition is provided, as described herein, that further
comprises the addition of fibrous material compatible with
refractory compositions as known by those skilled in the art, such
as for facilitating the removal of moisture upon heating. The
fibrous material is, for example, but not limited to vinyl acetate
and vinyl chloride fibers commercially available under the trade
name "Vinyon" from Waker USA, Norvalk, Conn. The fibrous material
additions are employed from about one-tenth (0 1 ) to one (1 0)
weight percent based upon one hundred (100) weight percent of the
refractory composition.
[0031] Another embodiment of the present invention provides a
method of using the refractory castable composition with forms or
molds to produce a castable refractory product of a desired shape.
This method provides for the manufacture of a castable refractory
product comprising casting the refractory castable composition of
the instant invention as described herein to form a refractory
shape or lining.
[0032] In another embodiment of this invention, an essentially,
non-slumping, high density, low moisture sprayable refractory
castable composition is provided that is applied without forms.
This sprayable refractory castable composition of the present
invention comprises (a) a tempered, pumpable first component
comprising (i) 100 weight percent of a refractory castable
composition wherein the refractory castable composition comprising
from about 60 to 90 weight percent of a refractory aggregate, from
about 2 to 25 weight percent of an ultrafine refractory material
having an average particle diameter size less than or equal to
about 3 microns, from about 0.5 to 15 weight percent of a binder,
and from about 0.05 to 2.0 weight percent of a dispersant, wherein
all or a portion of the ultrafine refractory material comprises a
thermal black such that the refractory composition comprises from
about 2 to 15 weight percent of the thermal black, and (ii) from
about 3 to 10 weight percent water based upon 100 weight percent of
the refractory composition, wherein the water is present in an
amount sufficient to achieve a pumpable consistency; and (b) a
second component comprising a flocculating agent. The flocculating
agent is added to the first component of the sprayable refractory
castable composition at or prior to the installation of the
sprayable refractory castable composition to a surface without the
use of forms. The flocculating agent is added to the first
component in an amount to prevent slumping. Preferably, the amount
of flocculating agent added for each 100 weight percent of the
first component castable solids is from about 0 1 to 2.5 weight
percent.
[0033] The flocculating agent used in the instant invention can be
any suitable for refractory use. For example, but not limited to,
the flocculating agent comprises at least one of the agents
selected from the group of an alkali chloride, an alkaline-earth
chloride, an alkali phosphate, a calcium hydroxide, a calcium
oxide, a calcium aluminate, a potassium aluminate, and an alkali
silicate. Preferably, the flocculating agent is an alkaline-earth
chloride, such as for example, calcium chloride, or an alkali
phosphate, such as for example, dipotassium phosphate.
[0034] In another embodiment of the present invention, the
sprayable refractory castable composition as disclosed herein is
provided further comprising from about 1.0 to 10 weight percent of
at least one metal, as disclosed herein.
[0035] In yet another embodiment of the instant invention, the
sprayable refractory castable composition, as disclosed herein,
further comprises at least one of a plasticizer (i.e. such as, for
example, a ball clay), a retardant agent (i.e. such as, for
example, citric acid or boric acid retarders), a fibrous material,
and combinations thereof, as will be appreciated and in amounts
known by those skilled in the art.
[0036] Another embodiment of the present invention provides a
method of applying the essentially, non-slumping, high density,
low-moisture sprayable refractory castable composition of the
present invention, as described herein, on a surface without the
use of forms, with a pump means and an associated hose means and an
associated nozzle means comprising (a) preparing a tempered
pumpable first component comprising (i) 100 weight percent of a
refractory composition comprising a refractory aggregate, an
ultrafine refractory material having an average particle diameter
size less than or equal to about three microns, a binder, and a
dispersant and wherein all or a portion of the ultrafine refractory
material comprises a thermal black such that the refractory
composition comprises from about 2 to 15 weight percent thermal
black, and (ii) from about 3 to 10 weight percent water based upon
100 weight percent of the refractory composition, wherein the water
is present in an amount sufficient to achieve a pumpable
consistency of the first component to enable the first component to
be pumped and applied through the pump means, the hose means and
the nozzle means, (b) adding a second component comprising a
flocculating agent to the first component to form a sprayable
refractory castable composition, wherein the flocculating agent is
added to the first component to form the sprayable refractory
castable composition at or just prior to the time of application of
the sprayable refractory castable composition, (c) introducing air
through the nozzle means just prior to the time of the application
of the sprayable refractory castable composition, and (d) applying
the sprayable refractory castable composition to a surface without
the use of forms. Preferably, the method as disclosed herein,
comprises adding the flocculant agent to the first component
through the nozzle means to form the sprayable refractory castable
composition just prior to the time of application of the sprayable
refractory castable composition through the nozzle means. It will
be understood by those persons skilled in the art that in another
embodiment of the present invention, a method of applying the
sprayable refractory castable composition, as disclosed herein, is
provided comprising adding the flocculating agent to the first
component at a point upstream from the nozzle means, such as for
example, through the hose means.
[0037] It will be appreciated by those skilled in the art that
another embodiment of the method of applying the sprayable
refractory castable composition of the present invention comprises
adding at least one metal, as disclosed herein, to the sprayable
refractory castable composition. Further, the method of the instant
invention further comprises adding at least one of a plasticizer, a
retardant agent, and a fibrous material, and combinations thereof,
as disclosed herein, in amounts known by those skilled in the art,
to the sprayable refractory castable composition of the present
invention.
EXAMPLES
[0038] The following examples demonstrate the instant invention in
greater detail. These examples are not intended to limit the scope
of the instant invention in any way. In the examples, the following
products were used.
[0039] Tabular Alumina is a refractory aggregate having greater
than or equal to about ninety-nine weight (99 0) percent aluminum
oxide material commercially available from Aluminum Company of
America, Pittsburgh, Pa., and is preferably used as a -3 mesh
fraction (7 10 millimeter) and finer particles to provide a size
distribution for optimum flow characteristics and density, as will
be understood by those persons skilled in the art.
[0040] The Reactive Aluminas are ultrafine refractory material
about 0.4 micron and 3.0 microns average particle diameter size,
respectively, and are greater than or equal to ninety-nine (99.0)
weight percent aluminum oxide material, commercially available
under the trade names "A-1000-SGD" and "A-3000-FL", respectively,
from Aluminum Company of America, Pittsburgh, Pa.
[0041] Calcium Aluminate Cement is a 70 percent alumina and 30
percent calcia cement commercially available under the trade name
"SECAR 71" from Lafarge Aluminates, Inc., Chesapeake, Va.
[0042] Microsilica is a 0.5 micron average particle size
microsilica commercially available under the trade name "EMS 965"
from Elkem Materials, Inc., Pittsburgh, Pa.
[0043] The thermal black is "Thermax Floform N-990", commercially
available from Cancarb Limited, Medicine Hat, Alberta, Canada, or
"N-990 Thermal Carbon Black", commercially available from
Engineered Carbons, Inc., Borger, Tex.
[0044] The furnace black is "N-774 Furnace Carbon Black"
commercially available from Engineered Carbons, Inc., Borger,
Tex.
[0045] Silicon metal is a -200 mesh (0.075 millimeter) silicon
powder commercially available from Globe Metallurgical, Inc,
Beverly, Ohio.
[0046] Sodium tripolyphosphate is a dispersant commercially
available under the trade name "HYSORB" technical grade from FMC
Corporation, Bedford Park, Ill.
[0047] Daxad 11 is an anionic dispersant that is a sodium salt of a
polymerized alkyl naphthalene sulfonic acid commercially available
from W. R. Grace & Co., Lexington, Mass.
[0048] Marasperse CBA-1 is a dispersant that is a modified lignin
comprising a desulphonated sodium lignosulfonate commercially
available from LignoTech USA, Bridgewater, N.J.
[0049] Vinyon Fiber is a fibrous material of vinyl acetate and
vinyl chloride fibers commercially available from Waker, USA,
Norwalk, Conn.
EXAMPLES 1 TO 5
[0050] Five high alumina, ultralow cement refractory castable
compositions are set forth in Table I below. Example 1 is a
standard refractory castable composition mix as known by those
skilled in the art employing microsilica and Reactive Aluminas as
the ultrafine refractory material and sodium tripolyphosphate as
the dispersant. Example 2 sets forth a refractory castable
composition for comparison purposes wherein sodium tripolyphosphate
is the dispersant and thermal black and Reactive Aluminas are the
ultrafine refractory material. Examples 3, 4, and 5 set forth
various mix formulations of the refractory castable compositions of
this invention employing thermal black and Reactive Aluminas as the
ultrafine refractory material and a dispersant other than sodium
tripolyphosphate.
[0051] Table I sets forth the mix formulations for Examples 1-5,
and the casting characteristics, physical properties after drying
at 230.degree. F. (Fahrenheit) and after coking at 2000.degree. F.,
along with high temperature strength testing.
[0052] The flow diameter test set forth in Tables I, II and III is
performed on a small vibrating table. A 1/2-pound ball of wet mix
of the formulation of each example is placed on the table and
vibrated for 15 seconds at a set frequency. After vibration, the
diameter of the slumped ball is measured and recorded.
[0053] The results set forth in Table I show that by substituting
thermal black for microsilica in a refractory castable composition,
the casting characteristics can be significantly improved using the
same or similar water content. Example 1 is a conventional ultralow
cement refractory castable composition, well known by those skilled
in the art, containing 5 weight percent microsilica and 10 weight
percent Reactive Aluminas as the ultrafine refractory materials and
sodium tripolyphosphate as the dispersant. This example had fair
flow characteristics and satisfactory physical properties. Example
2 sets forth a comparative composition wherein thermal black is
employed as the ultrafine refractory material in place of
microsilica, and wherein the same sodium tripolyphosphate
dispersant is used as in Example 1. It will be appreciated by those
skilled in the art that Example 2 has poor to no flow and
significantly inferior physical properties compared with those for
Example 1. Examples 3 and 4 set forth the present invention wherein
thermal black is employed as the ultrafine refractory material in
place of microsilica, but dispersants specifically designed to
disperse thermal black in an aqueous solution are used in place of
sodium tripolyphosphate. The casting characteristics for the
castable composition of Examples 3 and 4 are good to very good, and
the density and porosity values are similar to those of Example 1,
indicating good material flow and compaction. The high temperature
strengths of the compositions of this invention, Examples 3 and 4,
containing thermal black are less than those for the mix of Example
1 containing conventional microsilica as the ultrafine refractory
material. This is due to the inert, non-reactive nature of the
thermal black when used in combination with a calcium aluminate
cement in the bonding matrices of the compositions. This is
partially overcome by the addition of metals to the mix of Example
5 of the present invention that results in the formation of
carbides at temperatures beginning at about 1470.degree. F.
(Fahrenheit) which strengthens the bonding matrix. The use of a
metal(s) addition can also provide for improved oxidation
resistance, which is important when carbon-containing mixes are
used in oxidizing atmospheres.
1 TABLE I Example Number: 1 2 3 4 5 Wt. % Wt. % Wt. % Wt. % Wt. %
Mix Formulations: Tabular Alumina 83.5 83.5 83.5 83.5 80.5 (-3 mesh
and finer) Reactive Alumina 5.0 5.0 5.0 5.0 5.0 (0.4 micron)
A-1000SGD Reactive Alumina 5.0 5.0 5.0 5.0 5.0 (3.0 micron)
A-3000-FL Calcium Aluminate 1.5 1.5 1.5 1.5 1.5 Cement Microsilica
5.0 -- -- -- -- Thermax Floform N-990 -- 5.0 5.0 5.0 5.0 Thermal
Black (Cancarb Limited) Silicon Metal -- -- -- -- 3.0 (-200 mesh)
Plus Additions: Sodium 0.2 0.2 -- -- -- Tripolyphosphate Daxad 11
Dispersant -- -- 0.2 -- -- Marasperse CBA-1 -- -- -- 0.2 0.2
Dispersant Water for Casting: 4.5 7.5 4.5 4.5 4.5 Casting
Characteristics Flow Diameter, inches 2.9 2.25 3.6 4.1 4.3 Comments
Fair Poor Good Very Very to No Good Good Flow After Drying
230.degree. F. Density from Porosity, 195 176 196 197 193 pcf
Apparent Porosity, % 15.0 22.2 13.5 13.3 13.6 After Coking at
2000.degree. F. Density from Porosity, 197 175 195 196 194 pcf
Apparent Porosity, % 15.3 23.8 15.6 14.8 14.0 At 2800.degree. F.
830 -- 410 460 590 (Reducing Atmosphere) Crushing Strength, psi
EXAMPLES 6 TO 9
[0054] Table II sets forth the mix formulations for Examples 6-9.
Examples 6-8 are refractory castable compositions of the present
invention wherein the ultrafine refractory material is 10 weight
percent Reactive Aluminas and 5 weight percent N990 thermal black
and the binder is a powdered novolak resin. The powdered novolak
resin employed in Table II is commercially available under the
trade name Durite RD 763 A from Borden Chemical, Inc., Louisville,
Ky. As shown in Table II, the refractory castable compositions of
the present invention, Examples 6-8, employing thermal black as a
portion of the ultrafine refractory material resulted in very good
flow properties. Examples 7 and 8 illustrate that additions of fine
silicon metal to the resin bonded compositions resulted in improved
high temperature strength.
[0055] Example 9 illustrates a refractory castable composition of
the present invention which contains thermal black and reactive
alumina as the ultrafine refractory material and powdered novolak
resin (as described herein) and calcium aluminate cement as the
binders. Example 9 shows that the mix formulation resulted in very
good flow properties and physical characteristics.
2 TABLE II Example Number: 6 7 8 9 Wt. % Wt. % Wt. % Wt. % Mix
Formulations: Tabular Alumina 82.0% 79.0% 77.0% 79.0% (-3 mesh and
finer) Reactive Alumina 5.0 5.0 5.0 5.0 (0.4 micron) Reactive
Alumina 5.0 5.0 5.0 5.0 (3.0 micron) Calcium Aluminate Cement -- --
-- 1.0 Powdered Novolak Resin 3.0 3.0 3.0 2.0 Thermax Floform N-990
5.0 5.0 5.0 5.0 Thermal Black (Cancarb Limited) Silicon Metal --
3.0 5.0 3.0 (-200 mesh) Plus Additions: Marasperse CBA-1 0.2% 0.2%
0.2% 0.2% Dispersant % Water for Casting: 4.5 4.5 4.5 4.5 Casting
Characteristics Flow Diameter, inches 4.0 4.0 4.2 4.1 Comments Very
Very Very Very Good Good Good Good After Drying 350.degree. F.
Density from Porosity, 186 184 181 183 pcf Apparent Porosity, %
12.7 13.2 13.6 15.2 After Coking at 2000.degree. F. Density from
Porosity, 185 181 180 184 pcf Apparent Porosity, % 18.5 17.2 16.5
17.0 At 2800.degree. F. 950 2000 3630 790 (Reducing Atmosphere)
Crushing Strength, psi
EXAMPLES 10 AND 13
[0056] In Table III, Examples 10, 11 and 13 set forth additional
examples of the mix formulations of the present invention. The mix
formulation of Example 12 is set forth for comparison purposes.
Examples 10 and 11 set forth mix formulations in which two
different commercially available N-990 thermal blacks,
respectively, are evaluated in the refractory castable compositions
of the instant invention. Examples 10 and 11 contain N-990 type
(ASTM) thermal carbon blacks which have an average particle size of
about 0.3 micron. Example 10 contains an N-990 thermal black
commercially available from Cancarb Limited, Medicine Hat, Alberta,
Canada and Example 11 contains an N-990 thermal black commercially
available from Engineered Carbons, Inc., Borger, Tex.
[0057] Example 12 sets forth a comparative mix formulation which
contains an N-774 type (ASTM) furnace carbon black having an
average particle size of 0.05 micron, commercially available from
Engineered Carbons, Inc., Borger, Tex.
[0058] Example 13 sets forth a mix formulation of the present
invention wherein all of the ultrafine refractory material
comprises thermal black. Examples 10-13 each employ a fiber
addition of polypropylene fiber commercially available under the
trade name "HERCULON" non-woven staple fibers (Denier=3.0,
Length=5.0 mm), commercially available from Hercules Incorporated,
Wilmington, Del.
[0059] As shown by the results set forth in Table III, Examples 10
and 11, mix formulations containing the two N-990 thermal blacks,
respectively, provide the same casting characteristics at the same
water contents. The resulting physical properties are very similar
for the mix formulation of Examples 10 and 11.
[0060] The comparative mix formulation of Example 11 containing the
furnace carbon black required more water and dispersant to achieve
a good flow, which resulted in inferior physical properties (i.e.
apparent porosity, 18.5% after drying at 230.degree. F., and 20.4%
after coking at 2000.degree. F.) compared to those mix formulations
of Examples 10, 11, and 13 wherein all or a portion of the
ultrafine refractory material comprises thermal black.
3 TABLE III Example Number: 10 11 12 13 Wt. % Wt. % Wt. % Wt. % Mix
Formulations: Tabular Alumina 83.5 83.5 83.5 83.5 (-3 mesh and
finer) Reactive Alumina 5.0 5.0 5.0 -- (0.4 micron) Reactive
Alumina 5.0 5.0 5.0 -- (3.0 micron) Calcium Aluminate Cement 1.5
1.5 1.5 1.5 Thermax Floform N-990 5.0 -- -- 15.0 Thermal Black
(Cancarb Limited) N-990 Thermal Carbon Black -- 5.0 -- --
(Engineered Carbons, Inc.) N-774 Furnace Carbon Black -- -- 5.0 --
(Engineered Carbons, Inc.) Plus Additions: Marasperse CBA-1 0.2 0.2
0.5 0.5 Dispersant Polypropylene-Based Fibers 0.15 0.15 0.15 0.15 %
Water for Casting: 4.5 4.5 5.5 5.5 Casting Characteristics Flow
Diameter, inches 3.75 3.75 3.50 4.0 Comments Good Good Good Very
Good After Drying 230.degree. F. Density from Porosity, 198 197 183
173 pcf Apparent Porosity, % 12.5 12.9 18.5 15.9 After Coking at
2000.degree. F. Density from Porosity, 195 194 183 172 pcf Apparent
Porosity, % 15.3 15.7 20.4 18.5
[0061] The mixes shown in Tables I, II, and III had the following
screen analysis:
4 % Held on 4 mesh (Tyler) 13 .+-. 5 % Held on 10 mesh 40 .+-. 6 %
Pass 10 mesh, Held on 28 mesh 12 % Pass 28 mesh, Held on 65 mesh 10
% Pass 65 mesh 38 .+-. 6 % Pass 150 mesh 32 .+-. 6 % Pass 325 mesh
29 .+-. 5
EXAMPLE 14
[0062] Example 14 sets forth an example of employing a thermal
black and reactive alumina as the ultrafine refractory material in
a non-slumping, high density, low moisture sprayable, pumpable
refractory castable composition of the instant invention that can
be applied without forms. In Example 14, the flocculating agent was
added at the time of installation in an amount sufficient to give a
bulk density of at least 110 pcf. The flocculating agent in Example
14 was employed in an amount of about 0.4 weight percent of a
thirty-two percent calcium chloride solution. The purpose of this
flocculating agent is to "over-power" or eliminate the effect of
the dispersant in making the tempered castable. The flocculating
agent acts to turn the low moisture castable instantly into a
viscous plastic mass, making it sticky enough at its existing low
water level to be sprayed onto a surface without slumping and
without the need for forms. The flocculating agent reacts with all
of the refractory castable composition components causing them to
agglomerate.
[0063] In Example 14, water is added in an amount sufficient to
achieve a pumpable consistency suitable for use with pump means and
the associated hose means and nozzle means utilized therewith. Such
pump means, hose means and nozzle means are conventional and well
known by those skilled in the art. For example, the nozzle means
may have an air line hookup where air is fed to the nozzle means in
order to take the pumpable refractory castable composition into a
form such that it is sprayed onto a surface to be lined with the
sprayable refractory castable composition. Preferably, the
flocculating agent is added through the air line associated with
the nozzle means and is admixed with the tempered pumpable first
component of the sprayable refractory castable composition just as
it is sprayed onto a surface, such as for example, the surface of a
metallurgical vessel. If desired, the flocculating agent can be
added by means of any conventional pump and a "Y" interconnect to
the air line, so that the flocculating agent can be added at the
proper rate directly to the refractory castable composition at the
nozzle.
[0064] It will be appreciate by those skilled in the art that while
Example 14 discloses adding the flocculating agent to the
refractory castable composition at the nozzle means, the
flocculating agent may be added upstream of the nozzle means, such
as for example, through the hose means at or just prior to
installation of the sprayable refractory castable composition.
[0065] The amount of flocculating agent is critical since it can
adversely affect the desired bulk density of the castable. Bulk
density is considered the most important physical property for a
refractory castable, in that all other important properties such as
strength is directly proportional to the density of any given
castable composition. Thus, as density decreases, strength also
decreases. With the castables of the present invention, the bulk
density should be at least 110 pcf (pounds per cubic foot,
lbs./ft.sup.3), and preferably greater than 130 pcf. The amount of
flocculating agent added, as described herein, must therefore be
carefully controlled.
[0066] As will be appreciated and known by those skilled in the
art, another pump means for feeding the flocculating agent to the
nozzle means or hose means must have the capacity to match the pump
means for pumping the refractory castable composition at its given
material output, and must be able to generate enough pressure to
overcome the air pressure in the line, which is ordinarily about 50
to 100 psi (pounds per square inch).
[0067] With respect to the amount of water added in order to have
the satisfactory tempered mix; that is, to have an adequate pump
cast consistency, the amount will vary, dependent mainly upon the
particular components in the mix, the particular pump means
utilized, the length of hose means by which it is supplied, and the
air pressure. These are all readily calculable by those skilled in
this art. The amount of water added to properly temper the
refractory castable composition to obtain a proper pump cast
consistency, is such that it could be run through pump means, and
through about 25 to 200 feet of hose means, and placed on a surface
utilizing about 80 psi (pounds per square inch) air pressure.
[0068] In Example 14, an Allentown Powercreter Pro swing valve
piston pump and a 500 psi diaphragm chemical pump to move the
flocculating agent were used. A 350-cfm (cubic feet per minute) air
compressor was used as the source of air feed and air was injected
into the nozzle at 90 psi pressure. The sprayable refractory
castable composition was tested by spraying the material onto a
vertical surface, then cutting the sprayed panel on a diamond saw
into the desired test speciments after curing.
[0069] In Example 14, the Calcined Chinese Bauxite is approximately
an 85 to 90 weight % alumina grain from China commercially
available through F & S International, New York, N.Y., which is
crushed and ground into the desired screen fractions. The Dead
Burned Magnesia is approximately a 98 weight % magnesia grain such
as H-W 98 Magnesite commercially available from Harbison-Walker
Refractories Company, Pittsburgh, Pa., which is crushed and ground
into the desired screen fractions. The sulfur powder is sulfur
powder commercially available from Rhone-Poulenc Basic Chemicals
Co., Shelton, Conn. The citric acid is citric acid, Anhydrous, FCC,
USP, commercially available from Haarmann & Reimer Corp.,
Elkhart, Ind. The fiber addition is polypropylene fiber
commercially available under the trade name "Herculon" non-woven
staple fibers (Denier=3.0, Length=5.0 mm) commercially available
from Hercules Incorporated, Wilmington, Del.
5 Example Number: 14 Weight % Mix: Calcined Chinese Bauxite (-4
mesh and 75 finer) Dead Burned Magnesia (-10 mesh and 6 finer)
Reactive Alumina (0.4 micron) 5.0 Reactive Alumina (3.0 micron) 5.0
Calcium Aluminate Cement 3 Thermax Floform N-990 Thermal Black 5
(Cancarb Limited) Silicon Metal, -200 mesh 3 Powdered Novolak Resin
2 Plus Additions: Marasperse CBA-1 Dispersant 0.1 Sulfur Powder 0.1
Citric Acid 0.03 Polypropylene-Based Fibers 0.1 Water to Achieve a
Pump Cast 8.0 Consistency Application Rate and Test Results
Refractory Composition Pump Feed Rate: 300 lbs/min. (pounds/minute)
Flocculant Pump Feed Rate: 0.2 Gal/min. (gallons/minute) Bulk
Density, pcf 154 After Drying at 350.degree. F.: Cold Crushing
Strength, psi 4080 After Drying at 350.degree. F.:
[0070] In Example 14, thermal black was used in conjunction with
silicon metal and powdered novolak resin in a bauxite-based,
ultralow cement (<1.0 wt. % CaO) castable. Dead burned magnesia
was added to this composition to form magnesium aluminate spinel in
situ at elevated temperatures. The combination of thermal black and
magnesium aluminate spinel in an alumina-based composition provides
improved corrosion resistance to metallurgical slags.
[0071] Sulfur powder is added to help prevent hydration of the
magnesia; citric acid is added to extend the working time of the
castable; and polypropylene-based fibers were added to facilitate
moisture removal upon heat up of the material. These additives are
known by those skilled in the art and are used in conventional
amounts. This example demonstrates that a non-slumping, pumpable,
sprayable refractory castable composition containing thermal black
and Reactive Aluminas as the ultrafine refractory material can be
applied using the installation method as described herein resulting
in a sprayable refractory castable product having good density and
strength.
[0072] Whereas particular embodiments of the instant invention have
been described for the purposes of illustration, it will be
evidence to those persons skilled in the art that numerous
variations and details of the instant invention may be made without
departing from the instant invention as defined in the appended
claims.
* * * * *