Note: Descriptions are shown in the official language in which they were submitted.
2152683
h~lnO~ OF LINING A BLAST F~RNACE
FIELD OF THE l~v~NllON
This invention relates to a method and
structure for lining blast furnaces and other
metallurgical vessels used in the iron and steel
industry, with a refractory lining.
BAC~GRO~ND OF THE lN V~N llON
Blast furnaces are used in the iron and steel
industry for the production of pig iron which is later
converted into steel and/or cast into a suitable form.
The blast furnaces typically have refractory linings
which protect their steel walls from oxidation,
corrosion and erosion which would otherwise result from
exposure to molten metal in the blast furnace.
However, the refractory linings themselves experience
wear and tear from exposure to the molten metal, and
periodically have to be repaired or replaced.
The lining, or relining, of blast furnace
interiors with a refractory has conventionally been a
time-consuming, labor-intensive, and relatively
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expensive process. Conventional lining methods have
involved the use of preformed refractory bricks of
predetermined size and shape which are adapted to
conform to the contour of the blast furnace walls when
the bricks are assembled together and stacked inside
the blast furnace. The bricklaying methods have
evolved into a complex science involving the selection
of bricks of different sizes, shapes and compositions,
for different regions in a blast furnace, and for
different blast furnaces. Once the proper refractory
bricks have been selected and formed, the bricks are
laid side-by-side, and stacked vertically, in the blast
furnace, and the joints between the bricks are filled
with a refractory grout or slurry which then hardens
and holds the bricks together.
U.S. Patent 3,672,649, issued to Allen,
describes a departure from the use of conventional
bricks. A plurality of molding rings are installed, in
sequence, in the blast furnace at a selected distance
from the blast furnace steel wall. After the first
ring is installed, a refractory lining material is
manually poured between the steel wall and the molding
ring, or is gunned into place~ Then, a molding rings
is placed at the next higher level in the blast
furnace, and the above process is repeated until a
monolithic refractory lining completely covers the
desired region inside the blast furnace.
Unfortunately, manual pouring and gunning are
also very labor-intensive and require much time to
complete. Although a monolithic refractory is
ultimately formed, eliminating the need for preformed
refractory bricks, the number of stages required to
complete the mAnl~l pouring or gunning process is quite
large. In the above-identified U.S. Patent 3,672,649,
no less than ten stages (represented by ten stacked
molding rings) are shown in the drawings to form only a
21a2~83
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part of the desired monolithic refractory lining. As a
result, the use of refractory bricks is still common
notwithstanding the availability of this alternative
process.
SUMMARY OF THE INVENTION
The present invention is a method of lining a
blast furnace in stages, with a monolithic refractory
lining, which requires much less time, labor and
expense than prior art refractory lining methods. A
refractory casting composition especially adapted for
transporting using a concrete pump or other pump is
provided. The pumpable casting composition eliminates
the need for manual pouring and/or gunning.
A first inner form member preferably
constructed from a rigid frame and a porous consumable
material, is installed at the lower end of the blast
furnace region which is being lined. The inner form
member is positioned at a selected distance from the
blast furnace shell or wall, so that the space between
the form member and the shell or wall acts as a mold.
Next, the section of the blast furnace shell
lateral to the form member may be lined with a thin
refractory board, and the rPm~;n;ng space between the
refractory board and form member is filled with the
pumpable casting composition. The pumpable casting
composition is permitted to harden and set, to form a
first (lower) section of the refractory lining.
Next, a second inner form member is
positioned above the first inner form member in the
blast furnace. The section of the blast furnace shell
adjacent the second inner form member may be lined with
thin refractory board, and the remaining space between
the refractory board and second inner form mem~ber is
filled with the pumpable casting composition. The
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pumpable casting composition is permitted to harden and
set, to form a second section of the refractory lining.
The above process is repeated until an entire
monolithic refractory lining has been formed. One
advantage of using a pumpable casting composition is
that the number of required stages is dramatically
reduced by the removal of manual operator constraints
associated with manual pouring or gunning. Also, the
use of a porous consumable form facilitates the use of
larger stages because water in the refractory can be
expelled through the consumable form in addition to
evaporating in a vertical direction. Each single stage
(represented by a single form member) can now be made
taller, and can even be taller than the height of a
man.
A second advantage is that the labor-
intensiveness of manual pouring or gunning is reduced
and simplified by the use of a pump to transport the
casting composition. The result is an economical
process that provides a significant time-saving, labor-
saving and cost-saving incentive to steer away from the
prior art use of refractory bricks, and from monolithic
linings installed by manual pouring or gunning.
With the foregoing in mind, it is a feature
and advantage of the invention to provide a method of
installing a refractory lining in a metallurgical
vessel which substantially reduces the time, labor and
expense associated with prior art methods.
It is also a feature and advantage of the
invention to provide a method of installing a
refractory lining in a metallurgical vessel which
results in the formation of a high strength, high
quality, monolithic refractory lining.
The foregoing and other features and
advantages of the invention will become further
apparent from the following detailed description of the
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presently preferred embodiments, read in conjunction
with the accompanying drawings. The detailed
description and drawings are intended to be merely
illustrative rather than limiting, the scope of the
invention being defined by the appended claims and
equivalents thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional schematic view of a
blast furnace during the first (lowermost) stage of
formation of a refractory lining according to the
method of the invention.
FIG. 2 shows the blast furnace of FIG. 1
during the second stage of formation of the refractory
lining.
FIG. 3 shows the blast furnace of FIGS. 1 and
2 after the entire refractory lining has been formed in
six stages.
FIG. 4 shows the blast furnace of FIG. 3
after the rigid frames of the form members have been
removed.
FIG. 5 i~ a top view of a form member used in
the method of the invention.
FIG. 6 is a sectional view of the form member
shown in FIG. 5.
FIGS. 7-12 are front views illustrating
sections which can be used to construct consumable
forms for the various stages of the method of the
invention.
DE~TTT~n DESCRIPTION OF THE
PRESENT~Y PREFERRED EMBODIMENTS
Referring to FIG. 1, blast furnace 10
includes a vertical stack portion 12 superimposed over
a bosh portion 13 which, in turn, is superimposed over
a lower hearth portion 14; and a bell or dome
portion 16 above the stack. While the method of the
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invention can be used to line any portion of the blast
furnace 10 or other metal containment device, the
invention is herein illustrated with reference to the
stack portion 12. Thus, in FIG. 1, the hearth
portion 14 includes an upper hearth 15 which is lined
with a layer 17 of conventional refractory bricks and a
lower hearth 18 which typically is completely filled
with conventional refractory bricks (not shown).
Similarly, the bosh 13 above the hearth is lined with a
layer 19 of conventional refractory bricks. The entire
blast furnace 10 is also contained by an outer steel
shell 20 which is adjacent to, and houses, the
refractory liners.
The stack portion 12 is lined one stage at a
time, in accordance with the invention. Initially, a
layer 22 of refractory insulating board can be mounted
against the steel shell 20 in the first (lowest)
stage 50 of the stack 12~ The insulating board
layer 22 is optional yet preferred, because it helps
contain the heat inside the blast furnace. The
insulating board layer may not be needed in situations
where the main refractory lining to be formed is thick
enough, or possesses sufficient insulating properties,
to overcome the need for a separate insulating board
layer 22.
When used, the insulating board layer 22 is
preferably constructed of magnesium silicate or alumina
silicate board, and preferably has a thickness of about
one to three inches, most preferably about two inches.
One commercially available insulating board material
which is suitable for use as the layer 22 is alumina
silicate board, available from Pabco Company, located
in Alliance, Ohio. Other conventional insulating
boards may also be used. The insulating board layer 22
can be mounted against the steel shell 20 using
conventional techniques, such as by applying refractory
21~2683
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mortar to the boards and the shell, or by using
fastening pins to join the boards and shell together.
After the insulating board layer ~2 has been
installed in the first stage 50 of the stack 12, the
next step is to assemble and install a first form
member 62 in the first stage 50 at a distance from the
steel shell 20 and insulating board layer 22. The
first form member 62, shown in detail in FIGS. 5 and 6,
includes a rigid frame 30 and a cylindrical or frustro-
conical porous consumable form 48 laterally adjacent
the frame 30, around the frame 30, and connected to the
frame 30 usi'ng plastic or metal wires or straps, or
another suitable fastening mechanism (not shown).
As shown in FIGS . 5 and 6, the rigid frame 30
includes an upright center pole 32, a plurality of
spokes 34 projecting radially outward from the center
pole 32, and a plurality of concave plates 36 at the
outer ends of the spokes 34 which are used for
supporting and mounting the consumable form 48. As
shown in FIG. 6, the spokes 34 include upper spokes 38
projecting outward from about the top of the center
pole 32, middle spokes 40 projecting outward from about
the middle of the center pole 32l and lower spokes 42
projecting outward from about the bottom of the center
pole 32. The spokes 34 include telescoping adjustment
mechanisms 44 which are used to adjust the lengths of
the spokes. By selectively adjusting the lengths of
the various spokes, the form number 62 can be adjusted
to wider or narrow diameters, and can be made to have a
cylindrical, frustro-conical, or inverted frustro-
conical configuration.
The rigid frame 30 is preferably constructed
from beams and/or tubes made from steel, Re-Bar, or
another rigid metal. Surrounding the rigid frame 30,
in the radial direction, is the consumable form 48
which, preferably, is constructed from a consumable
7 ~ 5~3
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porous material in order to facilitate drying of the
refractory lining which is being installed. The
consumable porous material may be an open-mesh screen
made from plastic or metal, or may be constructed from
paper, plastic foam, or another material which
facilitates the transmission and evaporation of
moisture. One suitable porous metal screen material is
sold under the name "Stay-Form" by the Alabama Metal
Industries Corp. of Birmingham, Alabama.
The consumable form 48 is mounted to the
rigid frame 30 at the concave plates 36. Connection of
the consumable form 48 to the plates 36 may be
accomplished using metal or plastic tie-wires or strap,
string, glue, rivets, or any suitable fastening
mechanism. The form member 62 can be constructed
in situ in the blast furnace 10, or can be constructed
externally and inserted into the blast furnace 10.
Platforms, cables, and elevators may be temporarily
provided in the blast furnace, as needed, to facilitate
construction and/or installation of the first form
member 62 and the other form members discussed below.
The form member 62 should be constructed and
installed so that there is a space corresponding to the
thickness of the refractory lining to be formed,
between the outer surface of the porous consumable
form 48 and the inner surface of the insulating
boards 22 (if used) or the steel shell 20 (if no
insulating boards are used). Next, a pumpable casting
composition 80 is injected using feed pipes 82 and 84
connected via a common material hose 83 to a pump 86,
from a source 88 to the space between the consumable
form 48 and the insulating boards 22 or steel shell 20.
The pumpable casting composition 80 is then allowed to
harden and set for about 5-10 hours before the second
stage of the installation is initiated. This hardening
readily occurs as much of the liquid carrier (i.e.,
* Trademark
~ t ~
_
g
water) is transmitted (i.e. expelled or evaporated)
through the porous consumable form.
Suitable pumpable refractory casting
compositions are disclosed in U.S. Patent 5,147,830.
Generally, these pumpable compositions include about
55-90% by weight of a granular refractory base material
selected from calcined clay, mullite, brown fused
alumina, tubular alumina and mixtures thereof; about 8-
14~ by weight liquid carrier, which later serves as a
binder after drying, including a dispersion of about
15-70% by weight colloidal silica in water; optionally,
about 5-20~ by weight calcined alumina and/or 1-35% by
weight silicon carbide; and, preferably, about 0.2-1.0%
by weight of a setting agent such as calcium aluminate
cement or magnesium oxide, and about 1-10% by weight
microsilica.
The refractory material 80 may be installed
using a concrete pump or similar pump as described in
U.S. Patent 5,147,830. One example of a useful
concrete pump is the Thom-Kat TVS16-2065, available
from Pultzmeister, Inc., Thomsen Div., Gardena, CA
90248. Such a concrete pump is described in U.S.
Patent No. 3,382,907, and in German Patent
No. 2,162,406.
Other commercially available concrete pumps,
and other suitable pumps, can also be used to transport
the casting composition 80. One presently preferred
pump is the Putzmeister pump, available from Original
Concrete, located in Bensenville, Illinois.
After the refractory material 80 has suffi-
ciently hardened, a second inner form member 64 is
installed above the first inner form member 62 as shown
in FIG. 2, in the second stage 52 of the stack 12, at
the next higher level. The second inner form member 64
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may be constructed in exactly the same way as the form
member 62 except for some variation in ~;m~n~ions due
to the changing diameter of the steel shell 20. After
the second form member 64 is installed, refractory
insulating boards 24 may, if used, be installed
adjacent the steel shell 20 and above the insulating
boards 22. Then, a further quantity of the casting
composition 80 is pumped into the space between the
form member 64 and the insulating boards 24 (if used)
or the shell 20 (if no insulating boards are used).
The refractory material 80 is again permitted to harden
for about 4-10 hours, depending on the thickness of the
liner, before proceeding to the third stage of the
installation.
The above procedure is repeated, as shown in
FIG. 3, sequentially for six stages, until the entire
stack 12 is lined with the pumpable refractory
material 80. Form members 66, 68, 70, 72 are
installed, respectively, in the third stage 54, the
fourth stage 56, the fifth stage 58, and the sixth
stage 60 of the installation. After each form member
is installed, refractory insulating boards (26, 27, 28
or 29) may be installed in the respective stage
adjacent the steel shell 20. Then, the pumpable
casting composition 80 is installed between each form
member and the respective insulating boards or
shell 20, and is permitted to harden before the next
stage of installation is commenced.
The feed pipes 82 and 84 are raised in the
stack 12, as needed, for each stage of injection of the
pumpable casting composition 80. This raising of the
feed pipes may be accomplished, for example, by raising
a hoist cable 85 connected to the feed pipes, or by
mounting the feed pipes on an adjustable platform (not
shown). One significant advantage of using a pumpable
casting composition is that only the feed pipes 82 and
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84 need to be raised, while the pump 86 and source 88
remain conveniently on the ground, and outside of the
blast furnace 10. The material hose 83 that leads to
the feed pipes 82 and 84 can be conveniently inserted
into the blast furnace 10 through the tuyere opening 81
located in the side, and near the bottom, of the blast
furnace.
The use of a porous consumable form 48
facilitates drying and hardening of the casting com-
position 80 after each stage of installation. The use
of a pumpable casting composition 80 eliminates the
need for a labor-intensive gunning or pouring operation
at each stage. These two factors, in combination,
greatly simplify the formation of the refractory liner
by reducing the number of stages that are required.
Unlike the prior art, the height of each stage is not
limited by the height of a man doing manual labor, or
by the height of wet refractory composition that can be
dried from the top. Instead~ the only limiting factor
as to the height of each stage is the inward pressure
exerted by the wet casting composition on the
consumable form 48 of each respective form member.
By using the method of the invention, it
becomes possible to line a blast furnace stack portion
having a height of 50 feet using no more than about
eight stages of installation, and preferably no more
than about six stages of installation. To ensure
efficient practice of the method of the invention, the
average height of each stage (and each corresponding
form member) should be at least about six feet,
preferably at least about eight feet. By using six
stages of about 100 inches each, a 50-foot stack can be
completely lined in less than six days total labor
time. This compares to labor times of several weeks
when conventional lining techniques are used.
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After the entire refractory lining 80 is
formed and hardened, the rigid frames 30 of the form
members 62, 64, 66, 68, 70 and 72 can be detached and
removed, leaving only the consumable fonms 48 in place
as shown in FIG. 4. Then, the refractory lining 80 can
be baked at an elevated temperature (above 250~F) for
about 5-30 hours, depending on its thickness, to ensure
complete setting and drying. The consumable form 48 is
burned off (i.e. "consumed") either during baking of
the refractory lining 80 or, more likely, during
subsequent exposure to molten metal when the blast
furnace 10 is put to use.
FIGS. 7-12 illustrate a presently preferred
method and material for constructing the consumable
forms 48 for the form members 62, 64, 66, 68, 70 and
72. This method and material are described for a blast
furnace having a stack portion 12 height of about 50
feet, a stack portion 12 inner diameter (after lining)
of about 23-25 feet, and a stack portion 12 geometry as
shown in FIGS. 1-4.
Referring to FIG. 7, the consumable form 48
for the first (lowest) form member 62 is constructed
from porous members 100 and 102, each of which is
constructed from a flexible porous metal screen 104
supported by metal braces 106~ The consumable porous
members 100 and 102, which may be of a commercially
available material known as Re-Bar, are placed edge to
edge and joined together using thin metal tie wires,
plastic bands, or another suitable connecting means.
The first form member 102 includes nineteen sections of
the "standard" porous member 100, and one section of
the "key" porous member 102, joined edge to edge to
provide the consumable form 48 (FIG. 5). As indicated
above, the porous members 100 and 102 of the consumable
form 48 may also be joined to the plates 36 of the
rigid frame 30 (FIG. 5).
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As shown in FIG. 7, each of the nineteen
standard porous members 100 has a width of 44 inches at
its smaller end 101, a width of 48 inches at its larger
end 103, and a height of 102 inches along its
edges 105. The key porous member 102 has a width of 35
inches at its smaller end 107, a width of 36 inches at
its larger end 108, and a height of 102 inches at its
edges 109. The height of 102 inches for the porous
members 100 and 102 is also the height of the first
stage 50 and the first inner form member 62 (FIG. 1).
The flexible porous metal screen 104 prefer-
ably has an opening size of about 0.125 inch. Gener-
ally, the screen openings should not be so small as to
inhibit the transmission and evaporation of water from
the refractory material 80, but should not be so large
that the granular components of the refractory materia
80 pass through the screen.
FIG. 8 illustrates the porous members 110 and
112 which can be used to construct the consumable
form 48 for the second form member 64 used in the
second stage 52 of the refractory lining installation
(FIG. 2). The material used to construct the porous
members 110 and 112 is the same as described above with
respect to FIG. 7, but the ~;men~ions are different.
The consumable form 48 used in the second stage 52
includes nineteen sections of 'lst~n~rdll porous
members 110 and one section of the "key" form
member 112, aligned edge to edge and joined together.
Each standard porous member 110 has a width of 45
inches at its smaller end 111, a width of 48 inches at
its larger end 113, and a height of 99.75 inches along
its edges 115. The key porous member 112 has a width
of 36.875 inches at its smaller end 117, a width of 54
inches at its larger end 118, and a height of 99.75
inches along its edges 119.
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FIG. 9 illustrates the porous members 120 and
122 which can be used to construct the consumable
form 48 for the third form member 66 used in the third
stage 54 of the installation (FIG. 3). In FIG. 9, the
standard porous member 120 is identical in every
respect to the standard porous member 110 in FIG. 8.
However, only eighteen sections of standard porous
members 120 are used to construct the consumable form
of the third form member 66. The third form member 66
also includes one key porous member 122 having a width
of 45 inches at its smaller end 127, a width of 59.75
inches at its larger end 128, and a height of 99.75
inches along its edges 129.
FIG. 10 illustrates the porous members 130
and 132 which can be used to construct the consumable
form 48 for the fourth form member 68 used in the
fourth stage 56 of the installation (FIG. 3). In
FIG. 10, the standard porous member 130 is identical in
every respect to the st~n~rd porous member 110 in FIG.
8. However, only seventeen sections of standard porous
members 130 are used to construct the consumable form
of the fourth form member 68. The consumable form of
the fourth form member also includes one key porous
member 132 having a width of 53.75 inches at its
smaller end 137, a width of 65.5 inches at its larger
end 138, and a height of 99.75 inches along its
edges 139~
FIG. 11 illustrates the porous members 140
and 142 which can be used to construct the consumable
form 48 for the fifth form member 70 used in the fifth
stage 58 of the installation (FIG. 3). In FIG. 11, the
standard porous member 140 is identical in every
respect to the standard porous member 110 in FIG. 8.
However, only sixteen sections of st~n~rd porous
members 140 are used to construct the consumable form
of the fifth form member 70. The fifth form member 70
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also includes one key porous member 142 having a width
of 62.5 inches at its smaller end 147, a width of 71.25
inches at its larger end 148, and a height of 99.75
inches along its edges 149. As with every stage of the
installation, the consumable form 48 is constructed by
aligning the many stan~rd porous members and the one
key porous member edge to edge and joining them
together to form a complete enclosure (FIG. 5).
FIG. 12 illustrates the porous members 150
and 152 which can be used to construct the consumable
form 48 for the sixth form member 72 used in the sixth
stage 60 of the installation (FIG. 3). The consumable
form 48 for the sixth stage 60 includes fifteen
sections of standard porous members 150 and one section
of the key porous member 152, aligned edge-to-edge and
joined together. Each standard porous member 150 has a
width of 45 inches at its smaller end 151, a width of
48 inches at its larger end 153, and a height of 102
inches along its edges 155. The key porous member 152
has a width of 25 inches at its smaller end 157, a
width of 71.25 inches at its larger end 158, and a
height of 102 inches along its edges 159.
While the embodiments of the invention
disclosed herein are presently considered to be
preferred, various modifications and improvements can
be made without departing from the spirit and scope of
the invention. The scope of the invention is indicated
in the appended claims, and all charges that fall
within the ~e~n;ng and range of equivalents are
intended to be embraced therein.
