Note: Descriptions are shown in the official language in which they were submitted.
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Description
Membrane Cooling System For
Metallurgical Furnace
Technical Field
The present invention relates to metallurgical
apparatus and more particularly relates to a new and
improved construction for a cooling panel system of the
type for use in metallurgical furnaces, such as electric
arc furnaces or the like.
Background Art
Metallurgical processes such as electric arc furnaces
are in general use for the production of a wide variety
of iron and steel from readily available materials.
Basically, the electric arc furnace is a melting, hold-
in, or duplexing process that offers flexibility portico-
laxly for the production of special steels. In general,
the electric furnace consists of a cylindrical casing
having a convex base which provides a furnace shell and
a convex cover. The casing includes a feed and pouring
aperture with the cover being provided with apertures
to accommodate the electrodes. Conventionally, the inter-
net walls of the furnace have a more or less thick no-
factory lining serving to protect the furnace side
wall.
Heretofore, it has been found that the conventional
side wall construction utilizing metal armoring with a
refractory lining is not completely satisfactory in
standing up to tune high thermal stresses which normally
occur in these arc furnaces. Accordingly, the lining
has a relatively short fife which involves renewal of
the lining at considerable expense, as well as reduced
production. It has been recognized that water-cooled
panels have helped considerably to solve various of the
problems, namely, the life and cost of the refractory
lining in an arc furnace. It has been found that
water-cooled panels permit maintenance of higher power
input for a longer period of time. This results in
shorter heat times, increased furnace life and increased
production. Presently, there are two basic types of
water-cooled panels in use. One is the cast metal or
solid metal panel or plate type that has cooling water
pipes located internally thereof or machined therein.
The other water-cooled panel is a fabricated panel come
money referred to as a water boy. Typically these water boxes are designed as integral supporting parts of the
side walls of the furnace and are generally arranged as
segments of a circle which provides a belt-like con fig-
unction to form the side wall of the furnace. The water
boxes are fabricated with cooling water inlet and outlet
openings which enables cooling water to flow through
the box along any desired path for cooling purposes.
More recently, it has been known to provide the exposed
inner surface of the box with a multiple groove or stud
configuration to form a refractory or slag build-up
that is said to provide for heat insulation and therefore
reduction in the energy losses to the cooling water.
For reference to prior types of cooling systems
for metallurgical furnaces reference may be had to
United States Patent Nosy 2,671,65~/ 3,314,663, 3,963,223
and 4,206,312.
Disclosure of Invention
The present invention provides a new and improved
construction for a cooling lining system for a metal-
surgical furnace, such as an electrical arc furnace which comprises a bar-and-tube or undulating membrane
cooling panel construction including a single or series
of individual cooling panel sections, each of the sea--
lions comprising a plurality of cooling tubes disposed
in laterally spaced relation, the tubes being arcuate
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and/or linear in a lengthwise direction and extending
horizontally, vertically or angularly so as to define
exposed inner furnace wall surfaces, spacer bar means
are disposed centrally between adjacent cooling tubes
to provide a trough-like cavity to receive a refractory
or slag build-up, and weldments join the spacer means
bar elements with adjacent of the cooling tubes to pro-
vise a substantially continuous undulating membrane
construction which is exposed to the furnace melt (hot
face) thereby to form a surface to give a relatively
heavy build-up of refractory or slag, by adhesion, which
provides insulation barrier to reduce energy losses to
the cooling water and a protective layer to prolong -the
furnace life. In a preferred form, the panel sections
each include inwardly extending retention elements that
cocci with the bar-and-tube or membrane construction to
enhance build-up of the refractory or slag barrier layer.
In the invention, weldments on both of the panel
sides join the bar-and-tube to form homogeneous unduly-
tying membrane panel faces. The trough-like cavities
formed by the membrane surface construction with tube
radii blending into the welded bar sections, affords
basic retention surfaces which are augmented by the
"keying" effect of the retention elements which can be
quickly and easily factory or field installed.
As employed herein, the term tube includes hollow
cylinder or pipe having circular or non-circular it
polygonal) cross-sectional configurations of substanti-
ally uniform transverse dimension Preferably, the
tubes have a constant wall thickness to provide a unit
form temperature gradient for optimum heat transfer.
Also, the cooling lining system of the invention may
utilize a single panel section or a series of such panel
sections to provide the interior surface wall construe-
lion, as desired.
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By the bar-and-tube or undulating membrane combine-
lion of the invention there is provided a light weight
(i.e., compared to cast or machined metal plate panels)
yet rugged system which can be made from staple tubing
and/or from custom fabricated (formed or rolled) tubing,
as desired. The tubing being of constant or uniform
wall thickness promotes the refractory or slag adhesion
since it will have less tendency to melt-off during
the high temperature portion of the melt cycle. For
example, by the construction hot and cold spot vane-
lions are minimized, as compared to prior cast or
mechanical metal plate panels.
By this construction and arrangement, the water-
cooled panel sections ox the invention help to promote
electric furnace operation at higher temperatures and
at faster melt cycles-for higher outputs The panel
sections extend furnace life and production, assuring
many times the heats possible with use of dry refract
tories. For example, over 85 percent of the dry no-
factory above the slag line can be replaced by the lighter, water-cooled panel sections ox the invention.
This substantially lowers load and stress on the sun-
face tilt and lift mechanisms.
The bar-and-tube or undulating membrane construe-
` lion remains generally lactate in service because
ox the elimination of a substantial amount ox water
chamber welds, as compared to conventional water box
designs. The heavy duty membrane construction with-
stands gouging and damage caused during scrap charging.
In addition, the bar-and-tube arrangement with the
retention element construction provides the aforesaid
initial refractory and ultimate slag build-up, thereby
producing extra protection against metal boiling and
potential attendant panel spelling.
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In summary of the above, the invention provides an
improvement in a metallurgical furnace, such as an electric
arc furnace, of the type having a water cooling system. The
improvement comprises a membrane cooling panel construction which
is made from a plurality of individual cooling panel sections.
These panel- sections are disposed in an end-to-end relation-
ship and are oriented circumferential so that they define an
inner exposed hot wall surface. Each panel section comprises a
plurality of generally cylindrical cooling tubes which are
disposed in a substantially parallel, juxtaposed relation and
are spaced laterally apart by a sufficient distance in order to
define a lateral spacemen area there between. The cooling tubes
are oriented circumferential to define the hot wall surface.
Spacer bar means are disposed in a generally centered relation
in the spacemen area between -the cooling tubes, and have a
widths dimension sufficient to provide a trough-like recess
there between. The spacer bar means are provided in order to
hold the individual cooling tubes from contacting each other.
The associated spacer bar means are joined to the adjacent
surfaces of the cooling tubes by weldments in order to provide
a substantially continuous, undulating membrane surface which
is exposed to the furnace melt The improvement also includes
a source of cooling fluid for delivering a cooling fluid to the
cooling tubes.
Other further advantages and features of the invention
will become
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apparent when taken in reference to the following
description and drawings in connection with the annexed
claims.
Brief Description of the Drawings
Figure 1 is a vertical section view through a
schematic construction of an electric arc furnace
which incorporates the water cooling lining system of
the invention;
Figure 2 is a front (cold side) elevation view
of an individual panel section on a reduced scale
made in accordance with the invention;
Figure 3 is a top elevation view schematically
illustrating a series of the individual panel sections
circumferential mounted to define an interior furnace
side wall in accordance with the invention;
Figure 4 is a fragmentary section view taken
along line 4-4 of Figure 2;
Figure 5 is a fragmentary section view taken
along line 5 5 of Figure 3;
Figure 6 is a fragmentary section view taken
along line 6-6 of Figure 3.
Figure 7 is a top plan view of a modification of
a panel section made in accordance with the invention;
Figure 8 is a front elevation view of the panel
section of Figure 7;
Figure 9 is a vertical section view of the panel
section of Figure 7;
Figure 10 is a fragmentary vertical section view,
on an elongated scale, illustrating utilization of
the retainer elements for maintaining a refractory
build-up;
Figure 11 is a fragmentary vertical section view,
on an enlarged scale, illustrating utilization of a
modified form of the retainer elements made in accord-
ante with the invention; and
Figure 12 is a horizontal section view, on an
enlarged scale, taken along the line 12-12 ox Figure 8.
Best Mode For Carrying Out The Invention
Referring again now to the drawings and in portico-
far to Figure 1 thereof, there is illustrated a convent
tonal type electric arc furnace, designated generally
at 2, and of the type of which the present invention
may be employed. It is to be understood, however,
the invention may be employed with other types of
metallurgical furnaces or apparatus, such as in open
hearth furnaces as in the lintel and door areas, for
example. As shown, the furnace 2 includes a convex
base 6 having a refractory bottom lining inside a
metal shell S. Electrodes 8 and 10 extend through
the top of the furnace together with a gas discharge
pipe 14, as known in the art. Accordingly, the present
invention provides a water-cooled membrane system,
designated generally at 16, which provides a surface
that gives a protective, insulation barrier layer, in
the form of a refractory and slag build-up, to reduce
energy losses to the cooling water resulting from the
high thermal temperatures of the melt.
Now in accordance with one form of the invention,
the cooling system may include a series, such as six,
individual panel sections (Figure 3) 17 mounted above
the slag line within the furnace shell S to provide a
cylindrical configuration so as to accommodate the
curvature of the furnace shell. In the embodiment
illustrated, each panel section 17 includes a plural-
fly of elongated, hollow tubes 18 which are spaced laterally from one another and which extend horizon-
tally or at right angles to the vertical central axis
of the furnace. accordingly, the tubes 18 are formed
with the required curvature to provide an arcuate
configuration to give the ultimate cylindrical configure-
lion desired. It will be understood, however, that the tubes 18 can be linear, as in the case of larger
diameter furnaces, rather than being curved, shown.
Also, it will be recognized that the tubes can extend
vertically or parallel to the vertical central axis
of the furnace, as desired.
As best seen in Figure 5, the individual tubes
18 are fixedly attached to one another by individual
spacer means in the form ox bar elements 26 which
extend centrally there between. The spacer bar elements
26, therefore, lie in a common plane which contains
the longitudinal central axis of the respective tubes
18 so as to provide a trough-like cavity or recess
between adjacent pipes. In the invention, the spacer
bar elements 26 are fixedly secured to the adjacent
tubes 18 by weldments, as at 30, which partially fill
the trough like cavity or recess between adjacent
tubes. By this construction and arrangement, there
is provided a continuous, undulating membrane surface
which is exposed to the furnace melt (hot face) to
provide for a build-up of refractory and slag. This
build-up creates, in effect, a refractory insulation
barrier layer which provides a surface that gives a
protective and heat barrier against energy losses
caused by the cooling water circulated through the
tubes 18. The opposite sides of the spacer bar eye-
mints 26 may be provided with additional weldments,
as at 28, to enhance the strength characteristics of
the membrane panel. In the invention, the retention
means may be separate bars, rods or the like or may
include tubes with integral bar-like flanges that
could be welded together.
As best seen in Figures 3, and 5, each panel
section is provided with an upper cooling tube 22
(hot face) disposed in vertical alignment with the
inner tubes 18 and a laterally outwardly by disposed
tube (cold face) 24 which are integrally joined to-
getter by weldments, as at 30, to provide a dual tube
construction at the top of the panel section Also,
the panel section may be provided with a similar lower
22' and outer 24' dual tube construction at the lower
end of the panel section. To further enhance the
strength characteristics of the individual panels,
vertically extending support plates, as at 60, may be
fixedly attached, as by weldments, to the correspond-
in rear surfaces of associated of the cooling tubes
18, 24 and 24. A -top plate 62 may be welded to the
upper inner tube 24 and to the header tubes 40 and 42
to provide a support flange for mounting on the furnace
shell S, as seen in Figure 1. By such arrangement,
structural support is given to the cooling tubes in
the event of impact forces from the hot face side.
Now in accordance with the invention, the panel
sections 17 are provided with a pair of vertically
extending header members 40 and 42 for circulating
MU the flow of cooling water from a supply source (not
shown) through the tubing system for discharge. For
this purpose, each panel section may be provided with
a cooling water inlet 32 (Figure 2) and an outlet 34
which includes an outlet pipe 36 disposed within the
header member 40. The header member 40 communicates
the inlet 32 via a chamber 46 (Figure 1) with the
cooling tubes 18. The header 40 connects the outlet
34 of the outlet pipe 36 via a chamber 52 with the
cooling tubes for discharge of the cooling fluid.
Suitable baffle plate members (Figure 6) 48 and 50
may be disposed within the chamber of the header member
receive the outlet pipe 36 there through.
accordingly, the chambers may be separated by
baffle plates 44, 48 and 50 kick separate the chambers
from one another and hence, the inlet and outlet from
one another. As will best be seen in Figure I, the
cooling tubes 22 and 24, for example, include internal
passageways 37 and 39 which extend through correspond-
in apertures provided in the header member 40 for
circulating cooling water flow through the tubes in
any predetermined path between the headers 40 and 42.
In the invention, it will be recognized that the
interior configuration of the cooling pipes may be
constructed and arranged so as to provide any desired
path for the coolant. For example, the coolant may
follow any flow (i.e., single linear line, serpentine
or the like) path with the pipe lengths being disposed
horizontally, vertically or at an angle.
While a specific embodiment of the invention has
been shown and described in detail to illustrate the
application of the principals of the invention, it
will be understood that the invention may be embodied
otherwise without departing from such principals, as
will be seen in reference to following Figures 7-12
of the drawings, for example.
Referring now to Figures 7, 8 and 9, there is
illustrated a modification of the panel section, design
noted generally at 70, made in accordance with the
present invention. In the embodiment shown, the panel
section 70 includes a plurality of vertically spaced
tubes 72 which are laterally spaced by spacer bar
elements 74. The tubes 72 are welded, as at 76, to a
series of vertically extending support members 80
which abut against the interior surface of the fur-
nice wall to protect against hot face impact faces or
the like, as aforesaid. Here again, the spacer bar
elements 74 extend in the general medial plane which
contains the longitudinal axis of the tubes 72 and
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are welded to the tubes so as to provide a trough-
like cavity or recess there between.
In the embodiment illustrated, the tubes 72 are
provided with horizontally extending retainer elements
78 in the form of solid metal bar elements which are
welded to the outer confronting surface of the respect
live tubes. These retainer elements 78 provide an
irregular exposed surface area -to give a "key" effect
so as to enhance build-up of a refractory and slag
layer on the continuous, undulating membrane surface
provided by the associated tubes 72 and spacer bar
elements 74. In the invention, it will be appreciated
that the retainer elements can be of a hollow or solid
construction and of any cross-sectional shape, as
desired.
As best illustrated in Figure 7, the tubes 72,
bar elements 74 and retainer elements, 78 are bent
(i.e., fabricated or rolled) generally at the mid-
point thereof so as to provide a non-linear configure-
lion. By this arrangement, the panel section provides membrane surface which is not just curved nor linear
but which incorporates a dual curved and linear con-
s-truction so as to define the interior side wall surf
face of the furnace. It will be understood, there-
fore, that the respective panel sections can be pro-
voided with curved, linear or a composite configure-
lions thereof. Also, it will be seen that in the
invention that the panel tubes could be disposed at
various angles in respect to one another to accommo-
date metallurgical furnace applications (i.e., in-
dined or shaped side walls) requiring conical or
trapezoidal shaped panel sections, for example.
As best illustrated in Figure 10, the retainer
elements 78 cocci with the -tubes 72 and spacer bar
elements I to enable the user to apply a refractory
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layer, as at R, to the undulating membrane surface.
Accordingly, the present invention provides a con-
struction which provides either a natural build-up of
refractory and slag or which enables the user to build-
up such layer, as desired.
In the embodiment illustrated, the panel section
70 includes header members 90, 92 which are of a hot-
low tube (formed or rolled) construction. According-
lye the tubes 72 communicate at their opposed ends
with the header members 90, 92 (figure 12) such that
cooling fluid can be introduced through the inlet, at
94, so as to travel a predetermined path through the
tubes and out through the outlet tube US, as described
in connection with the cooling fluid flow of Figure
6. Accordingly, in this embodiment cooling fluid may
enter the inlet 94 and traverse the tubes 72 into the
header member 92 and then back through tubes 72 into
header member 90 and so on until the cooling fluid
enters the top of the outlet tube 95 in the header
member 90 so as to be discharged through the outlet
96. Here again, it will be understood that the cooling
fluid flow may take any path through the panel section
dependent upon the construction and design of the
tube configuration as desired.
As best illustrated in Figure 12, the respective
header members 90, 92 may each be provided with curved
retainer elements 88 in the form of solid bars which
are vertically spaced so as to coincide in alignment
and number with the retainer elements 78 on the tubes
72. By this arrangement, the header members are also
protected and cocci with the tubes 72 so as to provide
a substantially continuous refractory and slag build-
up on the membrane surface to optimize the protective
and insulation characteristics of the panel sections
against energy loss to the cooling system.
Lo
In Figure 11 there is illustrated a further mod-
ligation of the present invention wherein the tubes
72 are provided with retainer elements 86 which are
of a stud-like construction welded at an angle to the
respective tubes 72. Accordingly, the retainer eye-
mints 86 preferably extend divergently outwardly from
the associated tubes 72 and may be of a polygonal
configuration in transverse cross-section. Here again,
this retainer arrangement facilitates the holdup of
a refractory Andre slag layer, as at R, either by
natural build-up or by an external build-up, as alone-
said.
As best illustrated in Figures 8 and I a -top
plate member 82 may be mounted, as with plate 62,
which provides a supporting flange for mounting on
the outer furnace shell. In the invention, it is
contemplated that the individual panel sections and/or
a series of such sections may be detachably mounted
interiorly of the furnace shell by various systems
such as bolts, wedge block or the like.
Accordingly, while four forms of the invention
have been illustrated for purposes of example, it
will be understood that other forms and modifications
are contemplated and possible within the scope ox the
present invention as determined by the scope of the
following claims.
