Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02874076 2014-11-19
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Side wall cooling for a melting furnace
Field of the invention
The present invention relates to a device for cooling a metal smelt furnace,
particularly a
reduction furnace.
Prior art
Smelting furnaces, particularly reduction furnaces, contain hot metal melts
which are
covered by a slag layer. This slag layer is frequently very aggressive and can
destroy the
wall covering of the furnace.
The furnace vessel usually comprises, in the interior, a lining in direct
contact with the melt
or slag. In order to avoid damage or destruction of the furnace vessel and
shutdown times
and costs resulting therefrom the inner wall of the furnace has to be
constantly cooled. A
metal cladding, which, for example, is cooled by an open trickle cooling, is
frequently
present on the outer side of the lining. In that case, large quantities of
water are needed,
which moreover in part run away in uncontrolled manner. A further disadvantage
is that in
the case of cracks in the cladding, water can reach the lining or melt or
slag, which can
give rise to undesired and dangerous chemical reactions. In other devices,
water boxes
are mounted on a side of the cladding remote from the melt and filled with
water. The
water can indeed thus cool, in particular, the cladding over a large area and
in a somewhat
controlled manner, but the cooling takes place at a relatively large distance
from the actual
heat source in the form of the liquid slag.
A cooling element for cooling a metallurgical furnace is known from WO
02/04192 A1,
wherein the furnace cladding of the furnace is lined at its side towards the
furnace interior
space with refractory material. The cooling element comprises a cool part,
which is flowed
through by coolant and which has a coolant feed and a coolant drain, as well
as a hot part
cooled by thermal conduction. The hot part of the cooling element is, in the
installed state,
flush with the face of the refractory material facing into the furnace
interior space. The
entire hot part is constructed as a plate and a separate cool part is
associated with this
plate at the cold side.
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European Patent Specification EP 0 741 853 B1 discloses a cooling device for a
furnace,
wherein rod-like copper rods extend into a furnace wall. Present on the rear
side of the
furnace wall is, for example, a metal plate which is cooled over a large area
by a water
box. At the outset, the complex and costly production of the disclosed system
is a
disadvantage of the disclosed arrangement. Moreover, in the case of use of a
continuous
copper plate as rear wall adjoining the furnace wall, copper rods extending
from this
plate require large amounts of copper. In addition, the load-bearing
capability of copper
is limited, so that substantial material thicknesses are necessary in order to
achieve the
requisite stability. Finally, provision of a lining between the copper rods is
also
significantly hampered.
The technical object of the present invention consists of providing a further
developed
cooling device for a smelting furnace, particularly for the cooling of the
slag region of
the furnace, but not of the metal melt bath present thereunder.
In particular, a device of that kind shall be reliable, enable a good cooling
performance
and/or be economically producible.
A device of that kind should preferably be equally usable for round furnaces.
A further object can consist in overcoming at least one of the above-mentioned
disadvantages.
Disclosure of the invention
Accordingly, the present invention relates to a cooling device for a smelting
furnace,
particularly for cooling a liquid slag in a reduction furnace. In that case,
the device
comprises a lining for (lateral) screening of a liquid metal melt bath and a
liquid slag
present on the metal melt, as well as a metal plate (or a metal cladding,
particularly steel
plate), which is arranged on a side of the lining opposite the metal melt bath
and the slag.
The metal plate comprises a plurality of slots which are substantially
vertically oriented
and arranged adjacent to one another (in horizontal direction), wherein a
respective one
of the copper plates extends through at least some, preferably each, of the
slots
substantially perpendicularly to the metal plate into the lining and the
device further
comprises cooling channels, which can be flowed
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through by coolant and which are each arranged between two mutually adjacent
slots and
the copper plates, which extend through the slots, on the side of the metal
plate remote
from the metal melt bath and the slag.
This solution represents above all a cooling which is both effective and
economic, because
on the one hand the copper plates extend as far as into the lining and on the
other hand
an economic and effective cooling of the regions between the copper plates is
made
possible. The disclosed device can in addition be used in round furnaces, for
which
production of copper elements for cooling of a lining is often made difficult.
In addition, the
material requirement of copper can be kept small from the aspect of rising raw
material
prices. In particular, the metal plate can be constructed from steel or a
steel alloy,
whereby a high level of stability as well as a saving of cost are made
possible. Moreover,
the invention is of advantage particularly in the case of aggressive slag
baths in which it is
of substantial importance for the liquid slag to solidify or 'freeze' on the
lining or the copper
plates. The thus-formed slag layer can substantially reduce wear of the lining
and/or of the
copper plates. Moreover, the concept according to the invention allows a high
degree of
stability of the furnace vessel, since a sufficient region of the metal plate
remains between
the slots through which the copper plates are introduced into the lining.
According to a preferred form of embodiment the spacing of the mutually
adjacent slots
corresponds with 1 times to 8 times, preferably 2 times to 6 times, the width
of the slots,
wherein the thickness of the copper plates preferably respectively corresponds
with at
least 70%, preferably at least 90%, of the width of the slots. These
relationships have
proved particularly advantageous for construction of a cooling device which is
equally
effective and stable.
According to a further preferred form of embodiment of the invention the
cooling channels
arranged on the metal plate extend over at least a region of a vertical length
of 80% of the
vertical length or extent of the copper plates, preferably over 100% of this
length or
preferably even over more than 100% of this length.
According to a further preferred form of embodiment of the invention the
cooling channels
extend between two mutually adjacent slots (in horizontal direction) over a
region of 40%
to 100%, preferably 50% to 90%, of the spacing (considered in horizontal
direction)
between two mutually adjacent slots.
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According to a further preferred form of embodiment of the invention the
copper plates
extend (substantially perpendicularly to the metal plate and/or at the
location of the
corresponding slot) into the lining over more than 40% of the thickness of the
lining or
extend preferably over substantially the entire thickness of the lining. The
effectiveness of
the cooling can be further improved by such an arrangement.
According to a further preferred form of embodiment of the invention the
copper plates are
in immediate or direct contact with the lining. For preference, at least 50%,
preferably at
least 75%, of the surface of the plates is in contact with the lining. This
feature also serves
for further improvement of the cooling performance.
According to a further preferred form of embodiment of the invention the
copper plates
similarly comprise channels which can be flowed through by coolant and which
are
preferably arranged in an end region of the copper plates remote from the
metal melt bath
and the slag. The heat dissipation through the copper plates can thus be
increased.
Through an arrangement of the cooling channels in an end region of the plates
remote
from the slag there is avoidance, inter alia, of water passing into the slag
or metal melt, for
example in the case of wear or mechanical damage of the plates. In general,
the
introduction of water or other coolant into the melts or slags can have
disastrous effects
and result in explosions. Moreover, linings frequently contain alkali
compounds which
equally should not come into conjunction with water in any circumstances.
According to a further preferred form of embodiment of the invention the
lining has a
thickness of 400 millimetres to 800 millimetres and preferably a thickness of
450
millimetres to 650 millimetres.
According to a further preferred form of embodiment of the invention not only
the lining, but
also the steel plate adjoining the lining are respectively of substantially
hollow-cylindrical
construction so that the hollow-cylindrical lining forms a space for lateral
enclosure of the
metal melt bath and the slag disposed thereon. The rotationally symmetrical
axis of the
hollow cylinder preferably lies in vertical direction or can also be described
as the
longitudinal axis thereof. The circumferential direction of the hollow
cylinder preferably lies
in a plane perpendicular to the axis of rotational symmetry. Alternatively,
both the lining
and the metal plate respectively form side walls of a polygonal (particularly
rectangular)
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box.
The invention is additionally directed to a furnace, particularly a reduction
furnace, which
comprises a cooling device according to any one of the preceding forms of
embodiment.
The furnace can preferably be constructed as a round furnace. This means that
the
volume, which is formed by the lining and the metal casing or the metal
cladding, for
surrounding a metal melt is constructed to be substantially (circularly) round
in a
horizontally extending cross-section. The advantages of the furnace relative
to the prior
art correspond substantially with those of the above-mentioned cooling device.
According to a preferred form of embodiment the cooling device forms a lateral
boundary
of a furnace vessel for receiving a metal melt bath and a liquid slag present
thereabove,
wherein the copper plates extend substantially in vertical direction at most
over the height
of the slag bath. In other words, the copper plates do not extend (in vertical
direction) over
a region in which the metal melt is present. This region of the lining is
preferably free of
copper plates.
In addition, the present invention is equally directed to a method for
producing a smelting
furnace or a cooling device for such, preferably a furnace or a device
according to a
respective one of the preceding forms of embodiment. In that case, the method
comprises
at least one of the following steps: providing a metal plate of substantially
hollow-cylindrical
form with slots, which are arranged adjacent to one another in the
circumferential direction
of the metal plate and which respectively extend perpendicularly to the
circumferential
direction; lining-out, in hollow-cylindrical form, the metal plate of hollow-
cylindrical form;
and introducing a respective copper plates into each of the slots. The steps
can equally
be carried out in a different sequence. Moreover, the term "metal plate" or
"metal
cladding" shall not be understood to be restricted to an integral component.
For example,
the metal plate can equally consist of a plurality of elements welded
together.
According to a preferred form of the method, this additionally comprises the
step of
providing cooling channels on the outer wall of the metal plate of hollow-
cylindrical form in
a region between the mutually adjacent slots (on the side of the metal plate
remote from
the melt or slag).
According to a further preferred form of embodiment of the method the lining
is carried out
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in such a manner that the copper plates introduced through the slots contact
the lining.
According to a further preferred form of embodiment of the method the copper
plates
extend over at least 50% of the thickness of the lining. The cooling channels
can in
general extend perpendicularly to the circumferential direction of the metal
plate of hollow-
cylindrical form over at least a region of 80% of the length of the slots in
the same
direction.
All features of the above-described forms of embodiment can be combined with
one
another or interchanged.
Brief description of the figures
The figures of the embodiments are described briefly in the following. Further
details can
be inferred from the detailed description of the embodiments. There:
Figure 1 shows a schematic side view of an outer wall of a reduction
furnace with an
embodiment of a cooling device according to the invention;
Figure 2 shows a schematic, horizontal part cross-section of a cooling
device or a
furnace according to the invention;
Figure 3 shows a schematic, vertical part cross-section of a cooling device
or a
furnace according to the invention; and
Figure 4 shows a schematic, vertical part cross-section of a further
cooling device or
furnace according to the invention.
Detailed description of the embodiments
Figure 1 shows a side view of an embodiment according to the invention of a
cooling
device. Two copper plates 7 extending substantially perpendicularly to a metal
plate or
metal cladding 5 (particularly of steel or a steel alloy) are illustrated in
the form of a detail,
which copper plates project through (longitudinal) slots 13 of the metal plate
5. Each
copper plate 7 is preferably indirectly or directly fastened to the metal
plate 5 by fastening
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means 15. The metal plate 5 in that case extends substantially in a vertical
direction V.
Such a direction can lie substantially perpendicularly to the melt or the slag
meniscus of a
metal melt M or slag S in a smelting furnace. The copper plates 7 are
preferably provided
with cooling channels 11 (not illustrated in Figure 1), which can be supplied
with coolant
via inlets 17 or outlets 19. A coolant can comprise, for example, water, but
also be formed
by other liquids. Disposed behind the illustrated view of the metal plate 5 is
a lining 3,
which is in contact with a melt and/or slag S (not illustrated). Arranged
between the
mutually adjacent copper plates 7 are, for preference, cooling channels 9 on a
side of the
metal plate 5 opposite the melt M or slag S or remote from the melt M or slag
S. These
channels 9 can comprise, for example, metal chambers, which are welded to the
metal
plate 5 or sealingly screw-connected or riveted thereto. In that case, the
channels 9 can
extend substantially parallel to the copper plates 7 and/or be arranged in
meander-shape
between the copper plates 7. The channels 9 can be supplied with coolant by
way of
inlets 21 or outlets 23. As also illustrated, the coolant channels 9
preferably extend over a
large part of the spacing A between two adjacent (but mutually spaced-apart)
copper
plates 7. The channels preferably similarly extend over at least half the
height (in vertical
direction) of the copper plates 7 or slots 13 or even, as illustrated, over
more than the
height of the copper plates 7 or the slots 13. Amongst other things, on the
one hand
copper material can be saved by the illustrated arrangement, but on the other
hand an
efficient cooling can be made possible. The copper plates 7 can in general
consist of any
copper alloy.
A part cross-sectional view of an arrangement, which is similar to Figure 1,
in horizontal
direction H is illustrated in Figure 2. The copper plates 7 extend in the
cross-sectional
view in finger-like manner in the lining 3, which is in contact with the slag
S or melt M. The
metal plate 5 as well as the lining 3 can have a curved shape. In particular,
the lining 3
and the metal plate 5 can form a lateral boundary for a metal melt M or slag S
of a round
furnace, for example a reduction furnace. In this case, the metal plate 5
and/or the lining 5
is or are of hollow-cylindrical construction. As already described with
reference to Figure
1, the copper plates 7 extend from a side (rear side), which is opposite the
slag S, of the
metal plate 5 through the metal plate into the lining 3. In that case the
lining 3 preferably
contacts the copper plates 7. The means for fastening the copper plate 7 can
comprise
angle elements or bracket elements, which protrude substantially
perpendicularly from the
metal plate 5 on both sides of a copper plate 7, wherein the copper plate 7 is
preferably
fastened to these elements by bolts or screws. Moreover, the copper plates 7
preferably
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comprise cooling channels or bores 11. These can be arranged, for improvement
in
operational reliability, in a region of a copper plates 7 which does not
project into the lining
3 or which is disposed on a side of the metal plate 5 remote from the melt M
or slag S.
In general, the lining 3 and/or the metal plate 5 can respectively be of
integral construction
or composed of a plurality of elements. Thus, the metal plate 5 can, for
example, consist
of a plurality of (plate-like) elements welded, riveted or screw-connected
together. The
assembly from a plurality of elements can be advantageous particularly in the
case of
large furnace diameters in the order or magnitude of up to 25 metres. The
lining 3 can, for
example, be mortared or cast as usual in the prior art. Moreover, a heat
conductive layer,
particularly a heat conductive layer containing carbon, can in general be
present between
the lining 3 and the metal plate 5. This can have, for example, a thickness of
several
centimetres. However, such layers are familiar to the expert.
Figure 3 shows a schematic part cross-section in vertical direction V. In
addition to the
components of the cooling device, further elements of a reduction furnace are
illustrated,
which are not, however, to be regarded as essential for the present invention.
Also shown
are the lining 3, the metal plate lying therebehind or on a side of the lining
3 remote from
the slag S or melt M, as well as a copper plate 7 protruding into the lining 3
via an opening
13 in the metal plate 5. The copper plate 7 in that case preferably extends
over at least
half the thickness of the lining 3, whereby an effective cooling or heat
dissipation is made
possible. Moreover, the copper plate 7 extends in vertical direction V
preferably merely
over a region of the slag bath S, but not over the region of the metal melt
bath M. In
particular, the slag S in contact with the lining 3 and/or the copper plate 7
can thus be
transferred into a solid state, whereby damage or wear of these elements is
reduced by
the slag S.
Figure 4 discloses, analogously to Figure 3, a schematic part cross-section of
a cooling
device or of a furnace in vertical direction V, but with the difference that
the copper plate 7
for further improvement of heat dissipation extends through or over the entire
thickness of
the lining 3.
The above-described embodiments serve primarily for a better understanding of
the
invention and should not be understood to be restrictive. The scope of
protection of the
present patent application arises from the patent claims.
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The features of the described embodiments can be combined with one another or
interchanged.
Moreover, the described features can be adapted by the expert to existing
conditions or
applicable requirements.
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Reference numeral list
3 lining
5 metal plate
7 copper plate
9 cooling channels
11 cooling channel in copper plate
13 slots in metal plate
mounting of the copper plate
17 coolant inlet of the copper plate
19 coolant outlet of the copper plate
21 coolant inlet of the cooling channel
23 coolant outlet of the cooling channel
A spacing between two mutually adjacent slots
= horizontal direction
= metal melt bath
= melt / slag
/ vertical direction / longitudinal direction of the hollow cylinder
