U.S. patent application number 10/491040 was filed with the patent office on 2004-12-02 for arc furnace and method for operating this arc furnace.
Invention is credited to Heinrich, Peter.
Application Number | 20040239017 10/491040 |
Document ID | / |
Family ID | 26010236 |
Filed Date | 2004-12-02 |
United States Patent
Application |
20040239017 |
Kind Code |
A1 |
Heinrich, Peter |
December 2, 2004 |
Arc furnace and method for operating this arc furnace
Abstract
The invention relates to an arc furnace (1), which can be tilted
or remains stationary for tapping the melt or the slag and which
comprises an eccentric and/or centric tap (9; 12). The invention
also relates to a method for operating an arc furnace (1) of this
type. The aim of the invention is to improve an arc furnace with
regard to production and to operating characteristics by making
structural changes thereto. To this end, the tap (9) is provided
inside a separately mounted projection (6) that abuts against a
terminating wall (4) of a lower vessel (2). In addition, at least
one tapping channel (5) is provided, which connects the furnace
trough (2a) and the projection (6) while passing through the
terminating wall (4).
Inventors: |
Heinrich, Peter; (Geldern,
DE) |
Correspondence
Address: |
Friedrich Kueffner
Suite 910
317 Madison Avenue
New York
NY
10017
US
|
Family ID: |
26010236 |
Appl. No.: |
10/491040 |
Filed: |
March 26, 2004 |
PCT Filed: |
September 3, 2002 |
PCT NO: |
PCT/EP02/09794 |
Current U.S.
Class: |
266/240 |
Current CPC
Class: |
Y02P 10/216 20151101;
F27B 3/19 20130101; Y02P 10/20 20151101; F27B 3/085 20130101; C21C
5/5211 20130101; F27B 3/065 20130101; F27D 3/1527 20130101; F27D
3/1536 20130101 |
Class at
Publication: |
266/240 |
International
Class: |
C21C 005/50 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 26, 2001 |
DE |
101 47 543.8 |
May 29, 2002 |
DE |
102 23 906.1 |
Claims
1. Arc furnace (1), which can be tilted or remains stationary for
tapping the melt or the slag and has an eccentric or centric tap
(9; 12), wherein the tap (9) is provided in a separately mounted
bay (6), which abuts a terminal wall (4) of a lower vessel (2), and
that at least one tapping channel (5) is provided, which passes
through the terminal wall (4) to connect the furnace shell (2a) and
the bay (6), such that the taphole (9a) of the tap (9) in the bay
(6) runs vertically in the zero position (11), i.e., the horizontal
position, of the arc furnace (1), and the tapping channel (5) runs
at an angle.
2. Arc furnace in accordance with claim 1, wherein the bay (6) can
be connected to the terminal wall (4) of the lower vessel (2a) by a
flange joint (8).
3. Arc furnace in accordance with claim 1, wherein one or more
siphon-like tapping channels (5) run through the terminal wall (4)
more or less tangent to the lining profile (10).
4. Arc furnace in accordance with claim 1, wherein the taphole (9a)
is designed with an angle adapted to the tapping angle of the
tiltable furnace (1).
5. Method of operating an arc furnace (1), which is tilted in one
swivel direction to tap the melt and in the other swivel direction
to tap the slag, such that the melt is tapped eccentrically to the
lower vessel (2), wherein first the tapping channels (5) are burned
out in the lower vessel (2) from the side of a separately mounted
bay (6), and, when the melt flows into the bay (6), the tilting
operation is initiated; in that the bay (6) is then sufficiently
filled, and the taphole (9a) is opened; and in that, when the
desired amount of melt has been tapped, the arc furnace (1) is
tilted back into the zero position (11) or beyond it.
6. Method of operating an arc furnace (1), which is tilted in one
swivel direction to tap the melt and in the other swivel direction
to tap the slag, such that the melt is tapped eccentrically to the
lower vessel (2), wherein first the tapping channels (5) are burned
out in the lower vessel (2) from the bay side, and, when the melt
flows into the bay (6) through the unclosed taphole (9a), the
tilting operation is initiated.
7. Method in accordance with claim 5, wherein, after the zero
position (11) has been reached, the tapping channel (5) and/or the
taphole (9a) is cleaned and closed with refractory material.
8. Method in accordance with claim 5, wherein, for relining
purposes, the flange joint (8) is disconnected, and the bay (6) is
removed and replaced by a relined bay (6).
9. Method in accordance with claim 5, wherein necessary fluxes and
alloys or portions of the required amounts of these additives are
added to the bay (6) during the tapping.
10. Method of operating an arc furnace (1), which is tilted in one
swivel direction to tap the melt, such that the melt is tapped
eccentrically to the lower vessel (2), wherein the tapping rate is
controlled by controlling the gas pressure in the bay (6) by
pressurization of the pressure-tight and vacuum-tight covered bay
(6) with inert gas.
11. Arc furnace (1) with a closable taphole (9a), whose lower
vessel (2) is stationary and has a bottom taphole (12), wherein the
tap (9) is provided in a separately mounted, pressure-tight and
vacuum-tight bay (6), which abuts a terminal wall (4) of the lower
vessel (2), and that at least one tapping channel (5) that passes
through the terminal wall (4) to connect the furnace shell (2a) and
the bay (6) is provided, such that the lower edge of the tapping
channel (5) on the bay side and the upper edge of the bay taphole
(9a) are at about the same level.
12. Arc furnace in accordance with claim 11, wherein the bay (6) is
provided with a pressure-tight and vacuum-tight cover (16).
13. Arc furnace in accordance with claim 11, wherein a hollow plug
(14) in a hollow plug housing (15) is mounted on the pressure-tight
and vacuum-tight cover (16), and that the hollow plug housing can
be detached or connected and opened or closed by a sluice (13).
14. Arc furnace in accordance with claim 11, wherein a gas supply
line with a gas valve (17) is connected to the pressure-tight and
vacuum-tight cover (16).
15. Method of operating an arc furnace (1) that is stationary, has
a bay (6) built onto the lower furnace (2a), and is provided with a
bay taphole (9a) and with a centric bottom taphole (12), wherein,
after the bay taphole (9a) has been opened, and the bay (6) has
been pressurized with inert gas, the tapping of the melt is
controlled in such a way that the ongoing tapping is interrupted by
reducing the negative pressure in the bay (6) as soon as the bath
level in the lower vessel (2) is below the lower edge of the
tapping channel (5) on the bay side.
16. Method in accordance with claim 15, wherein the gas pressure in
the bay (6) and in the tapping channel (5) is adjusted to a
pressure value at which the bath level is brought to the height of
the upper edge of the tapping channel (5) that runs to the lower
vessel (2).
17. Method in accordance with claim 15, wherein the tapping
operation is started by opening the bay taphole (9a).
18. Method in accordance with claim 15, wherein the tapping is
terminated by closing the open bay taphole (9a) by means of a
hollow plug (14), which can be moved in through the cover (16) and
through which sand can be poured in as far as a slide gate
(18).
19. Method in accordance with claim 15, wherein the hollow plug
(14) is replaced on the cover (16) after a sluice (13) has been
closed.
Description
[0001] The invention concerns an arc furnace, which can be tilted
or remains stationary for tapping the melt or the slag and has an
eccentric and/or centric tap, and a method of operating this arc
furnace.
[0002] The melt can be tapped on the basis of various well-known
designs of the arc furnace: Tapping can be accomplished with an
open tapping spout by tilting. Tapping can also be accomplished by
a tapping spout with a connected siphon. In arc furnaces of the
designated designs, eccentric bottom tapping in a vessel bay (EBT)
is well known (DE 82 31 869.7 U1 and DE 198 26 085 A1). Eccentric
tapping of this type is also used in an oval vessel (OBT). In
addition, centric bottom tapping (CBT) is used in circular
vessels.
[0003] Although some of these designs have proven effective, bottom
tapping can be further improved to meet operational needs.
[0004] The objective of the invention is to improve production,
in-service performance, and the operating sequence.
[0005] In accordance with the invention, this objective is achieved
by providing the tap in a separately mounted bay, which abuts a
terminal wall of a lower vessel, and by providing at least one
tapping channel that passes through the terminal wall to connect
the furnace shell and the bay. These design modifications result in
more cost-effective production, especially if the vessel is, for
example, circular or oval. The terminal wall can be continuously
formed in the region of the bay, which results in greater
dimensional stability and improved mounting of the refractory
lining. The separately mounted bay means high operational
flexibility, because this makes a bay of this type interchangeable.
An exchange of the nozzle bricks does not have to be carried out in
the hot region of the furnace. The tapping channels are readily
accessible from the bay. In individual cases, it is possible to
dispense with a bay cover. The provision of a taphole valve or a
taphole door is not absolutely necessary and can be limited to
special cases. In addition, savings of lining material are
achieved.
[0006] In an especially advantageous refinement, the bay can be
connected to the terminal wall of the lower vessel by a flange
joint. Such a flange joint may even be designed as a door that can
be swung open.
[0007] To achieve thorough emptying of the lower vessel, it is then
advantageous in accordance with other features of the invention for
one or more siphon-like tapping channels to run through the
terminal wall more or less tangent to the lining profile.
[0008] In this regard, in accordance with additional features of
the invention, the tap is arranged in such a way that the taphole
of the tap in the bay runs vertically in the zero position, i.e.,
the horizontal position, of the arc furnace.
[0009] Alternatively, the taphole may be designed with an angle
adapted to the tapping angle of the tiltable furnace.
[0010] A method of operating an arc furnace, which is tilted in one
swivel direction to tap the melt and in the other swivel direction
to tap the slag, such that the melt is tapped eccentrically to the
lower vessel, can be carried out in such a way that first the
tapping channels are burned out in the lower vessel from the bay
side, and, when the melt flows into the bay, the tilting operation
is initiated; in that the bay is then sufficiently filled, and the
taphole is opened (from the outside); and in that, when the desired
amount of melt has been tapped, the arc furnace is tilted back into
the zero position or beyond it. This results in a more advantageous
operation due to simpler operating sequences.
[0011] Another step is alternatively designed in such a way that
first the tapping channels are burned out in the lower vessel from
the bay side, and, when the melt flows into the bay through the
unclosed taphole, the tilting operation is initiated. This
eliminates the need to close the taphole.
[0012] In a refinement of the method, in an additional sequence of
steps, after the zero position has been reached, the tapping
channel and/or the taphole is cleaned and closed with refractory
material.
[0013] In an alternative embodiment, after a suitably long
operating time, for relining purposes, the flange joint is
disconnected, and the bay is removed and replaced by a relined
bay.
[0014] It is also advantageous to add necessary fluxes and alloys
or portions of the required amounts of these additives to the bay
during the tapping.
[0015] An alternative method of operating an arc furnace, which is
tilted in one swivel direction to tap the melt, such that the melt
is tapped eccentrically to the lower vessel, consists in
controlling the tapping rate by controlling the gas pressure in the
bay by pressurization of the pressure-tight and vacuum-tight
covered bay with inert gas. During this process, the taphole of the
tiltable furnace must not be closed. The siphoning effect that
develops during ongoing tapping, depending on the length of the
tapping channel between the hearth and the bay, and that manifests
itself in a negative pressure in the bay above the bath level, can
be influenced by controlling the gas pressure.
[0016] Another alternative embodiment of the invention in an arc
furnace with a closable taphole, whose lower vessel is stationary
and has a bottom taphole, is designed in such a way that the tap is
provided in a separately mounted, pressure-tight and vacuum-tight
bay, which abuts a terminal wall of the lower vessel, and that at
least one tapping channel that passes through the terminal wall to
connect the furnace shell and the bay is provided, such that the
lower edge of the tapping channel on the bay side and the upper
edge of the bay taphole are at about the same level. In this case,
the arc furnace no longer needs to be tiltable, which means that
the entire tilting mechanism is eliminated. In addition, the
operating sequences and the in-service performance change.
[0017] The necessary gas space in the bay is created by providing
the bay with a pressure-tight and vacuum-tight cover.
[0018] In addition, the bay taphole can be maintained, despite the
cover, by mounting a hollow plug in a hollow plug housing on the
pressure-tight and vacuum-tight cover. The housing can be
disconnected or connected and opened or closed by a sluice.
[0019] Other design refinements arise from the connection of a gas
supply line with a gas valve to the pressure-tight and vacuum-tight
cover.
[0020] The aforementioned alternative with a stationary arc furnace
can be regarded as the basis for a method of operating an arc
furnace that is stationary, has a bay built onto a lower furnace,
and is provided with a bay taphole and with a centric bottom
taphole. A method of this type consists in opening the bay taphole,
pressurizing the bay with inert gas, and then controlling the
tapping of the melt in such a way that the ongoing tapping is
interrupted by reducing the negative pressure in the bay as soon as
the bath level in the lower vessel is below the lower edge of the
tapping channel on the bay side. In this way, the tapping can be
interrupted with little work.
[0021] Another advantageous measure with respect to the method
consists in adjusting the gas pressure in the bay and in the
tapping channel to a pressure value at which the bath level is
brought to the height of the upper edge of the tapping channel that
runs to the lower vessel. After the bay taphole has been closed,
the bay and the tapping channel can be kept free of metal in this
way. The pressure in the bay can be adjusted in such a way that
small, steady gas consumption indicates that a small amount of gas
is bubbling into the metal bath on the furnace side of the tapping
channel. Lateral burning out or reclosing of the tapping channel
becomes superfluous with this method of operation.
[0022] In the method of operation described above, the gas pressure
inside the bay automatically drops at once when the bay taphole is
opened. Therefore, in accordance with another step of the method,
the tapping operation can be started by opening the bay taphole. At
this instant, the tapped melt starts to flow through the tapping
channels and the bay taphole without any need to tilt the furnace.
A sand filling in the bay tap is not encrusted at its surface,
because it was not exposed to a molten metal bath. It may be
assumed, therefore, that the tap opens smoothly and without
problems solely by moving away a sliding plate.
[0023] The bay taphole can be closed from above despite the
pressure-tight and vacuum-tight cover. To this end, it is proposed
that the tapping is terminated by closing the open bay taphole by
means of a hollow plug, which can be moved in through the cover and
through which sand can be poured in as far as a slide gate.
Therefore, the sand enters the bay taphole in front of the closed
slide gate through the hollow plug and fills this entire space. The
taphole prevents any pieces of scrap possibly lying on the bay
taphole from interfering with the satisfactory functioning of the
hollow plug.
[0024] The hollow plug can be changed after it has been used by
replacing it on the cover after a sluice has been closed. In
addition, a "paddle" is advantageous for preventing the sand from
running out of the bay taphole.
[0025] Embodiments of the invention are explained below with
reference to the drawings, and several methods of operating the arc
furnace are described on the basis of these embodiments.
[0026] FIG. 1 shows a cross section through a tiltable arc furnace,
in which only the lower vessel is shown.
[0027] FIG. 2 shows a top view of the arc furnace shown in FIG.
1.
[0028] FIG. 3 shows a cross section through a stationary arc
furnace, in which only the lower vessel is shown.
[0029] FIG. 4 shows a top view of the arc furnace shown in FIG.
3.
[0030] The following description refers mainly to FIGS. 1 and 2 for
the time being. The drawings show only the lower vessel 2 of an arc
furnace 1 with the furnace shell 2a lined towards the hearth 3. The
arc furnace 1 can be tilted in both swivel directions for tapping
the melt or the slag (FIG. 1).
[0031] A tap 9 for the melt is located in a separately mounted bay
6, which abuts a terminal wall 4 of the circular or oval lower
vessel 2. The terminal wall 4 is formed as an upper flange (FIG.
2). One or more siphon-like tapping channels 5 run from the hearth
3 transversely through the terminal wall 4 and completely through
the bay wall more or less tangent to the lining profile 10.
[0032] The bay 6 is detachably connected to the terminal wall 4 of
the lower vessel 2a by a flange joint 8. Corresponding flanges 7
are provided on the bay and on the lower vessel. The bay taphole 9a
runs vertically in the zero position 11 of the arc furnace 1.
Alternatively, the tap 9 can be designed with its axis at an angle
adapted to the tapping angle of the furnace 1.
[0033] The arc furnace 1 can be tipped in one swivel direction or
the other to tap the melt and the slag, such that the melt is
tapped eccentrically to the lower vessel 2. In this regard, first
the tapping channels 5 are burned out in the lower vessel 2, and,
when the melt flows into the bay 6, the tilting operation is
initiated. The bay 6 is then sufficiently filled, and the bay
taphole 9a is opened. When the desired amount of melt has been
tapped, the arc furnace 1 is tilted back into its zero position 11
or beyond it.
[0034] Another method of operation can be carried out in such a way
that first the tapping channels 5 are burned out in the lower
vessel 2 from the bay side, and, when the melt flows into the bay 6
through the unclosed tap 9, the tilting operation is initiated.
[0035] After the zero position 11 has been reached, the tapping
channel 5 and/or the bay taphole 9a is cleaned and, if necessary,
closed with refractory material.
[0036] Alternatively, for relining purposes after suitably long
production, the flange joint 8 is disconnected, and the bay 6 is
removed and replaced by a relined bay 6.
[0037] The bay 6 can also be advantageously used for the addition
of necessary fluxes and alloys or portions of the required amounts
of these additives to the bay 6 during the tapping.
[0038] The following description pertains to the stationary furnace
shown in FIGS. 3 and 4.
[0039] FIG. 3 shows a process situation in which a hollow plug 14
is inserted through a hollow plug housing 15 with the sluice 13
opened and through the pressure-tight and vacuum-tight cover 16
(with gas valve 17 closed). The bay 6 is pressurized with the gas
valve 17 open. A slide gate 18 below the bay taphole 9a is closed.
In a subsequent step of the method, the hollow plug 14 is moved
into a standby or changing position (as illustrated) with the bay
taphole 9a closed by the slide gate 18. The bay 6 is pressurized,
and inert gas bubbles out at the upper edge of the tapping channel
5 in the hearth 3. In a third step of the method, the tapping
begins. The slide gate 18 is opened, the sand filling that is
present runs out, and the bay is unpressurized relative to the
atmosphere. The molten metal is then tapped. A few seconds after
the start of the tapping, the molten metal flows through the bay
taphole 9a. In a fourth step of the method, a negative pressure
develops in the bay by the siphon principle. The hollow plug 14 is
still in the standby or changing position. In a fifth step of the
method, the hollow plug 14 moves in, the slide gate 18 closes, sand
runs in, and the bay 6 is pressurized with gas. The bay 6 runs
empty, as does the tapping channel 5. The hollow plug 14 moves out
into the standby or changing position.
[0040] The furnace can be completely emptied, if necessary, from
the bottom taphole 12.
[0041] List of Reference Numbers
[0042] 1 arc furnace
[0043] 2 lower vessel
[0044] 2a furnace shell
[0045] 3 (circular) hearth
[0046] 4 terminal wall
[0047] 5 tapping channel
[0048] 6 bay
[0049] 7 flange
[0050] 8 flange joint
[0051] 9 tap
[0052] 9a bay taphole
[0053] 10 lining profile
[0054] 11 zero position
[0055] 12 bottom taphole
[0056] 13 sluice
[0057] 14 hollow plug
[0058] 15 hollow plug housing
[0059] 16 pressure-tight and vacuum-tight cover
[0060] 17 gas valve
[0061] 18 slide gate
* * * * *