SWART PETRUS HERMANUS (ZA)
SWART PETRUS HERMANUS (ZA)
JPH0961065A | 1997-03-07 | |||
DE2228596A1 | 1974-01-03 |
CLAIMS
1 . A DC arc furnace system comprising:
an arc furnace comprising an electrode extending into a
vessel;
- a main DC power supply connected to the electrode and to
an anode region at a base of the vessel by a main furnace
circuit comprising an anode conductor connected to the
anode region and extending from the anode region externally
of the vessel to the main DC power supply; and
- an arc deflection compensation system comprising a
compensation circuit separate from the main furnace circuit
and which compensation circuit is energized by a
compensation power supply which is separate from the main
power supply.
2. A furnace system as claimed in claim 1 wherein a main plane of
the system extends symmetrically through the main furnace
circuit and electrode.
3. A furnace system as claimed in claim 1 or claim 2 wherein the
compensation circuit is configured such that a current in the
compensation circuit causes a magnetic field in an arc region of the furnace in a direction substantially opposite to a direction of
a magnetic field in the arc region caused by a main current in
the main circuit.
4. A furnace system as claimed in claim 3 wherein the
compensation circuit is configured such that the magnetic field
caused by the current in the compensation circuit substantially
cancels the magnetic field caused by the main current in the
main circuit.
5. A furnace system as claimed in any one of claims 1 to 4
wherein the compensation circuit comprises an elongate
principal compensation limb extending substantially parallel to
the anode conductor in a region of the anode conductor towards
the anode region.
6. A furnace system as claimed in any one of claims 1 to 5
wherein the compensation circuit comprises at least first and
second coils, each comprising a plurality of windings.
7. A furnace as claimed in claim 6 wherein each of the at least
first and second coils is generally rectangular in configuration comprising substantially parallel opposed first and second longer
limbs.
8. A furnace system as claimed in claim 7 wherein the first and
second coils are arranged such that a second plane substantially
perpendicular to the main plane and below the base of the
vessel extends symmetrically through the first and second limbs
of both coils, the coils being arranged in juxtaposition relative to
one another and symmetrical relative to the main plane.
9. A furnace system as claimed in claim 7 wherein the first and
second coils are arranged below the base of the vessel, so that
respective planes parallel and symmetrical to the main plane
extend through the first and second limbs of the respective
coils.
10. A furnace system as claimed in claim 7 wherein the first and
second coils are located adjacent a sidewall of the vessel in
diametrically opposite regions of the vessel and at least partially
above the base, so that respective planes parallel and
symmetrical to the main plane extend through the first and
second limbs of the respective coils.
1 1 . A furnace system as claimed in claim 7 wherein the first and
second coils are located adjacent the vessel in diametrically
opposite regions of the vessel, so that respective planes
extending symmetrical relative to the main plane with an angle
a between the planes extend through both the first and second
limbs of the respective coils and wherein 0° < a < 180°.
12. A furnace system as claimed in any one of claims 1 to 1 1
wherein the compensation power supply comprises a single
supply.
13. A furnace system as claimed in any one of claims 6 to 1 1
wherein the compensation power supply comprises respective
power supplies for each of the at least first and second coils.
14. A furnace system as claimed in any one of claims 1 to 5
wherein the compensation circuit comprises a single coil.
15. A furnace system as claimed in claim 14 wherein the single coil
is generally rectangular in configuration having first and second
opposed limbs.
1 6. A furnace system as claimed in claim 15 wherein the main plane
extends symmetrically through the first and second limbs,
wherein the first limb is located as close as possible to the
anode conductor, wherein the coil is energized such that a
compensation current in the first limb flows in a direction
opposite to the main current in the anode conductor.
17. A furnace system as claimed in any one of claims 1 to 16
comprising a controller configured automatically to cause a
parameter in the compensation circuit to follow variations in a
corresponding or associated parameter in the main circuit.
18. An arc deflection compensation system for a DC arc furnace
comprising a main furnace circuit connecting an electrode of the
furnace to a main furnace DC power supply, the compensation
system comprising a compensation circuit separate from the
main circuit and a compensation system power supply separate
from the main power supply.
19. An arc deflection compensation system as claimed in claim 18
comprising a controller configured automatically to cause a parameter in the compensation circuit to follow variations in a
corresponding or associated parameter in the main circuit.
20. A method of adjusting arc deflection in an arc region adjacent
an electrode of a DC arc furnace and which electrode is
connected by a main furnace circuit to a main DC power supply,
the method comprising the steps of:
utilizing a separate compensation circuit located in a region
of the furnace; and
- energizing the compensation circuit with a separate
compensation power supply to cause current in the
compensation circuit to cause a magnetic field in the arc
region in a direction other than a direction of a magnetic field
in the arc region caused by a main current in the main
circuit. |
Title: COMPENSATION SYSTEM AND METHOD FOR ARC SKEWING
FOR A DC ARC FURNACE
INTRODUCTION AND BACKGROUND
This invention relates to DC arc furnaces and more particularly to a
system and method of adjusting, for example by reducing or alleviating
arc deflection or skewing in an arc region of the furnace.
A known DC arc furnace comprises a generally circular vessel in
transverse cross section comprising a closed top from which a single
electrode extends axially into a chamber defined by the vessel. The
electrode is connected as cathode by a main furnace circuit to one
pole a DC power supply. The other pole is connected to via an anode
conductor to anode terminals on a base of the vessel. Deflection of an
arc in an arc region of the furnace and which region extends between
a distal end of the electrode and a bath of molten material in the
vessel, is a known problem. The deflection is caused by a force
resulting from a transverse magnetic field in the arc region and which
magnetic field is the result of current in the main circuit. As a
consequence of the arc deflection, thermal loading on the wall of the
vessel is not symmetrical, which in turn results in uneven wear of the
wall and may result in long down times and high refractory costs.
There are various systems and methods known for reducing and/or
alleviating arc deflection, but they are not suitable for at least some
applications.
OBJECT OF THE INVENTION
Accordingly, it is an object of the present invention to provide an
alternative system and method of adjusting, for example by reducing
or alleviating arc deflection in a DC arc furnace.
SUMMARY OF THE INVENTION
According to the invention there is provided a DC arc furnace system
comprising
an arc furnace comprising an electrode extending into a vessel;
a main DC power supply connected to the electrode and to an
anode region at a base of the vessel by a main furnace circuit
comprising an anode conductor connected to the anode region
and extending from the anode region externally of the vessel to
the main DC power supply; and
an arc deflection compensation system comprising a
compensation circuit separate from the main furnace circuit and
which compensation circuit is energized by a compensation
power supply which is separate from the main power supply.
In this specification the word "separate", when used in relation to the
compensation circuit, is used to indicate that a parameter in the
compensation circuit, such as current, is independent or independently
controllable from a corresponding or associated parameter in the main
furnace circuit; and when used in relation to the compensation power
supply, that the compensation power supply is independent or
independently controllable from the main power supply. The
compensation circuit and main circuit may electrically be insulated
from one another or may share a common ground or earth.
A main plane of the system extends symmetrically through the main
furnace circuit and electrode.
The compensation circuit is configured such that a current in the
compensation circuit causes a magnetic field in an arc region of the
furnace, which arc region extends between a distal end of the
electrode and a body of material in the furnace, in a direction other
than a direction of a magnetic field in the arc region caused by a main
current in the main circuit. The other direction may be opposite to the
direction of the magnetic field caused by the main current or
transverse thereto.
The compensation circuit may be configured such that the magnetic
field caused by the current in the compensation circuit substantially
cancels the magnetic field caused by the current in the main circuit.
The compensation circuit may comprise a principal compensation limb
extending substantially parallel to the anode conductor in a region of
the anode conductor towards the anode region.
The compensation circuit may comprise at least a first and a second
coil. Each coil may comprise a plurality of windings and may have any
suitable shape or configuration such as circular, elliptical and
rectangular comprising substantially parallel opposed first and second
longer limbs.
In a first embodiment, the first and second coils may be arranged such
that a second plane substantially perpendicular to the main plane and
below the base of the vessel extends symmetrically through the first
and second limbs of both coils, the coils being arranged in
juxtaposition relative to one another and symmetrical relative to the
main plane.
In a second embodiment, the first and second coils may be arranged
below the base of the vessel, so that respective planes parallel and
symmetrical to the main plane extend through the first and second
limbs of the respective coils.
In a third embodiment, the first and second coils may be located
adjacent a sidewall of the vessel in diametrically opposite regions of
the vessel and at least partially above the base, so that respective
planes parallel and symmetrical to the main plane extend through the
first and second limbs of the respective coils.
In a fourth embodiment, the first and second coils may be located
adjacent the vessel in diametrically opposite regions of the vessel, so
that respective planes extending symmetrical relative to the main plane
with an angle a between the planes extend through both the first and
second limbs of the respective coils and wherein 0° < a < 180° .
The compensation power supply may be a single supply, alternatively
the compensation power supply may comprise respective separate
supplies for each of the at least first and second coils.
In other embodiments, the compensation circuit may comprise a single
coil of any suitable shape or configuration as aforesaid. The single coil
may be generally rectangular in configuration having first and second
opposed limbs. The main plane may extend symmetrically through the
first and second limbs, the first limb may be located as close as
possible to the anode conductor and the coil may be energized such
that a compensation current in the first limb flows in a direction
opposite to the main current in the anode conductor.
The system may comprise a controller configured automatically to
cause a parameter in the compensation circuit to follow variations in a
corresponding or associated parameter in the main circuit. For
example, the controller may be configured to operate the
compensation power supply such that the current in the compensation
circuit changes in sympathy with variations in the current in the main
circuit.
The invention also extends to a arc deflection compensation system
for a DC arc furnace comprising a main furnace circuit connecting an
electrode of the furnace to a main furnace DC power supply, the
compensation system comprising a compensation circuit separate from
the main circuit and a compensation system power supply separate
from the main power supply.
The arc deflection compensation system may comprise a controller
configured automatically to cause a parameter in the compensation
circuit to follow variations in a corresponding or associated parameter
in the main circuit. For example, the controller may be configured to
operate or control the compensation power supply such that the
current in the compensation circuit changes in sympathy with
variations in the current in the main circuit.
Yet further included within the scope of the present invention is a
method of adjusting arc deflection in an arc region of a DC arc
furnace, which region extends between an end of an electrode of the
furnace and material in the furnace and which electrode is connected
by a main furnace circuit to a main DC power supply, the method
comprising the steps of:
utilizing a separate compensation circuit located in a region of
the furnace; and
- energizing the compensation circuit with a separate
compensation power supply to cause current in the
compensation circuit to cause a magnetic field in the arc region
in a direction other than a direction of a magnetic field in the arc
region caused by a main current in the main circuit.
The other direction may be opposite to the direction of the magnetic
field caused by the main current or transverse thereto.
BRIEF DESCRIPTION OF THE ACCOMPANYING DIAGRAMS
The invention will now further be described, by way of example only,
with reference to the accompanying diagrams wherein
figure 1 is a three dimensional representation of a known or prior art
DC arc furnace;
figure 2 is a side view of the furnace in figure 1 ;
figure 3 is an end view of the furnace in figure 1 ;
figure 4 is a block diagram of a main furnace DC circuit and a
separate arc deflection compensation circuit of an arc
deflection compensation system according to the invention;
figure 5 is a diagrammatic side view of a furnace and a first
embodiment of the compensation system according to the
invention;
figure 6 is diagrammatic end view of the furnace and compensation
system in figure 5;
figure 7 is a view similar to figure 5 of the furnace and a second
embodiment of the compensation system;
figure 8 is a view similar to figure 6 of the furnace and the second
embodiment of the compensation system;
figure 9 is a view similar to figure 5 of the furnace and a third
embodiment of the compensation system;
figure 10 is a view similar to figure 6 of the furnace and the third
embodiment of the compensation system;
figure 1 1 is a view similar to figure 5 of the furnace and a fourth
embodiment of the compensation system;
figure 12 is a view similar to figure 6 of the furnace and the fourth
embodiment of the compensation system; and
figure 13 is a view similar to figure 5 of the furnace and a fifth
embodiment of the compensation system; and
figure 14 is a view similar to figure 6 of the furnace and the fifth
embodiment of the compensation system.
DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
A known Direct Current (DC) arc furnace system is generally
designated by the reference numeral 10 in figures 1 to 3.
The system 10 comprises a known arc furnace 12 comprising an
elongate tubular vessel 14 defining a chamber 16. The vessel
comprises a wall 18, which is substantially circular in transverse cross
section, a closed roof 20 and a base 22. A single electrode 24
connected to a main furnace circuit 25 extends centrally into the
vessel from the roof towards the base 22. The electrode 24 is
connected by the main circuit as cathode to a negative pole of a
known and main furnace DC power supply 28. The power supply
comprises a transformer and rectifier 30 and a coil 32 (both shown in
figure 4). A positive pole 34 of the power supply 28 is connected to
an anode region 35 of the furnace vessel at the base 22 thereof. The
cathode is connected to the negative terminal 26 of the main power
supply by a cathode arm 36 and flexible conductors 38. The anode
region is connected to the positive terminal 34 by an anode conductor
in the form of a bus-tube 40. As best shown in figure 1 , a north-south
main plane 42 extends symmetrically through the main circuit 25
components 36,38,26,32,30,34 and 40. It is known that with such
an arrangement and due to a main current L in the main circuit, there
is a resultant transverse magnetic field in an arc region 44 of the
furnace in a direction out of the paper, as shown at 46 in figure 2.
This resultant magnetic field causes an arc deflecting force Fi, causing
the arc 48 to deflect in a northern direction. The disadvantages and
problems with this deflection are set out in the introduction of this
specification. With the aforementioned symmetry about plane 42,
substantially no deflection in an east-west direction is expected.
Referring to figures 4 to 14, to alleviate or compensate for the
aforementioned deflection and according to the applicant's invention,
there is provided a compensation system 50 comprising a separate
compensation circuit 52 which is electrically insulated from the main
circuit and a separate compensation DC power supply 54 which is
electrically insulated from the main power supply and circuit.
The compensation system 50 is configured such that a compensating
transverse magnetic field is generated thereby in the arc region 44 and
in another direction, preferably opposite (that is into the paper as
shown at 56) to the magnetic field 46 caused by the main current in
the main circuit. The compensating magnetic field causes a distributed
compensating force Fc, in a direction substantially opposite to force Fi,
to be exerted on the arc 48, thereby to alleviate or compensate for the
aforementioned undesirable deflection of the arc.
The compensation circuit 52 preferably comprises at least a first and a
second generally rectangular, but could be circular or of other suitable
shape or configuration, multi-winding coils 58 and 60 and these coils
may be configured relative to the vessel 14 in various configurations
or embodiments to compensate for the aforementioned deflection, as
will hereinafter be described, merely as examples. The two coils may
be energized by a common DC power supply 54, or each may be
energized by a respective DC power supply (not shown). As best
shown in figure 4, the coils 58 and 60 are configured such that
current flow in a principal compensation limb namely adjacent legs
58.1 and 60.1 extending in a southern direction parallel to anode
conductor 40 is in a direction opposite to Im and also such that
symmetry about the plane 42 (shown in figure 1 ), is maintained.
In a first embodiment shown in figures 5 and 6, the coils 58 and 60
are positioned in a second, typically horizontal plane 61 perpendicular
to main plane 42 below the vessel. Bearing in mind the inverse square
law rule, it will be appreciated that the closer the aforementioned
adjacent legs 58.1 and 60.1 are to the arc region 44, the more
advantageous. The plane 61 extends symmetrically through both the
parallel longer limbs 58.1 and 58.2 of coil 58 and longer limbs 60.1
and 60.2 of coil 60.
in a second embodiment shown in figures 7 and 8, the coils 58,60 are
arranged below the base 22 of the vessel, so that respective planes
64, 66, which are symmetrical and parallel to main plane 42, extend
substantially symmetrical through both longer limbs of the respective
coil.
In a third embodiment shown in figures 9 and 10, the coils 58 and 60
are positioned at least partially above base 22 and adjacent the wall
14 of the vessel in diametrically opposed regions thereof, so that
respective planes 68, 70, which are substantially symmetrical and
parallel to main plan 42, extend through both longer limbs of the coils.
In a fourth embodiment shown in figures 1 1 and 12, the coils 58 and
60 are positioned adjacent wall 14 of the vessel in diametrically
opposed regions thereof, so that respective planes 71 and 73, which
are symmetrical relative to plane 42 and with an angle a between
them wherein 0° < a < 180°, extend substantially symmetrically
through both the longer limbs of the respective coils.
In a fifth embodiment shown in figures 13 and 14, a single coil 74,
which may have any suitable shape, such as rectangular, is used. The
coil comprises a first and principal compensation limb 76 and a second
opposed limb 77. The main plane 42 extends symmetrically through
both limbs and the first limb is located as close as possible to the
anode conductor of the main circuit 25 and/or the arc region 44. The
DC power supply 54 causes a compensation current Ic to flow in a
direction opposite to the main current U in the anode conductor 40.
As illustrated in figures 4 and 13 merely as example, the system 10 or
compensation system 50 may in any embodiment thereof further
comprise a controller 80 configured to control the voltage or current at
output 82 of the separate power supply 54 to change in sympathy
with any variations in the voltage at the output poles 26,34 of the
main power supply 28 or in the current Im in the main circuit 25.
In embodiments wherein the coils 58 an 60 are energized by
respective separate power supplies, the respective power supplies may
be separately controllable, to compensate for any possible east-west
deflection of the arc due to any non south-north symmetry, for
example.
Alternatively, the separate power supplies may be utilized to adjust the
arc in any desired direction, thereby to alleviate or prevent hot spot
formation in any part of the furnace wall, for example.