DC Brush-Type Electric Arc Furnace with Arc Deflection Compensation

Abstract

The present disclosure provides a DC brush-type electric arc furnace, which includes a container 12 and first and second electrodes 16, 18. A first DC power supply 20 supplies power to the electrodes. A first conductor 26 extends parallel to the first electrode such that a first current flows through the first conductor in a first direction and flows in an opposite second direction in the first electrode. A second conductor 28 extends parallel to the second electrode such that a current flows in the second electrode in the first direction and flows in the second conductor in the second direction. An arc deflection compensation system 30 includes a second DC power supply 32 and a compensation circuit 34, and the compensation circuit 34 includes a first compensation conductor 36 and a second compensation conductor 38. The second DC power supply causes a second current to flow through the first compensation conductor in the first direction and through the second compensation conductor in the second direction.

Description

[0001] Introduction and Background Art

[0002] The present disclosure relates to a furnace, and more particularly to a direct current brush-arc furnace for processing pre-reduced ore and / or preheating ore. The present disclosure also relates to a method for controlling a brush-arc in a direct current brush-arc furnace.

[0003] Known alternating current brush-arc furnaces include a container having a generally circular cross-section, the container including a closed top, and three Söderberg electrodes axially extending from the top into a chamber defined by the container. The electrodes are connected to three single-phase furnace transformers, or to a single three-phase transformer serving as the alternating current power supply for the furnace. The above-described circular container is provided with a refractory lining to provide protection against the relatively high reaction temperatures caused by the strong current generated by the furnace electrodes. A charge, typically including metallic ore, reducing agent, and flux, is continuously fed into the refractory-lined container by means of a device such as a feed chute extending through the furnace top. The charge in the furnace includes a molten alloy body or layer and a slag body or layer located above the molten alloy body or layer. The molten alloy and molten slag are periodically discharged from the molten alloy body and molten slag body, respectively, through one or more refractory-lined tapping openings in the refractory-lined container. The hot gases generated from the reaction in the furnace container are discharged through one or more discharge ducts extending through the closed top of the furnace.

[0004] One disadvantage of alternating current brush-arc furnaces is arc flash, which is caused by electromagnetic arc deflection. Arc flash causes unnecessary agitation in the slag pool and often overheats the furnace sidewalls, especially at locations opposite the electrodes.

[0005] Object of the Invention

[0006] Accordingly, an object of the present disclosure is to provide a brush-arc furnace and a method for controlling a brush-arc, which the applicant believes can at least alleviate the above problems, or can provide a useful alternative to known furnaces and methods. Summary of the Invention

[0007] According to the present disclosure, there is provided a furnace comprising:

[0008] - a container defining a chamber;

[0009] - at least one first elongated electrode and a second elongated electrode, which extend parallel to each other from respective first ends and terminate at respective second ends in the chamber;

[0010] - a direct current power supply system having a first pole and a second pole;

[0011] - A first electrical conductor extending between the first pole and the first end of the first elongated electrode, such that a first current I1 flows through the first electrical conductor in a first direction and flows from the first end of the first elongated electrode to the second end of the first elongated electrode in an opposite second direction to drive the first elongated electrode as an anode;

[0012] - A second electrical conductor extending between the second pole and the first end of the second elongated electrode, such that the first current I1 flows from the second end of the second elongated electrode to the first end of the second elongated electrode in the first direction and flows through the second electrical conductor in the second direction to drive the second elongated electrode as a cathode; and

[0013] - An arc deflection compensation system, comprising a compensation circuit connected to a DC power supply system, the compensation circuit including at least one first compensation circuit conductor portion and a second compensation circuit conductor portion, the first compensation circuit conductor portion extending parallel to the first elongated electrode, the second compensation circuit conductor portion extending parallel to the second elongated electrode, and the DC power supply system causing a second current I2 to flow through the first compensation circuit conductor portion in the first direction and through the second compensation circuit conductor portion in the second direction.

[0014] The DC power supply system may include a first DC power source and a second DC power source, wherein the first DC power source is connected to the first pole and the second pole, and the second DC power source is connected to the compensation circuit.

[0015] The first DC power source and the second DC power source may be the same power source.

[0016] The second DC power source may be different from the first DC power source and separated from the first DC power source.

[0017] The first electrical conductor may extend parallel to the first elongated electrode, and the second electrical conductor may extend parallel to the second elongated electrode.

[0018] The first electrical conductor, the first compensation circuit conductor portion, the first elongated electrode, the second elongated electrode, the second electrical conductor, and the second compensation circuit conductor portion may all extend substantially parallel to each other.

[0019] The arc deflection compensation system may include a controller for controlling the second DC power source such that the magnitude of the second current I2 can be selected or adjusted independently of the magnitude of the first current I1.

[0020] The controller may be configured to control the second DC power source so that the parameters in the compensation circuit follow the changes in the corresponding parameters in the first elongated electrode and the second elongated electrode.

[0021] The controller may be automatically configured to cause the parameters in the compensation circuit to follow the changes in the corresponding or relevant parameters in the first elongated electrode and the second elongated electrode.

[0022] For example, the controller can be configured to control the second DC power supply such that the second current I2 in the compensation circuit varies in accordance with the variation of the first current I1 in the first and second elongated electrodes.

[0023] The controller can be configured to control the second DC power supply such that the magnitude of the second current I2 can be adjusted independently of the magnitude of the first current I1.

[0024] The container can have any suitable shape, including but not limited to having a circular cross-section. In other embodiments, the container can be rectangular, and a plurality of pairs of first and second elongated electrodes are arranged on the center line of the container.

[0025] The container can include a steel shell lined with refractory material, or a refractory shell supported by a spring-loaded steel retaining structure. The container can include a top and a bottom opposite the top.

[0026] The steel shell can be kept grounded or at ground potential. The steel shell and the top can be water-cooled.

[0027] The container can include at least one feed port for loading a load into the chamber and at least one gas outlet. The at least one feed port and the at least one gas outlet can be provided at the top of the container.

[0028] The at least one feed port can include means for controlling the rate and / or volume of the load fed into the chamber for processing. The processing can include melting or smelting.

[0029] The load can include pre-reduced ore or pre-heated ore.

[0030] Pre-reduced ore is ore (including but not limited to iron ore or ferroalloy ore) aggregated into pellets or fine ore, which is reduced in a pre-reduction container and then transferred as a hot charge into the chamber for melting and / or further reduction, or cooled and then loaded into the chamber as a cold charge.

[0031] Pre-heated ore is fine ore or lump ore that is pre-heated in another container before being loaded into the furnace chamber for reduction.

[0032] The at least one gas outlet can include means for controlling the rate and / or volume of the high-temperature gas escaping from the chamber.

[0033] The at least one pair of first and second elongated electrodes can be placed to extend through the top of the container and into the chamber. The electrodes can extend towards the charge, which includes a slag body and a molten or partially molten material or metal body in the furnace chamber.

[0034] The furnace can be operated in a brush arc mode, with the second ends of the first and second elongated electrodes held a short distance above the charge in the furnace chamber. A brush arc is a short arc between the second ends of the electrodes and the charge.

[0035] The slag body can be located above the molten metal body. Due to the density difference between the slag body and the metal, the slag body and the molten metal body may separate.

[0036] The container can define a first tapping opening for discharging some slag. The container can further define a second tapping opening for discharging some molten metal.

[0037] The electrodes can be self-baking electrodes known as Söderberg type electrodes, or pre-baked graphite electrodes. The electrodes can be adjusted axially. The electrodes can each have a central axis, and these central axes can be arranged on the transverse center line of the container.

[0038] According to another aspect of the present disclosure, there is provided a method of controlling a brush arc in a DC brush arc furnace, wherein a first current flows in a first direction to a first elongated electrode of the furnace, flows through the first elongated electrode in a second direction to form a first brush arc between the first elongated electrode and the charge in the furnace, and flows through a second elongated electrode of the furnace in the first direction to form a second brush arc between the second elongated electrode and the charge, the method comprising the steps of:

[0039] - causing a second current to flow in the first direction juxtaposed with the first elongated electrode; and - causing the second current to flow in the second direction juxtaposed with the second elongated electrode,

[0040] thereby canceling the opposing magnetic fields caused by the first current in the first and second elongated electrodes and the deflections of the first and second brush arcs. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The present disclosure will now be further described, by way of example only, with reference to the accompanying drawings, in which:

[0042] Figure 1 is a schematic view of the furnace, showing an axial cross-section of the furnace container and associated circuitry;

[0043] Figure 2 is a perspective schematic view of the furnace and circuitry, with some components removed for clarity; and

[0044] Figure 3 is a three-dimensional schematic view of the furnace. DETAILED DESCRIPTION

[0045] In Figures 1 to 3 one exemplary embodiment of the furnace is generally designated by reference numeral 10.

[0046] Reference Figure 1, exemplary embodiments of the furnace include a container 12 defining a chamber 14. The container includes a top 15 (as Figure 3 shown) and a bottom 17 opposite the top. A first elongated electrode 16 and a second elongated electrode 18 extend from respective first ends 16.1, 18.1 through the top and are parallel to each other, and terminate at respective second ends 16.2, 18.2 in the chamber 14. A DC power supply system 19 includes a first DC power source 20 that supplies power to the first and second elongated electrodes 16, 18, and includes a first pole 22 and a second pole 24.

[0047] A first electrical conductor 26 preferably extends parallel to the first elongated electrode 16 between the first pole 22 and the first end 16.1 of the first elongated electrode 16, such that a first current I1 flows through the first electrical conductor 26 in a first direction A and flows from the first end 16.1 of the first elongated electrode 16 to the second end 16.2 of the first elongated electrode 16 in an opposite second direction B to drive the first elongated electrode 16 as an anode.

[0048] A second electrical conductor 28 preferably extends between the second pole 24 and the first end 18.1 of the second elongated electrode 18, preferably parallel to the second elongated electrode 18, such that the current I1 flows from the second end 18.2 of the second elongated electrode 18 to the first end 18.1 of the second elongated electrode 18 in the first direction A to drive the second elongated electrode 18 as a cathode, and then flows through the second electrical conductor 28 in the second direction B.

[0049] An arc deflection compensation system 30 includes a second DC power source 32 of the DC power supply system 19 and a compensation circuit 34. The compensation circuit 34 at least includes a first compensation circuit conductor portion 36.1 extending parallel and juxtaposed to the first elongated electrode 16 and a second compensation circuit conductor portion 38.1 extending parallel and juxtaposed to the second elongated electrode 18. The second DC power source 32 causes a second current I2 to flow through the first compensation circuit conductor portion 36.1 in the first direction A and through the second compensation circuit conductor portion 38.1 in the second direction B.

[0050] The second ends 16.2 and 18.2 of the elongated electrodes terminate a short distance above the charge 40 in the chamber 14. The charge 40 includes a molten metal body 42 or layer and a slag body 44 or layer above the molten metal body 42. In use, the electrodes 16 and 18 are driven in a brush arc mode.

[0051] It should be understood that in a furnace of the above type (but without the compensation circuit 34), according to Ampere's right-hand rule, a first current I1 flowing through the first elongated electrode 16 in the first direction A generates a first magnetic field in the first direction. According to Ampere's right-hand rule, a first current I1 flowing through the second elongated electrode 18 in the second direction B generates a second magnetic field in the opposite direction. The first and second magnetic fields interact with each other, causing the brush-shaped arc 46 between the second end 16.2 of the first elongated electrode and the charge 40 and the brush-shaped arc 48 between the second end 18.2 of the second elongated electrode and the charge 40 to deviate from each other (as shown by the dashed lines 46', 48' in Figure 1 ), resulting in arc deflection and undesirable agitation in the slag body 44 and possibly overheating and damage to the refractory 50.

[0052] The compensation system current I2 flowing through the first and second compensation circuit conductor portions 36.1, 38.1 together with the first current I1 flowing through the first and second electrical conductors 26, 28 generates a combined magnetic field that is opposite to the magnetic field generated by the current I1 flowing through the brush-shaped arcs 46', 48' (as shown by the dashed lines). This combined magnetic field is used to reduce the divergence of the brush-shaped arcs 46', 48' (as shown by the dashed lines) to the situation shown by the solid lines 46, 48, or even to the extent that the brush-shaped arcs 46, 48 can converge towards each other.

[0053] The first electrical conductor 26, the first compensation circuit conductor portion 36.1, the first elongated electrode 16, the second elongated electrode 18, the second electrical conductor 28, and the second compensation circuit conductor portion 38.1 all extend substantially parallel to each other.

[0054] In an exemplary embodiment, the compensation system 30 preferably includes a controller 51 that is configured to control the second DC power supply 32 such that the magnitude or value of a parameter such as the second current I2 is consistent with or follows the change in the first current I1 sensed by the sensing device 53.

[0055] Figure 2 and Figure 3Shows the current preferred configuration of the compensation circuit 34. The compensation circuit 34 is connected to the second DC power supply 32. The compensation circuit 34 includes a first compensation circuit conductor portion 36.1, a first semi-circular connection portion 39.1, a second compensation circuit conductor portion 38.1, a bottom connection portion 37, a third compensation circuit conductor portion 36.2, a second semi-circular connection portion 39.2, and a fourth compensation conductor portion 38.2. The second DC power supply 32 is electrically connected to the first compensation circuit conductor portion 36.1. The first compensation circuit conductor portion 36.1 extends vertically and is parallel to the first elongated electrode 16. The first compensation circuit conductor portion 36.1 is electrically connected to the second compensation circuit conductor portion 38.1 through the first semi-circular connection portion 39.1. The first semi-circular connection portion 39.1 is located in a substantially horizontal plane in the region towards the top 15 of the container 12 and extends circumferentially along the first region of the container wall. The second compensation circuit conductor portion 38.1 extends vertically and is parallel to the second elongated electrode 18. The second compensation circuit conductor portion 38.1 is electrically connected to the third compensation conductor portion 36.2 through the bottom connection portion 37. The bottom connection portion 37 is located below the container 12 and extends substantially horizontally between the second compensation circuit conductor portion 38.1 and the third compensation conductor portion 36.2. The third compensation circuit conductor portion 36.2 extends vertically and is parallel to the first elongated electrode 16. The third compensation circuit conductor portion 36.2 is electrically connected to the fourth compensation circuit conductor portion 38.2 through the second semi-circular connection portion 39.2. The second semi-circular connection portion 39.2 is also located in a substantially horizontal plane in the region towards the top 15 of the container 12 and extends circumferentially along the opposite region of the container wall. The fourth compensation circuit conductor portion 38.2 extends vertically and is parallel to the second elongated electrode 18. The fourth compensation circuit conductor portion 38.2 is electrically connected to the second DC power supply 32.

[0056] The positions of the first and third compensation circuit conductor portions 36.1, 36.2 are such that the current I2 flows through the first and third compensation circuit conductor portions 36.1, 36.2 along the same direction A. Similarly, the positions of the second and fourth compensation circuit conductors 38.1, 38.2 are such that the current I2 flows through the second and fourth compensation circuit conductors 38.1, 38.2 along the same direction B.

[0057] In an alternative embodiment, in the case where the container 12 of the furnace 10 has another shape, the semi-circular connection portions 39.1, 39.2 can be shaped according to the outer circumference of the container 12.

[0058] In the preferred embodiment, the container 12 has a circular cross-section and includes a steel shell 52 lined with refractory material 50. The steel shell is kept grounded or at ground potential.

[0059] The elongated electrodes 16, 18 are self-baking electrodes known as Söderberg-type electrodes, or pre-baked graphite electrodes. The electrodes 16, 18 are axially independently adjustable. The electrodes 16, 18 each have a central longitudinal axis, and these central longitudinal axes are arranged on the transverse center line of the circular container 12.

[0060] The container 12 includes a feed port 54 (as Figure 3 shown), through which a charge can be added to the chamber. The feed port 54 is located at the top of the container. The feed port 54 includes means for controlling the rate and / or volume of the charge fed into the chamber 14. The charge fed into the chamber 14 is processed by melting or smelting.

[0061] The container also includes an outlet (not shown) in the top 15. The outlet includes means for controlling the rate and / or volume of the gas escaping from the chamber 14.

[0062] The container 12 defines a first tapping port 56 for discharging some slag 44 and a second tapping port 58 for discharging some molten metal 42.

[0063] It should be understood that many variations can be made in the details of the furnace without departing from the scope and spirit of the present disclosure.

[0064] For example, in other exemplary embodiments of the furnace, the DC power supply system 19 may include a single DC power source that can be connected to the first and second elongated electrodes 16, 18 and the second DC power source 32.

Claims

1. A furnace (10), comprising: - A container (12) defining a chamber (14); - At least one first elongated electrode (16) and a second elongated electrode (18), the first elongated electrode (16) and the second elongated electrode (18) extending parallel to each other from respective first ends (16.1, 18.1) and terminating at respective second ends (16.2, 18.2) in the chamber; - A DC power supply system (19) having a first pole (22) and a second pole (24); - A first electrical conductor (26) extending between the first pole (22) and the first end (16.1) of the first elongated electrode (16) such that a first current I1 flows through the first electrical conductor (26) in a first direction (A) and flows from the first end (16.1) of the first elongated electrode to the second end (16.2) of the first elongated electrode in an opposite second direction (B) to drive the first elongated electrode (16) as an anode; - A second electrical conductor (28) extending between the second pole (24) and the first end (18.1) of the second elongated electrode (18) such that the first current I1 flows from the second end (18.2) of the second elongated electrode to the first end (18.1) of the second elongated electrode in the first direction (A) and flows through the second electrical conductor (28) in the second direction (B) to drive the second elongated electrode (18) as a cathode; And - An arc deflection compensation system (30), comprising a compensation circuit (34) connected to the DC power supply system (19), the compensation circuit (34) including at least one first compensation circuit conductor portion (36.1) and a second compensation circuit conductor portion (38.1), the first compensation circuit conductor portion (36.1) extending parallel to the first elongated electrode (16), the second compensation circuit conductor portion (38.1) extending parallel to the second elongated electrode (18), and the DC power supply system (19) causing a second current I2 to flow through the first compensation circuit conductor portion (36.1) in the first direction (A) and through the second compensation circuit conductor portion (38.1) in the second direction (B).

2. The furnace (10) according to claim 1, wherein, The DC power supply system (19) includes a first DC power supply (20) and a second DC power supply (32), wherein the first DC power supply is connected to the first pole (22) and the second pole (24), and the second DC power supply (32) is connected to the compensation circuit (34).

3. The furnace (10) according to claim 2, wherein, The first DC power supply (20) and the second DC power supply (32) are the same power supply.

4. The furnace (10) according to claim 2, wherein, The second DC power supply (32) is different from the first DC power supply (20) and is separated from the first DC power supply (20).

5. The furnace (10) according to claim 1, wherein, The first electrical conductor (26) extends parallel to the first elongated electrode (16), and the second electrical conductor (28) extends parallel to the second elongated electrode (18).

6. The furnace (10) according to claim 1, wherein, The first electrical conductor (26), the first compensation circuit conductor portion (36.1), the first elongated electrode (16), the second elongated electrode (18), the second electrical conductor (28), and the second compensation circuit conductor portion (38.1) all extend parallel to each other.

7. The furnace (10) according to claim 2, wherein, The arc deflection compensation system (30) includes a controller (51) for controlling the second DC power supply (32).

8. The furnace (10) according to claim 7, wherein, The controller (51) is configured to control the second DC power supply (32) such that parameters in the compensation circuit (34) follow changes in corresponding parameters in the first elongated electrode (16) and the second elongated electrode (18).

9. The furnace (10) according to claim 8, wherein, The controller (51) is automatically configured to cause parameters in the compensation circuit (34) to follow changes in corresponding or related parameters in the first elongated electrode (16) and the second elongated electrode (18).

10. The furnace (10) according to any one of claims 8 and 9, wherein, The controller (51) is configured to control the second DC power supply (32) such that a second current I2 in the compensation circuit (34) changes with a change in a first current I1 in the first elongated electrode (16) and the second elongated electrode (18).

11. The furnace (10) according to claim 7, wherein, The controller (51) is configured to control the second DC power supply (32) such that the magnitude of the second current I2 can be adjusted independently of the magnitude of the first current I1.

12. A method of controlling a brush-shaped arc in a furnace (10) according to claim 1, the method comprising the steps of: - causing the first current I1 to flow in the first electrical conductor (26) in the first direction (A); - causing the first current I1 to flow in the first elongated electrode (16) in the second direction (B) to form a first brush-shaped arc (46) between the first elongated electrode (16) and the charge (40); - causing the first current I1 to flow in the second elongated electrode (18) in the first direction (A) to form a second brush-shaped arc (48) between the second elongated electrode (18) and the charge (40); - causing the first current I1 to flow in the second electrical conductor (28) in the second direction (B); - causing the second current I2 to flow in the first compensation circuit conductor portion (36.1) in the first direction (A); and - causing the second current I2 to flow in the second compensation circuit conductor portion (38.1) in the second direction (B), thereby canceling the opposing magnetic fields caused by the first current I1 in the first and second elongated electrodes and the deflection of the first brush-shaped arc (46) and the second brush-shaped arc (48).

13. According to the method described in claim 12, wherein, Cause the magnitude of the second current to change following the change in the magnitude of the first current.

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