Direct-current electric arc furnace auxiliary electrode and control method thereof

Abstract

The invention discloses an auxiliary electrode of a direct-current electric arc furnace and a control method thereof, and belongs to the technical field of electric arc furnaces. By arranging an auxiliary anode, the cathode current of the electric arc furnace is increased under the condition that the anode current of the electric arc furnace is not changed, so that the temperature of a cathode molten pool of the electric arc furnace is increased; the auxiliary anode does not need to be additionally provided with a direct-current power supply, silicon controlled rectifier power supplies of the anode and the cathode of the electric arc furnace are directly utilized, equipment investment is greatly reduced, the power supply structure is simplified, and besides the silicon controlled rectifier four-electrode without the bottom electrode, the method is also suitable for the direct-current electric arc furnace with six or more electrodes. The two IGBTs can be combined into one IGBT.

Description

Technical Field

[0001] The invention belongs to the technical field of electric arc furnaces, in particular to an auxiliary electrode of a direct current electric arc furnace and a control method thereof. Background Art

[0002] At present, the temperature of the two anode molten pools of the thyristor rectifier four-electrode DC arc furnace without bottom electrode is obviously higher than the temperature of the two cathode molten pools, which leads to inconsistent temperature inside the electric furnace, especially the temperature of the center of the furnace and the temperature of the cathode molten pool of the arc furnace are low, which affects the requirements of electric furnace smelting production and has a great impact on product quality, output and unit energy consumption. This is a common problem of the thyristor rectifier four-electrode DC arc furnace without bottom electrode, and it is urgent to solve this problem. Summary of the invention

[0003] The technical solution of the present invention is as follows: a DC electric arc furnace auxiliary electrode, comprising: a first thyristor rectifier, a first electric arc furnace anode, a first electric arc furnace cathode, a second thyristor rectifier, a second electric arc furnace anode, a second electric arc furnace cathode, a first IGBT, a second IGBT and an auxiliary anode, wherein the first thyristor rectifier, the first electric arc furnace anode and the first electric arc furnace cathode form a power supply circuit; the second thyristor rectifier, the second electric arc furnace anode and the second electric arc furnace cathode form another power supply circuit; the first IGBT, the second IGBT, the auxiliary anode, the first electric arc furnace cathode and the second arc furnace cathode form an auxiliary power supply circuit.

[0004] Furthermore, the collector of the first IGBT is connected to the positive electrode of the first thyristor rectifier, the collector of the second IGBT is connected to the positive electrode of the second thyristor rectifier, and the emitters of the first IGBT and the second IGBT are connected and then connected to the auxiliary anode.

[0005] Furthermore, the thyristor rectifier is a 2000A / 50V thyristor rectifier power supply.

[0006] Furthermore, the current of the first arc furnace anode and the first arc furnace cathode is 1210A, and the current of the second arc furnace anode and the second arc furnace cathode is 1200A.

[0007] Further, the voltage between the first arc furnace anode and the first arc furnace cathode is 43.5V, and the voltage between the second arc furnace anode and the second arc furnace cathode is 42.6V.

[0008] A method for controlling an auxiliary electrode of a DC electric arc furnace. When a control circuit turns on a first IGBT, the potential of the auxiliary anode is the same as the positive electrode of a first thyristor rectifier, and current flows between the auxiliary anode and the cathode of the first electric arc furnace. The control circuit is used to adjust the duty ratio of the first IGBT being turned on and off, and the magnitude of the auxiliary anode current is controlled. When a control circuit turns on a second IGBT, the potential of the auxiliary anode is the same as the positive electrode of the second thyristor rectifier, and current flows between the auxiliary anode and the cathode of the second electric arc furnace. The control circuit is used to adjust the duty ratio of the second IGBT being turned on and off, and the magnitude of the auxiliary anode current is controlled.

[0009] The beneficial effects of the present invention are:

[0010] The auxiliary anode is set to increase the cathode current of the arc furnace while ensuring that the anode current of the arc furnace remains unchanged, thereby increasing the temperature of the cathode molten pool of the arc furnace; the auxiliary anode does not need to add an additional DC power supply, and directly uses the thyristor rectifier power supply of the anode and cathode of the arc furnace, which greatly reduces equipment investment and simplifies the power supply structure. In addition to the thyristor rectifier four-electrode without bottom electrode proposed by the present invention, it is also applicable to DC arc furnaces with six electrodes or more electrodes, and IGBT1 and IGBT2 can also be combined into one IGBT. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 Schematic diagram of the circuit of the present invention.

[0012] In the figure:

[0013] 1 first thyristor rectifier, 2 first arc furnace anode, 3 first arc furnace cathode, 4 second thyristor rectifier, 5 second arc furnace anode, 6 second arc furnace cathode, 7 first IGBT, 8 second IGBT, 9 auxiliary anode, 10 arc furnace wall. DETAILED DESCRIPTION

[0014] It should be noted that in the description of the present invention, the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", "clockwise", "counterclockwise", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction.

[0015] In the present invention, unless otherwise clearly specified and limited, the terms "set", "install", "connect", "connect" and the like should be understood in a broad sense. For example, "fixed" can be a fixed connection, a detachable connection, or an integral connection; the connection can be a mechanical connection or an electrical connection; the connection can be a direct connection or an indirect connection through an intermediate medium, and can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0016] A DC electric arc furnace auxiliary electrode comprises a first thyristor rectifier 1, a first electric arc furnace anode 2, a first electric arc furnace cathode 3, a second thyristor rectifier 4, a second electric arc furnace anode 5, a second electric arc furnace cathode 6, a first IGBT 7, a second IGBT 8 and an auxiliary anode 9.

[0017] The first thyristor rectifier 1, the first arc furnace anode 2 and the first arc furnace cathode 3 constitute a power supply circuit of the previous thyristor rectifier four-electrode DC arc furnace, and the second thyristor rectifier 4, the second arc furnace anode 5 and the second arc furnace cathode 6 constitute another power supply circuit of the previous thyristor rectifier four-electrode DC arc furnace. The first IGBT 7, the second IGBT 8, the auxiliary anode 9, the first arc furnace cathode 3 and the second arc furnace cathode 6 constitute the auxiliary power supply circuit of the present invention.

[0018] Previously, when the current of the arc furnace anode and the arc furnace cathode was the same, the temperature of the arc furnace anode molten pool was significantly higher than the temperature of the arc furnace cathode molten pool, thus creating a low-temperature zone near the arc furnace cathode, affecting metal smelting.

[0019] The method is to add an electric arc furnace auxiliary anode 9, which is connected to the positive electrode of the first thyristor rectifier 1 through the collector of the first IGBT 7, the collector of the second IGBT 8 is connected to the positive electrode of the second thyristor rectifier 4, the emitters of the first IGBT 7 and the second IGBT 8 are connected, and then connected to the auxiliary anode 9; when the control circuit turns on the first IGBT 7, the potential of the auxiliary anode 9 is the same as the positive electrode of the first thyristor rectifier 1 (ignoring the conduction voltage drop of the first IGBT 7), and current flows between the auxiliary anode 9 and the cathode 3 of the first electric arc furnace. The magnitude of the current of the auxiliary anode 9 can be controlled by adjusting the duty cycle of the conduction and shutdown of the first IGBT 7 through the control circuit; when the control circuit turns on the second IGBT 8, the potential of the auxiliary anode 9 is the same as the positive electrode of the second thyristor rectifier 4 (ignoring the conduction voltage drop of the second IGBT 8), and the auxiliary anode 9 is connected to the positive electrode of the second thyristor rectifier 4. Current flows between the anode 9 and the cathode 6 of the second arc furnace. The current of the auxiliary anode 9 can be controlled by adjusting the duty cycle of the on and off of the second IGBT8 through the control circuit; the current of the auxiliary anode 9 does not affect the current of the anode and cathode of the arc furnace, so that the current of the cathode of the arc furnace can be appropriately increased while the anode current of the arc furnace remains unchanged, thereby ensuring that the temperature of the molten pool of all electrodes in the arc furnace is basically the same. As long as the position of the arc furnace electrodes is reasonably arranged, the temperature of the smelting area inside the entire DC furnace can be guaranteed to fully meet the production requirements, thereby completely solving the problems of low furnace center temperature and low arc furnace cathode molten pool temperature that were common in the previous thyristor rectifier four-electrode DC arc furnace without a bottom electrode, which has a significant effect on improving product quality, output and reducing unit energy consumption, and at the same time provides technical feasibility for the future development of ultra-high power DC arc furnaces.

[0020] In the example verification, two 2000A / 50V thyristor rectifier power supplies, 5 graphite electrodes and silicon manganese raw materials were used for the experiment. The constant current control method was adopted. The current of arc furnace anode 1 and arc furnace cathode 1 was 1210A, the current of arc furnace anode 2 and arc furnace cathode 2 was 1200A, the voltage between arc furnace anode 1 and arc furnace cathode 1 was 43.5V, and the voltage between arc furnace anode 2 and arc furnace cathode 2 was 42.6V. After 60 minutes, the temperatures near the four electrodes were measured by infrared thermometer: arc furnace anode 1 temperature: 1060℃, arc furnace anode 2 temperature: 1052℃, arc furnace cathode 1 temperature: 908℃, arc furnace cathode 2 temperature: 905℃. When the auxiliary anode was inserted, the current and voltage of the cathode and cathode of the arc furnace basically did not change. IGBT1 and IGBT2 also use constant current control when working. When IGBT1 and IGBT2 work at the same time, the current is 60A (the auxiliary anode current is 120A). At this time, the voltage between the arc furnace anode 1 and the arc furnace cathode 1 is 44.5V, and the voltage between the arc furnace anode 2 and the arc furnace cathode 2 is 43.6V. After 30 minutes, the temperatures near the five electrodes are measured as follows: arc furnace anode 1 temperature: 1080°C, arc furnace anode 2 temperature: 1076℃, arc furnace cathode 1 temperature: 1035℃, arc furnace cathode 2 temperature: 1030℃, auxiliary anode temperature: 10 63℃; when IGBT1 and IGBT2 are working at the same time, the current is 150A (the auxiliary anode current is 300A), the voltage between the arc furnace anode 1 and the arc furnace cathode 1 is 46.1V, and the voltage between the arc furnace anode 2 and the arc furnace cathode 2 is 45.6V. After 30 minutes, the temperatures near the five electrodes are measured as follows: arc furnace anode 1 temperature: 1087℃, arc furnace anode 2 temperature: 1081℃, arc furnace cathode 1 temperature: 1083℃, arc furnace cathode 2 temperature: 1080℃, auxiliary anode temperature: 1089℃; the temperature in the whole furnace is relatively uniform, and the effect is very good.

[0021] The above is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any modification, equivalent replacement and improvement made by any person skilled in the art within the technical scope disclosed by the present invention and within the spirit and principle of the present invention shall be covered within the protection scope of the present invention. At the same time, the contents not described in detail in this specification belong to the prior art known to those skilled in the art.

[0022] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

Claims

1. A DC arc furnace auxiliary electrode, characterized in that: include: The first thyristor rectifier, the first arc furnace anode, the first arc furnace cathode, the second thyristor rectifier, the second arc furnace anode, the second arc furnace cathode, the first IGBT, the second IGBT and the auxiliary anode, wherein the first thyristor rectifier, the first arc furnace anode and the first arc furnace cathode form a power supply circuit; the second thyristor rectifier, the second arc furnace anode and the second arc furnace cathode form another power supply circuit; the first IGBT, the second IGBT, the auxiliary anode, the first arc furnace cathode and the second arc furnace cathode form an auxiliary power supply circuit.

2. The auxiliary electrode for a DC arc furnace according to claim 1, characterized in that: The collector of the first IGBT is connected to the positive electrode of the first thyristor rectifier, the collector of the second IGBT is connected to the positive electrode of the second thyristor rectifier, and the emitters of the first IGBT and the second IGBT are connected and then connected to the auxiliary anode.

3. The auxiliary electrode for a DC arc furnace according to claim 1, characterized in that: The thyristor rectifier is a 2000A / 50V thyristor rectifier power supply.

4. The DC arc furnace auxiliary electrode according to claim 1, characterized in that: The current of the first arc furnace anode and the first arc furnace cathode is 1210A, and the current of the second arc furnace anode and the second arc furnace cathode is 1200A.

5. The DC arc furnace auxiliary electrode according to claim 1, characterized in that: The voltage between the first arc furnace anode and the first arc furnace cathode is 43.5V, and the voltage between the second arc furnace anode and the second arc furnace cathode is 42.6V.

6. A DC arc furnace auxiliary electrode control method, characterized in that: When the control circuit turns on the first IGBT, the potential of the auxiliary anode is the same as the positive electrode of the first thyristor rectifier, and current flows between the auxiliary anode and the cathode of the first arc furnace. The control circuit is used to adjust the duty cycle of the first IGBT being turned on and off, thereby controlling the magnitude of the auxiliary anode current. When the control circuit turns on the second IGBT, the potential of the auxiliary anode is the same as the positive electrode of the second thyristor rectifier, and current flows between the auxiliary anode and the cathode of the second arc furnace. The control circuit is used to adjust the duty cycle of the second IGBT being turned on and off to control the magnitude of the auxiliary anode current.

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