Boron carbide smelting electric arc furnace

Abstract

The utility model discloses a boron carbide smelting electric arc furnace, which relates to the technical field of electric arc furnaces, and comprises a furnace body, a conductive arm and a power supply system, a closed cavity is arranged in the furnace body and is used for smelting boron carbide; the conductive arm is horizontally arranged above the furnace body, an electrode is mounted on the conductive arm, and the electrode can move up and down in the furnace body along with the conductive arm; the power supply system is connected with the electrodes through a short net and can output direct current to the electrodes. According to the boron carbide smelting electric arc furnace, the direct-current power supply is adopted, the arc current is continuous, and the electric energy loss is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of electric arc furnaces, in particular to an electric arc furnace for smelting boron carbide. Background Art

[0002] All the electric arc furnaces for smelting boron carbide known to the utility model person are powered by three-phase 50Hz alternating current. Due to the low voltage (80V - 120V) and large current (tens of thousands of amperes) input into the furnace, a large short-circuit network voltage drop (about 10% or more of the rated voltage) and low power factor (0.8 - 0.85) are caused. With the alternating current power supply method, the electric arc will go out every time the current direction changes, and then re-strike when the instantaneous voltage value exceeds the arc-striking voltage value. Each phase electrode strikes and extinguishes the arc 100 times per second. The arc current is discontinuous, causing high-order harmonic pollution to the power grid and increasing the additional power loss. Content of the Utility Model

[0003] The purpose of the utility model is to provide an electric arc furnace for smelting boron carbide to solve the problems existing in the above-mentioned prior art. By using a DC power supply, the arc current is continuous, reducing the power loss.

[0004] To achieve the above purpose, the utility model provides the following solutions:

[0005] The utility model provides an electric arc furnace for smelting boron carbide, including:

[0006] A furnace body, which has a sealed cavity inside for smelting boron carbide;

[0007] A conductive arm, which is horizontally arranged above the furnace body, and an electrode is installed on the conductive arm, and the electrode can move up and down in the furnace body following the conductive arm;

[0008] A power supply system, which is connected to the electrode through a short-circuit network and can output direct current to the electrode.

[0009] Optionally, four of the conductive arms are evenly arranged in a ring above the furnace body, and each conductive arm is respectively installed with an electrode, and the electrodes are respectively connected to the power supply system.

[0010] Optionally, the four conductive arms are arranged in pairs in a collinear manner, and two coaxially arranged conductive arms share a set of the power supply system.

[0011] Optionally, the power supply system includes a high-voltage cabinet connected to an AC power supply, the high-voltage cabinet is respectively electrically connected to two step-down rectifiers, and the step-down rectifiers are connected to the corresponding two electrodes through a short-circuit network.

[0012] Optionally, an electrode holder is provided on the conductive arm, and the electrode holder is used for clamping the electrode.

[0013] Optionally, four guiding columns are provided on the outer side of the furnace body, and a driving device is provided on the guiding columns. The driving device is connected to the corresponding conducting arm; the driving device can control the up and down movement of the conducting arm.

[0014] Optionally, the driving device includes a lead screw drive reduction motor arranged at the top of the guiding column. The lead screw drive reduction motor is drivingly connected with a lead screw. The lead screw is vertically arranged outside the guiding column. A lead screw nut is arranged on the lead screw, and the lead screw nut is fixedly connected to the rear side of the conducting arm.

[0015] Optionally, pulleys are provided at the top of the guiding columns. A counterweight point is fixedly provided on the conducting arm. A traction wire is connected to the counterweight point. One end of the traction wire away from the counterweight point is wound around the pulley and then connected to a counterweight. The counterweight is movably arranged in the internal cavity of the guiding column.

[0016] Optionally, a control system is further included. The control system can control the output voltage of the power supply system and the lifting of the conducting arm.

[0017] Optionally, current transformers, current sharing reactors and smoothing reactors are provided in the high-voltage switch cabinet.

[0018] The utility model has achieved the following technical effects compared with the prior art:

[0019] The utility model uses a DC arc furnace to smelt boron carbide. Through the DC power supply method, there is no short-circuit network AC reactance during AC power supply, and there is no trouble with power factor. It is beneficial to the balanced power supply of the three-phase power grid, with concentrated power, stable arc, high thermal efficiency. The current supplied to the boron carbide smelting arc furnace is DC, without voltage drop due to reactance and without current zero-crossing arc extinction. All the power input into the furnace is active power, without the need for power factor compensation, eliminating the trouble of power factor problems. Under the same power supply capacity, the smelting capacity can be increased by 10% - 20%, or even higher. Without current zero-crossing arc extinction, the arc is long, the current penetration is strong, the molten pool is deep, the temperature at the lower part of the molten pool increases, and the temperature difference between the upper and lower layers of the molten pool is small, which is beneficial to promoting the reduction reaction in the furnace. The DC power is rectified from three-phase AC power by a rectifier device, so the balance of the three-phase power grid can be guaranteed. Compared with an AC furnace, the flicker effect that interferes with the power grid generated during the operation of the DC furnace is small. By taking appropriate measures, low harmonics can also be achieved, reducing the cost of harmonic control. The stability of the DC arc is better than that of the AC arc, without current zero-crossing arc extinction, with low noise and stable arc. It is convenient to strike an arc after stopping the furnace for repair and is easy to operate. The DC current has no skin effect, and the current density flowing through the electrode cross-section is uniform. Graphite electrodes with a relatively small diameter can be used, with small self-consumption of the electrodes and small power loss on the electrodes. Description of the Drawings

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0021] Figure 1 Structural schematic diagram of the present invention;

[0022] Figure 2 Partial top view schematic diagram of the present invention;

[0023] Figure 3 Structural schematic diagram of the conductive arm of the present invention;

[0024] In the figure: 1 - furnace body, 2 - conductive arm, 3 - short network, 4 - high - voltage cabinet, 5 - electrode, 6 - transformer - rectifier, 7 - electrode holder, 8 - electric cylinder, 9 - guide post, 10 - pulley, 11 - screw drive reduction motor, 12 - counterweight, 13 - counterweight point, 14 - disc spring, 15 - screw rod, 16 - screw nut. Specific implementation manners

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0026] The purpose of the present invention is to provide a boron carbide smelting electric arc furnace to solve the problems existing in the above - mentioned prior art. By using a DC power supply, the arc current is continuous, reducing power consumption.

[0027] To make the above - mentioned objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the drawings and specific implementation manners.

[0028] In the AC power supply methods known to the utility model inventors, the arc current is discontinuous, causing high - order harmonic pollution to the power grid and increasing the additional power loss. At the same time, the arc - starting current lags behind the voltage, which is also one of the main reasons for the low power factor on the low - voltage side. To improve the power factor of the electric furnace, people have proposed using reactive power compensation methods. According to the different connection points of reactive power compensation, reactive power compensation is divided into several types: high - voltage compensation, medium - voltage compensation, and low - voltage compensation. The compensation effect of high - voltage compensation can only benefit the line before the connection point, that is, the high - voltage power grid side of the power supply system, meeting the requirements of the power supply system for the power factor of this load line. However, the reactive power of the entire secondary - side low - voltage and large - current loop, including the secondary winding of the submerged - arc furnace transformer, short - net 3 copper bars, cables, electrode holders 7, and electrodes 5, is not compensated, and users cannot obtain the benefits of increased production output and reduced power consumption of the electric furnace. Low - voltage compensation can only be connected to the short - net 3 busbars connected to the soft - connection cable at the secondary outlet of the transformer. The reactive power loss from the low - voltage reactive power compensation connection point to the arc - ignition end of the electrode 5 cannot be compensated. Therefore, low - voltage reactive power compensation often fails to achieve the expected effect in many application scenarios. Medium - voltage compensation requires adding a medium - voltage compensation winding to the transformer. The volume of the capacitors for compensating reactive power in medium - voltage compensation can be reduced, but it still cannot compensate for the reactive power loss on the low - voltage side. Based on this, to solve the above problems, the utility model inventors change the original AC power supply method to a DC power supply method. The DC power supply method has no short - net 3 AC reactance during AC power supply, has no problem of power factor, is conducive to balanced power supply of the three - phase power grid, has concentrated power, stable arc, and high thermal efficiency.

[0029] Reference Figure 1 、 Figure 2 and Figure 3 As shown in

[0030] The melting method of boron carbide adopts the ingot melting method. Boron carbide has poor electrical conductivity. If the bottom electrode 5 is used, the boron carbide block generated by deposition at the bottom first will participate in conduction. First, as the boron carbide block grows, the resistance is very large, consuming electric energy and increasing energy consumption. Second, the resistance generates heat, making the temperature of the boron carbide block very high, which easily causes overheating and decomposition of boron carbide, affecting the quality of boron carbide. Third, when the boron carbide block is taken out of the furnace, the bottom of the furnace needs to move frequently, and the short circuit 3 and the water cooling system of the bottom electrode 5 will bring great trouble to the moving operation of the furnace bottom. Therefore, it is not suitable to use the bottom electrode 5 in the direct current arc furnace for smelting boron carbide. Based on this, in a preferred embodiment, four horizontally arranged current-carrying arms 2 are evenly arranged in a ring above the furnace body 1, and the four current-carrying arms 2 are arranged in a square manner. Each current-carrying arm 2 is respectively equipped with an electrode 5, and the electrodes 5 are respectively connected to the power supply system to form the layout form of the top electrode 5. The four current-carrying arms 2 are arranged in pairs on the same line, and the two current-carrying arms 2 located on the same diagonal share a set of power supply systems.

[0031] The power supply system of this embodiment includes a high-voltage cabinet 4 connected to an AC power supply. The high-voltage cabinet 4 is respectively electrically connected to two transformer rectifiers 6. The transformer rectifiers 6 are connected to the corresponding two electrodes 5 through the short circuit 3. The capacity of the transformer rectifier 6 is 500 kVA to 2000 kVA, and the total of the two sets is 1000 kVA to 4000 kVA. The high-voltage cabinet 4 supplies power to the two transformer rectifiers 6 respectively. The transformer rectifier 6 with a capacity of 500 kVA to 2000 kVA can output a direct current of 120 to 200 V and 4000 to 16000 A after rectification under the rated working state, and can be adjusted in multiple gears according to the smelting furnace conditions in real time.

[0032] The electrode 5 in this embodiment is a common graphite electrode with a diameter of 200 - 500 mm. An electrode holder 7 is provided on the conductive arm 2. The electrode holder 7 includes a clamping collar, an intermediate pull rod, and an electric cylinder 8. The clamping collar is used to hold the electrode 5. It is a known technology that the electric cylinder 8 or oil cylinder controls the clamping and loosening of the clamping collar of the electrode holder 7 through the intermediate pull rod. Generally, it includes two symmetrical semi - circles. One end of the semi - circle is hinged to the conductive arm, and the intermediate pull rod pulls the connecting ends of the two semi - circles to realize the function of the two semi - circles rotating towards each other to clamp the electrode. When the intermediate pull rod moves in the opposite direction, the two semi - circles rotate away from each other, thus loosening the electrode. Its structure and working principle are both known technologies, so no further elaboration will be made. An electric cylinder 8 is arranged at one end of the conductive arm 2 and is connected to the electrode holder 7 at the other end, which can control the clamping or loosening of the electrode holder 7. By using the electric cylinder 8 for control and mechanical clamping method, the clamping force of the electrode holder 7 can be adjusted. A disc spring 14 is sleeved on the intermediate pull rod between the electric cylinder 8 or oil cylinder and the clamping collar. The disc spring 14 is located inside the conductive arm 2 and abuts against the inner wall of the conductive arm 2. Therefore, when the intermediate pull rod moves left and right under the action of the electric cylinder 8 or oil cylinder, the disc spring 14 is compressed or stretched, which can store energy and provide a buffering function. The left - right movement of the intermediate pull rod realizes the adjustment of the clamping force of the clamping collar of the electrode holder 7, with a large clamping force and reliable operation.

[0033] Specifically, in one embodiment, four guide columns 9 are provided on the outside of the furnace body 1. A driving device is provided on the guide columns 9. The counterweight 13 is fixedly connected to the corresponding conductive arm 2. After the steel wire rope of the counterweight 13 bypasses the pulley 10 at the top of the guide column 9, it is connected to the counterweight 12. The counterweight 12 is movably installed in the internal cavity of the guide column 9, and the driving device can control the up - and - down movement of the conductive arm 2.

[0034] In a preferred mode, the driving device includes a lead - screw drive reduction motor 11, a lead screw 15, and a lead - screw nut 16. A lead - screw drive reduction motor 11 is provided at the top of the guide column 9. The lead - screw drive reduction motor 11 is the lead - screw drive motor. The lead screw 15 is vertically arranged, and its top is drivingly connected to the lead - screw drive reduction motor 11. The lead - screw nut 16 on the lead screw 15 is connected to the rear side of the conductive arm 2. By rotating the lead screw 15 with the lead - screw drive reduction motor 11, the lead screw 15 rotates in place, causing the lead - screw nut 16 to move up and down along the lead screw 15. Then, the lead - screw nut 16 drives the conductive arm 2 to rise and fall synchronously, realizing the up - and - down movement of the conductive arm 2. The driving device in this embodiment is connected to a control system, and the control system is a PLC automatic control system. Taking the furnace bottom as the zero potential, according to the actual furnace conditions during smelting, the output voltage is set. The automatic control system drives the corresponding driving device to act with the change of the arc voltage, thereby automatically adjusting the lifting of the electrode 5, and realizing the independent real - time lifting control of the four electrodes 5 respectively to ensure that the electric arc furnace works at the maximum power, with high thermal efficiency and energy conservation and consumption reduction.

[0035] In a preferred embodiment, in order to reduce the power required by the lead screw drive reduction motor 11 during the lifting process and improve safety at the same time, a counterweight 12 is provided on the side of the guide post 9 away from the counterweight point 13. The counterweight 12 is connected to a traction line. The traction line uses a steel wire rope. After the steel wire rope bypasses the pulley 10 at the top of the guide post 9, it is connected to the counterweight 12 to achieve the counterweight function of the conductive arm 2.

[0036] The high-voltage cabinet 4 of this embodiment is provided with a current transformer, a current-sharing reactor, and a smoothing reactor. The high-voltage cabinet 4 is an electrical device used in the power system, mainly for high-voltage power distribution, control, protection, and monitoring in the power distribution system. The high-voltage cabinet 4 is usually used to distribute high-voltage power from the transmission network to each user or subsystem and cut off the power supply when necessary to protect the safety of equipment and personnel. The current transformer, the current-sharing reactor, and the smoothing reactor all belong to known structures.

[0037] In the present utility model, specific examples are used to elaborate on the principle and implementation manner of the present utility model. The description of the above embodiments is only used to help understand the method and its core idea of the present utility model; at the same time, for those of ordinary skill in the art, according to the idea of the present utility model, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present utility model.

Claims

1. A boron carbide smelting electric arc furnace, characterized in that: Comprising: A furnace body having a sealed cavity therein for smelting boron carbide; A conductive arm horizontally arranged above the furnace body, and an electrode is installed on the conductive arm, and the electrode can move up and down in the furnace body following the conductive arm; A power supply system connected to the electrode through a short network and capable of outputting direct current to the electrode.

2. The boron carbide smelting electric arc furnace according to claim 1, wherein: Four of the conductive arms are evenly arranged in a ring above the furnace body, and each of the conductive arms is respectively installed with an electrode, and the electrodes are respectively connected to the power supply system.

3. The boron carbide smelting electric arc furnace according to claim 2, wherein: The four conductive arms are arranged in pairs in a collinear manner, and two coaxially arranged conductive arms share a set of the power supply system.

4. The boron carbide smelting electric arc furnace according to claim 1, wherein: The power supply system includes a high-voltage cabinet connected to an AC power supply, and the high-voltage cabinet is electrically connected to two step-down rectifiers respectively, and the step-down rectifiers are connected to the corresponding two electrodes through short networks.

5. The boron carbide smelting electric arc furnace according to claim 1, characterized in that: An electrode holder is provided on the conductive arm, and the electrode holder is used for clamping the electrode.

6. The boron carbide smelting electric arc furnace according to claim 2, wherein: Four guide columns are provided outside the furnace body, a driving device is provided on the guide columns, and the driving device is connected to the corresponding conductive arm; the driving device can control the up and down movement of the conductive arm.

7. The boron carbide smelting electric arc furnace according to claim 6, characterized in that: The driving device includes a lead screw drive reduction motor provided at the top of the guide column, the lead screw drive reduction motor is drivingly connected to a lead screw, the lead screw is vertically arranged outside the guide column, a lead screw nut is provided on the lead screw, and the lead screw nut is fixedly connected to the rear side of the conductive arm.

8. The boron carbide smelting electric arc furnace according to claim 6, characterized in that: A pulley is provided at the top of the guide column, a counterweight is fixedly provided on the conductive arm, the counterweight is connected to a traction wire, and one end of the traction wire away from the counterweight is wound around the pulley and then connected to a counterweight block, and the counterweight block is movably arranged in the internal cavity of the guide column.

9. The boron carbide smelting electric arc furnace according to claim 6, characterized in that: It further includes a control system, and the control system can control the output voltage of the power supply system and the lifting of the conductive arm.

10. The boron carbide smelting electric arc furnace according to claim 4, characterized in that: A current transformer, a current-sharing reactor and a smoothing reactor are provided in the high-voltage cabinet.

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