Large energy-saving direct current submerged arc furnace

Abstract

The invention relates to the technical field of submerged arc furnaces, and discloses a large energy-saving direct-current submerged arc furnace which comprises a bottom plate and a fixing frame arranged on the bottom plate. According to the large energy-saving direct-current submerged arc furnace, the particle size of ore is controlled through extrusion and crushing, materials are automatically stricken by a strickling plate, a conical rod rotates and guides, the particle size is screened according to intervals, and ferromagnetic impurities are removed through a magnetic attraction belt; the electrode and furnace lining loss is reduced; inert gas is introduced into an airflow plate of a heating furnace to strengthen stirring of a molten pool and promote full contact of effective components and a fluxing agent, a full-direct-current framework is adopted to eliminate alternating loss, a double-inverse-star-shaped non-in-phase inverse parallel topology is matched, and mutual counteraction of current and a magnetic field is utilized, so that the material with the particle size exceeding the standard is obtained. Copper pipe hysteresis and eddy current loss are reduced, the operating temperature is controlled, the topological multi-pulse rectification optimizes the current waveform, the reactive power is reduced, and a high-capacity reactive power compensation device is omitted; and meanwhile, the length of the short net is shortened, the conductor section is optimized, an additional heat dissipation pipeline is not needed, and energy consumption and investment are reduced.

Description

Technical Field

[0001] This invention relates to the field of electric arc furnace technology, specifically a large-scale energy-saving DC electric arc furnace. Background Technology

[0002] A submerged arc furnace is an electrically heated device used in the metallurgical industry to extract metals from ores. It is primarily used to produce ferroalloys, ferrosilicon, and ferromanganese, and sometimes for processing waste slag or recovering rare metals. Submerged arc furnaces operate based on the Joule heating effect generated when an electric current passes through a resistor. When the current flows, an electric arc forms between the electrodes, generating high temperatures sufficient to melt the ore and reducing agent, and promoting chemical reactions that reduce the metal from its oxides. Currently, most submerged arc furnaces in China are AC-powered, which have revealed numerous prominent problems in actual operation, severely hindering the industry's green and low-carbon transformation and economic efficiency improvement.

[0003] Existing AC submerged arc furnaces suffer from eddy current losses and hysteresis losses due to the alternating magnetic field, as well as high short-circuit impedance, resulting in high power consumption per unit product. Furthermore, the alternating magnetic field generates a large amount of reactive power, leading to a generally low power factor. This necessitates the installation of large-capacity reactive power compensation devices, increasing equipment investment and maintenance costs. At the same time, traditional submerged arc furnaces have strict requirements on the grade and particle size of raw materials, making them suitable only for high-grade concentrates. Low-grade fine ores are difficult to use due to low smelting efficiency and significant impurities, resulting in high raw material procurement costs and low resource utilization. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a large-scale energy-saving DC submerged arc furnace, which solves the problems of high power consumption, low power factor, and high raw material requirements of existing submerged arc furnaces.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a large-scale energy-saving DC submerged arc furnace, comprising a base plate and a fixed frame mounted on the base plate, a separation box fixedly connected to the fixed frame, two conical rods symmetrically installed inside the separation box and rotatably connected to the separation box, a feed inlet on the separation box, two protective plates fixedly connected to the inner wall of the separation box, the two protective plates being symmetrically distributed on both sides of the feed inlet, a rotating shaft rotatably connected between the two protective plates, a scraper plate fixedly connected to the outer wall of the rotating shaft, coil springs fixedly connected to both ends of the rotating shaft, the other end of the coil springs being fixedly connected to the inner wall of the separation box, a first separation hopper and a second separation hopper fixedly connected to one end of the separation box near the base plate, and automatic material sorting achieved by rotating the conical rods.

[0006] Preferably, a magnetic suction belt is rotatably connected between the two protective plates, and the magnetic suction belt is located above the conical rod. The two protective plates are fixedly connected to a slag discharge hopper at one end outside the separation box, and the slag discharge hopper is located below the magnetic suction belt.

[0007] Preferably, a heating furnace is fixedly connected to the upper surface of the base plate, and multiple airflow plates are uniformly fixedly connected to the bottom wall of the heating furnace. A guide pipe is fixedly connected between every two airflow plates, and a furnace cover is fixedly connected to the end of the heating furnace away from the base plate.

[0008] Preferably, a feed hopper is fixedly connected to the upper surface of the separation box, two crushing rollers are rotatably connected inside the feed hopper, a plurality of extrusion blocks are fixedly connected to the inner wall of the feed hopper, and the extrusion blocks are adapted to the crushing rollers. A discharge hopper is fixedly connected to the output end of the feed hopper, and the output end of the discharge hopper is connected to the feed port.

[0009] Preferably, the output end of the second separating bucket is fixedly connected to a second conveying pipe, and a return port is provided on the second conveying pipe. The second separating bucket and the second conveying pipe are connected through the return port.

[0010] Preferably, a first spiral conveying plate is rotatably connected inside the second conveying pipe, the output end of the second conveying pipe is fixedly connected to the first conveying pipe, a second spiral conveying plate is rotatably connected inside the first conveying pipe, an installation hole is provided on the first conveying pipe, a return pipe is fixedly connected inside the installation hole, and the output end of the return pipe is located above the feed hopper.

[0011] Preferably, a vertical rail is fixedly connected to the upper surface of the base plate, a lifting seat is slidably connected inside the vertical rail, an insulating plate is fixedly connected to the end of the lifting seat near the heating furnace, and a graphite electrode is fixedly connected to the insulating plate.

[0012] Preferably, a rectifier cabinet is fixedly connected to the upper surface of the base plate, the graphite electrode is slidably connected to the furnace cover, a short mesh is fixedly connected to the output end of the rectifier cabinet, and the rectifier cabinet and the graphite electrode are connected through the short mesh.

[0013] Preferably, a threaded rod is rotatably connected inside the vertical rail, and the threaded rod is threadedly connected to the lifting seat.

[0014] Preferably, the heating furnace is provided with a feed hole, and the output end of the first separating bucket is fixedly connected to a feed pipe, and the output end of the feed pipe is fixedly connected to the feed hole.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. In this invention, the particle size of the raw ore is controlled by crushing and extruding it. A scraper plate automatically levels the crushed raw ore, and a conical rod rotates to guide the movement of the raw ore. The particle size of the raw ore is automatically screened according to the spacing between the conical rods. A magnetic belt rotates to specifically remove ferromagnetic impurities, reducing wear on the electrodes and furnace lining. Materials with excessive particle size fall into the second separation hopper and are transported back to the feed hopper for crushing through the first and second conveying pipes. Small-diameter raw ore and flux are added in layers according to a certain ratio, and inert gas is introduced through the airflow plate in the heating furnace to enhance the stirring of the molten pool. This promotes full contact between the effective components in the low-grade raw ore and the flux, reduces the inhibitory effect of impurities on the reaction, avoids excessive or insufficient local reaction, improves the recovery rate of effective components, and enables the direct smelting of low-grade raw ore in the furnace.

[0017] 2. In this invention, alternating losses are eliminated by relying on a full DC architecture. Combined with a double-anti-star non-in-phase anti-parallel topology, the mutual cancellation of current and magnetic field significantly reduces hysteresis and eddy current losses in the copper tubes, thereby lowering the operating temperature of the copper tubes and extending their service life. By adopting a full DC power supply mode, reactive power losses caused by alternating magnetic fields are eliminated at their source. Simultaneously, the multi-pulse rectification design of the double-anti-star non-in-phase anti-parallel topology further optimizes the current waveform, reducing reactive power generation and eliminating the need for large-capacity reactive power compensation devices. This non-in-phase anti-parallel structure can shorten the short grid layout length, and due to the uniform current distribution, the cross-section of the short grid conductors can be appropriately reduced without the need for supporting heat dissipation pipes, thus reducing energy consumption and capital investment. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of a large-scale energy-saving DC submerged arc furnace according to the present invention;

[0019] Figure 2 This is a cross-sectional view of the heating furnace section of a large energy-saving DC submerged arc furnace according to the present invention.

[0020] Figure 3 This is a cross-sectional view of the vertical rail of a large energy-saving DC submerged arc furnace according to the present invention.

[0021] Figure 4 This is a cross-sectional view of the feed hopper of a large energy-saving DC submerged arc furnace according to the present invention.

[0022] Figure 5 This is a cross-sectional view of the separation box structure of a large energy-saving DC submerged arc furnace according to the present invention.

[0023] Figure 6 This is a schematic diagram of the structure at the rotating shaft of a large energy-saving DC submerged arc furnace according to the present invention.

[0024] Figure 7This is a cross-sectional view of the first conveying pipe of a large energy-saving DC submerged arc furnace according to the present invention.

[0025] In the diagram: 1. Base plate; 2. Rectifier cabinet; 3. Short mesh; 4. Heating furnace; 5. Vertical rail; 6. Fixing frame; 7. Separation box; 8. First conveying pipe; 9. Return pipe; 10. Insulating plate; 11. Rotating shaft; 12. Furnace cover; 13. Graphite electrode; 14. Airflow plate; 15. Threaded rod; 16. Lifting seat; 17. Feed hopper; 18. Crushing roller; 19. Discharge hopper; 20. Feed inlet; 21. Protective plate; 22. Conical rod; 23. Scraper plate; 24. First separation hopper; 25. Second separation hopper; 26. Slag discharge hopper; 27. Magnetic belt; 28. Coil spring; 29. ​​Second conveying pipe; 30. Feeding pipe; 31. Air guide pipe; 32. Return port; 33. First spiral conveying plate; 34. Second spiral conveying plate; 35. Mounting hole; 36. Feed hole; 37. Extrusion block. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] refer to Figures 1-7 The large-scale energy-saving DC submerged arc furnace shown includes a base plate 1 and a fixing frame 6 mounted on the base plate 1. A specific embodiment is shown below:

[0028] Example 1

[0029] A separation box 7 is fixedly connected to the fixed frame 6. A feed hopper 17 is fixedly connected to the upper surface of the separation box 7. Two crushing rollers 18 are rotatably connected inside the feed hopper 17. Multiple extrusion blocks 37 are fixedly connected to the inner wall of the feed hopper 17, and the extrusion blocks 37 are adapted to the crushing rollers 18. A discharge hopper 19 is fixedly connected to the output end of the feed hopper 17, and the output end of the discharge hopper 19 is connected to the feed inlet 20.

[0030] By feeding the raw ore into the feed hopper 17, the drive motor of the crushing roller 18 drives it to rotate. Under the combined action of the crushing roller 18 and the extrusion block 37, the raw ore is crushed into small-diameter mineral particles, which can promote the full contact between the effective components and flux in the low-grade raw ore and reduce the inhibitory effect of impurities on the reaction.

[0031] Example 2

[0032] Two conical rods 22 are symmetrically installed inside the separation box 7, and the conical rods 22 are rotatably connected to the separation box 7. The separation box 7 has a feed inlet 20. Two protective plates 21 are fixedly connected to the inner wall of the separation box 7. The two protective plates 21 are symmetrically distributed on both sides of the feed inlet 20. A rotating shaft 11 is rotatably connected between the two protective plates 21. A scraper plate 23 is fixedly connected to the outer wall of the rotating shaft 11. A coil spring 28 is fixedly connected to both ends of the rotating shaft 11. The other end of the coil spring 28 is fixedly connected to the inner wall of the separation box 7. A first separation hopper 24 and a second separation hopper 25 are fixedly connected to one end of the separation box 7 near the bottom plate 1. Automatic sorting of materials is achieved by rotating the conical rods 22.

[0033] The crushed ore raw materials are fed into the separation box 7 through the feed inlet 20. The drive motor of the conical rod 22 drives it to rotate. The diameter of the end of the conical rod 22 near the feed inlet 20 is much larger than the diameter of the other end of the conical rod 22, which facilitates the movement of the ore raw materials between the conical rods 22. The protective plate 21 is close to the outer wall of the conical rod 22. The crushed ore raw materials are flattened by the scraper plate 23. The pushing force of the conical rod 22 on the ore raw materials is greater than the elastic force of the coil springs 28 at both ends of the scraper plate 23. The scraper plate 23 only flattens the ore raw materials and does not affect the movement of the ore raw materials. The ore raw materials of different diameters are classified according to the spacing between the conical rods 22. The ore raw materials with smaller diameters fall into the first separation hopper 24, and the ore raw materials with larger diameters fall into the second separation hopper 25.

[0034] A magnetic suction belt 27 is rotatably connected between the two protective plates 21, and the magnetic suction belt 27 is located above the conical rod 22. The two protective plates 21 are fixedly connected to a slag discharge hopper 26 at one end outside the separation box 7, and the slag discharge hopper 26 is located below the magnetic suction belt 27.

[0035] Under the action of the aforementioned scraper plate 23, the crushed ore raw material is scraped flat. The drive motor of the magnetic belt 27 drives it to rotate. Multiple soft magnetic plates are evenly arranged on the outer wall of the magnetic belt 27, and each soft magnetic plate can work independently. When the magnetic belt 27 moves above the ore raw material, the soft magnetic plate near the ore raw material is automatically energized to generate magnetic force, which adsorbs the magnetic impurities in the ore raw material, reducing the wear on the electrodes and furnace lining. When the soft magnetic plate on the magnetic belt 27 moves above the slag discharge hopper 26, the soft magnetic plate is automatically de-energized and the magnetic force disappears. The magnetic impurities adsorbed on the soft magnetic plate fall into the slag discharge hopper 26 and are separated.

[0036] Example 3

[0037] A heating furnace 4 is fixedly connected to the upper surface of the base plate 1. Multiple airflow plates 14 are evenly fixedly connected to the bottom wall of the heating furnace 4. A guide pipe 31 is fixedly connected between every two airflow plates 14. A furnace cover 12 is fixedly connected to the end of the heating furnace 4 away from the base plate 1. A vertical rail 5 is fixedly connected to the upper surface of the base plate 1. A lifting seat 16 is slidably connected inside the vertical rail 5. A threaded rod 15 is rotatably connected inside the vertical rail 5, and the threaded rod 15 is threadedly connected to the lifting seat 16. An insulating plate 10 is fixedly connected to the end of the lifting seat 16 near the heating furnace 4. A graphite electrode 13 is fixedly connected to the insulating plate 10. A feed hole 36 is opened on the heating furnace 4. A feed pipe 30 is fixedly connected to the output end of the first separation bucket 24, and the output end of the feed pipe 30 is fixedly connected to the feed hole 36.

[0038] The small-diameter ore raw material that has been separated and entered into the first separation hopper 24 is fed into the heating furnace 4 through the feed pipe 30. The drive motor, matched with the threaded rod 15, rotates the rod, adjusting the position of the lifting seat 16, and consequently the position of the graphite electrode 13. The insertion depth of the graphite electrode 13 can be dynamically adjusted according to the reaction state within the heating furnace 4, concentrating energy in the core area of ​​the molten pool, reducing edge energy loss, and improving the energy utilization rate of the graphite electrode 13. Simultaneously, inert gas is introduced into the airflow plate 14 through the gas guide pipe 31. At low flow rates, the gas is in the form of tiny bubbles. Overflowing from the bottom of the furnace, the rising bubbles carry the surrounding molten liquid upwards, forming local convection, breaking up the stratification of the molten pool, promoting full contact between the effective components and flux in the low-grade ore, and reducing the inhibitory effect of impurities on the reaction. The furnace lining of the heating furnace adopts a three-layer composite structure. The outer insulation layer is made of nano-grade aluminum silicate fiber, and the inner corundum layer is made of silicon carbide wear-resistant particles, which can withstand high temperatures above 1800℃. At the same time, a heat dissipation buffer zone is set between the furnace lining and the furnace shell to reduce heat loss from the furnace surface, reduce the proportion of heat dissipation energy consumption of the furnace body, and further improve energy utilization efficiency.

[0039] A rectifier cabinet 2 is fixedly connected to the upper surface of the base plate 1. Graphite electrode 13 is slidably connected to furnace cover 12. A short mesh 3 is fixedly connected to the output end of the rectifier cabinet 2. The rectifier cabinet 2 and graphite electrode 13 are connected through the short mesh 3.

[0040] The rectifier cabinet 2 integrates a rectifier transformer. This integrated design reduces line losses. Rectifier cabinet 2 contains two sets of anti-star rectifier bridge arms, each consisting of six thyristors. The rectifier transformer provides precisely matched three-phase AC power to the two anti-star rectifier circuits. When the two circuits are connected to the three-phase AC power supply, the phase difference is strictly controlled to 30°. The circuits are connected in reverse parallel, and the currents flowing through the copper tubes in both circuits are equal in magnitude and opposite in direction, resulting in mutually canceling magnetic fields. This significantly reduces leakage flux, thereby reducing hysteresis and eddy current losses. Compared to traditional single-star topologies, this structure utilizes windings... The utilization rate is significantly improved, the current distribution is more uniform, and the current density of the copper tube is relatively reduced, fundamentally solving the problem of copper tube heating in the components and significantly reducing the operating temperature of the copper tube. The optimized topology improves rectification efficiency while reducing total circuit loss. Combined with the advantage of the DC architecture itself having no alternating loss, it provides core support for the goal of reducing overall power consumption by 20%. At the same time, the 12-pulse rectification design can reduce grid harmonic pollution and reduce harmonic content, eliminating the need for additional filtering devices and further improving the energy efficiency of the electrical system. The non-in-phase anti-parallel structure can shorten the short network layout length. In addition, due to the uniform current distribution, the cross-section of the short network conductor can be appropriately reduced, and no supporting heat dissipation pipes are required. The short network adopts a combination design of copper busbar and water-cooled cable. The copper busbar is made of T2 oxygen-free copper with a conductivity of ≥98%. The water-cooled cable uses highly flexible copper wire bundles with excellent heat dissipation performance, which can reduce the investment in the short network and form a complete current transmission link from rectifier cabinet 2 to short network 3 to graphite electrode 13, ensuring stable current delivery.

[0041] Example 4

[0042] The output end of the second separating hopper 25 is fixedly connected to the second conveying pipe 29. The second conveying pipe 29 has a return port 32. The second separating hopper 25 and the second conveying pipe 29 are connected through the return port 32. The first spiral conveying plate 33 is rotatably connected inside the second conveying pipe 29. The output end of the second conveying pipe 29 is fixedly connected to the first conveying pipe 8. The second spiral conveying plate 34 is rotatably connected inside the first conveying pipe 8. The first conveying pipe 8 has an installation hole 35. The return pipe 9 is fixedly connected inside the installation hole 35, and the output end of the return pipe 9 is located above the feed hopper 17.

[0043] The larger diameter ore particles separated above fall into the second separation hopper 25 and enter the second conveying pipe 29 through the output end of the second separation hopper 25. The drive motor of the first spiral conveyor plate 33 drives it to rotate, pushing the ore particles into the first conveying pipe 8. The drive motor of the second spiral conveyor plate 34 drives it to rotate. When the ore particles move to the mounting hole 35, they enter the return pipe 9 under the push of the second spiral conveyor plate 34. The diameter of the return pipe 9 is much larger than the diameter of the crushed ore particles. The ore particles are then transported back to the feed hopper 17 for further crushing through the inclined return pipe 9.

[0044] The working principle of this invention is as follows: Raw ore is fed into the feed hopper 17. Under the combined action of the crushing roller 18 and the extrusion block 37, the raw ore is crushed into small-diameter particles. The crushed raw ore is fed into the separation box 7 through the feed inlet 20. The scraper plate 23 flattens the crushed raw ore. Based on the spacing between the conical rods 22, raw ore of different diameters is classified. Smaller diameter raw ore falls into the first separation hopper 24, and larger diameter raw ore falls into the second separation hopper 25. Multiple soft magnetic plates are evenly arranged on the outer wall of the magnetic belt 27. When the magnetic belt 27 moves above the raw ore, the soft magnetic plates near the raw ore are automatically energized to generate magnetic force, attracting magnetic impurities in the raw ore. When the soft magnetic plates on the magnetic belt 27 move above the slag discharge hopper 26, the soft magnetic plates are automatically de-energized, the magnetic force disappears, and the magnetic impurities attracted by the soft magnetic plates fall into the slag discharge hopper 26 for separation. The small-diameter particles in the first separation hopper 24 are separated. Larger diameter ore raw materials are fed into the heating furnace 4 through the feed pipe 30. The insertion depth of the graphite electrode 13 is dynamically adjusted according to the reaction state in the heating furnace 4 to concentrate energy in the core area of ​​the molten pool. Inert gas is introduced into the airflow plate 14 through the gas guide pipe 31. As the bubbles rise, they drive the surrounding molten liquid to flow upward, forming local convection and breaking the stratification of the molten pool. The current is input into the short mesh 3 through the rectifier cabinet 2. Since the short mesh 3 is electrically connected to the graphite electrode 13, the current is stably delivered to the graphite electrode 13 through the short mesh 3. Larger diameter ore raw materials fall into the second separation hopper 25 and enter the second conveying pipe 29 through the output end of the second separation hopper 25. The first spiral conveying plate 33 rotates and pushes the ore raw materials into the first conveying pipe 8. The second spiral conveying plate 34 rotates and moves the ore raw materials to the mounting hole 35. Under its push, the ore raw materials enter the return pipe 9. The ore raw materials are transported back to the feed hopper 17 for further crushing through the inclined return pipe 9.

[0045] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A large-scale energy-saving DC submerged arc furnace, comprising a base plate (1) and a fixing frame (6) disposed on the base plate (1), characterized in that: A separation box (7) is fixedly connected to the fixed frame (6). Two conical rods (22) are symmetrically installed inside the separation box (7) and are rotatably connected to the separation box (7). A feed inlet (20) is opened on the separation box (7). Two protective plates (21) are fixedly connected to the inner wall of the separation box (7). The two protective plates (21) are symmetrically distributed on both sides of the feed inlet (20). A rotating shaft (11) is rotatably connected between the two protective plates (21). A scraper plate (23) is fixedly connected to the outer wall of the rotating shaft (11). A coil spring (28) is fixedly connected to both ends of the rotating shaft (11). The other end of the coil spring (28) is fixedly connected to the inner wall of the separation box (7). A first separation hopper (24) and a second separation hopper (25) are fixedly connected to one end of the separation box (7) near the bottom plate (1). Automatic sorting of materials is achieved by rotating the conical rod (22).

2. The large-scale energy-saving DC submerged arc furnace according to claim 1, characterized in that: A magnetic suction belt (27) is rotatably connected between the two protective plates (21), and the magnetic suction belt (27) is located above the conical rod (22). The two protective plates (21) are fixedly connected to a slag discharge hopper (26) at one end outside the separation box (7), and the slag discharge hopper (26) is located below the magnetic suction belt (27).

3. A large-scale energy-saving DC submerged arc furnace according to claim 1, characterized in that: A heating furnace (4) is fixedly connected to the upper surface of the base plate (1). Multiple airflow plates (14) are evenly fixedly connected to the bottom wall of the heating furnace (4). A guide pipe (31) is fixedly connected between every two airflow plates (14). A furnace cover (12) is fixedly connected to the end of the heating furnace (4) away from the base plate (1).

4. A large-scale energy-saving DC submerged arc furnace according to claim 1, characterized in that: The upper surface of the separation box (7) is fixedly connected to a feed hopper (17), and two crushing rollers (18) are rotatably connected inside the feed hopper (17). Multiple extrusion blocks (37) are fixedly connected to the inner wall of the feed hopper (17), and the extrusion blocks (37) are adapted to the crushing rollers (18). The output end of the feed hopper (17) is fixedly connected to a discharge hopper (19), and the output end of the discharge hopper (19) is connected to the feed inlet (20).

5. A large-scale energy-saving DC submerged arc furnace according to claim 4, characterized in that: The output end of the second separation bucket (25) is fixedly connected to the second conveying pipe (29), and the second conveying pipe (29) is provided with a return port (32). The second separation bucket (25) and the second conveying pipe (29) are connected through the return port (32).

6. A large-scale energy-saving DC submerged arc furnace according to claim 5, characterized in that: The second conveying pipe (29) is rotatably connected to the first spiral conveying plate (33), the output end of the second conveying pipe (29) is fixedly connected to the first conveying pipe (8), the first conveying pipe (8) is rotatably connected to the second spiral conveying plate (34), the first conveying pipe (8) is provided with an installation hole (35), the installation hole (35) is fixedly connected to the return pipe (9), and the output end of the return pipe (9) is located above the feed hopper (17).

7. A large-scale energy-saving DC submerged arc furnace according to claim 3, characterized in that: A vertical rail (5) is fixedly connected to the upper surface of the base plate (1), and a lifting seat (16) is slidably connected inside the vertical rail (5). An insulating plate (10) is fixedly connected to one end of the lifting seat (16) near the heating furnace (4), and a graphite electrode (13) is fixedly connected to the insulating plate (10).

8. A large-scale energy-saving DC submerged arc furnace according to claim 7, characterized in that: The upper surface of the base plate (1) is fixedly connected to the rectifier cabinet (2), the graphite electrode (13) is slidably connected to the furnace cover (12), the output end of the rectifier cabinet (2) is fixedly connected to the short mesh (3), and the rectifier cabinet (2) and the graphite electrode (13) are connected through the short mesh (3).

9. A large-scale energy-saving DC submerged arc furnace according to claim 8, characterized in that: The vertical rail (5) is rotatably connected to a threaded rod (15), and the threaded rod (15) is threadedly connected to the lifting seat (16).

10. A large-scale energy-saving DC submerged arc furnace according to claim 3, characterized in that: The heating furnace (4) is provided with a feed hole (36), and the output end of the first separation bucket (24) is fixedly connected to a feed pipe (30), and the output end of the feed pipe (30) is fixedly connected to the feed hole (36).

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