A device for smelting light-burned magnesium powder by longitudinal plasma

Abstract

A kind of plasma longitudinal smelting light burned magnesium powder device, including power supply system, furnace body, conducting cross arm, lifting mechanism, powder gas current-carrying electrode, powder gas feeding mechanism, composite base electrode.In smelting process, light burned magnesium powder is continuously injected into furnace body by raw material gas with certain pressure through powder gas current-carrying electrode, under the condition that direct current source is connected and loop is formed, plasma emitter is formed.Gas is ionized in the strong electric field between "powder gas current-carrying electrode" and "composite base electrode", releases huge energy, forms extremely high temperature "longitudinal plasma arc", light burned magnesium powder particles entering arc area fully contact with plasma, absorb a large amount of heat in millisecond level time, realize flash melting, double stirring mechanism synchronous operation of arc impact and electromagnetic stirring, can effectively promote melt pool composition homogenization, further optimize reaction environment, reach the purpose of reducing smelting power consumption, improve the quality of large crystal magnesium oxide.

Description

Technical Field

[0001] This utility model belongs to the technical field of large crystallizing magnesium oxide production equipment, and particularly relates to a plasma longitudinal smelting device for lightly calcined magnesium powder. Background Technology

[0002] The production of large-crystal magnesia is a key area in the magnesite industry with high energy consumption and a high dependence on energy. Currently, magnesite companies use three-phase AC furnaces to produce large-crystal magnesia. Lightly calcined magnesia powder in block form is fed into the furnace, and three electrodes are used for horizontal arc melting and crystallization. The crystal transformation of magnesia is achieved through high temperature. However, uneven temperature distribution, cold zones, and insufficient stirring during crystallization reduce impurity migration, thus affecting product quality. Dual-electrode DC smelting of lightly calcined magnesia powder has also been used in some companies, but it has not been widely adopted. Compared with three-phase AC, it is very similar in characteristics except for the power supply method. Traditional processes have poor applicability to powder materials. Under high-temperature conditions, the thermal stickiness of magnesia powder can obstruct the air permeability of the furnace bed, easily leading to material buildup and potentially inducing dangerous furnace eruptions such as molten metal splashing. The large-crystal magnesia field suffers from problems such as outdated equipment, unstable product quality, high energy consumption, and the inability to use powder materials.

[0003] Therefore, this utility model proposes a plasma longitudinal smelting device and method for lightly calcined magnesium powder to solve the problems mentioned in the background art. Utility Model Content

[0004] To address the technical problems raised in the background art, this utility model provides a plasma longitudinal smelting device for lightly calcined magnesium powder, which achieves the goals of reducing smelting power consumption and improving product quality by rapidly melting the powder and improving the uniformity of the molten pool.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A plasma longitudinal smelting device for lightly calcined magnesium powder includes a power supply system, a furnace body, a conductive cross arm, a lifting mechanism, a powder-gas current-carrying electrode, a powder-gas feeding mechanism, and a composite base electrode. The negative terminal of the power supply system is connected to the conductive cross arm. The powder-gas current-carrying electrode is longitudinally positioned above the furnace body and connected to the conductive cross arm. The lifting mechanism drives the conductive cross arm to move up and down. The powder-gas current-carrying electrode has a central channel, which is connected to the powder-gas feeding mechanism. The composite base electrode is connected to the bottom of the furnace body. The positive terminal of the power supply system is connected to the composite base electrode.

[0006] The power supply system includes a high-voltage power supply, a vacuum switch, a transformer, and a rectifier. The high-voltage power supply is connected to the input terminal of the vacuum switch, and the output terminal of the vacuum switch is connected to the high-voltage side of the transformer via a high-voltage bus. The low-voltage side of the transformer is then connected to the AC input terminal of the rectifier via a low-voltage bus, transmitting AC power to the rectifier, which then performs the AC to DC conversion. The output terminals of the rectifier are connected to a conductive crossarm via a water-cooled cable.

[0007] The powder-gas feeding mechanism includes a storage bin, a raw material gas source, a rotary feeder, a wear-resistant hard tube, and a wear-resistant soft tube. The discharge port of the storage bin is connected to the feed port of the rotary feeder. One side of the rotary feeder is connected to the wear-resistant hard tube, and the other side of the rotary feeder is connected to the raw material gas source. The other side of the wear-resistant hard tube is connected to the powder-gas current-carrying electrode through the wear-resistant soft tube.

[0008] The lifting mechanism is a lifting hydraulic cylinder.

[0009] The composite base electrode includes a working layer of graphite carbon bricks, a permanent layer of graphite carbon bricks, refractory ramming mix, and refractory bricks. The working layer of graphite carbon bricks is connected to the bottom of the furnace body, the permanent layer of graphite carbon bricks is connected to the bottom of the working layer of graphite carbon bricks, the permanent layer of graphite carbon bricks is connected to the positive terminal of the power supply system, the refractory bricks are built on the outside of the working layer of graphite carbon bricks and the permanent layer of graphite carbon bricks, and the refractory ramming mix is ​​filled between the working layer of graphite carbon bricks, the permanent layer of graphite carbon bricks, and the refractory bricks.

[0010] The furnace body is concentrically arranged on the upper end of the composite base electrode, and an insulating plate is provided between the furnace body and the composite base electrode.

[0011] Compared with existing technologies, the beneficial effects of this utility model are: 1) This utility model of plasma longitudinal smelting light calcined magnesium powder device is driven by electric field energy, combined with powder gas current-carrying electrode and pressurized gas to construct plasma emitter, and performs flash melting treatment on light calcined magnesium powder. With the DC smelting heat effect and high power factor characteristics, it finally achieves efficient smelting of light calcined magnesium powder, and achieves the goal of reducing smelting power consumption and improving product quality.

[0012] 2) High-efficiency purification is achieved through a progressive process of "flash melting - continuous pool formation - strong stirring optimization". The melting process of light-burned magnesium powder uses a plasma arc as the core heat source. The ultra-high temperature plasma arc instantaneously flash melts the continuously input light-burned magnesium powder. As the molten material continues to accumulate, a continuous molten pool is gradually formed in the reaction area. After the molten pool is formed, it will be subjected to a dual synergistic stirring effect. The plasma arc, with its strong kinetic energy, generates a vertical impact force from top to bottom on the molten pool to break the melt stratification. The electromagnetic force generated when the current passes through the molten pool drives the melt to form a horizontal circulation convection. The dual stirring constructs a comprehensive strong stirring system. The sufficient stirring can make the temperature field distribution of the molten pool more uniform, greatly reduce local cold zones to avoid the residue of unmelted particles, and accelerate the gasification and escape of internal gases or impurities. It also promotes the sedimentation and separation of denser impurities (such as iron oxides) to the bottom of the molten pool, ultimately improving the efficiency of gas and impurity removal and ensuring the purity and density of the product (such as large crystalline magnesium oxide).

[0013] 3) The composite electrode structure of the plasma longitudinal smelting light-burned magnesia powder device adopts a three-layer design, with each layer having a clear function and working in synergy: the outermost layer is a refractory brick layer, whose core function is to resist the high temperature inside the furnace, prevent the furnace bottom from being burned through, and reduce heat loss to the outside of the furnace, maintaining the temperature environment required for smelting inside the furnace; the middle layer is a refractory ramming material layer, whose density blocks the penetration of molten material in the molten pool into the furnace bottom, preventing damage to the furnace bottom structure due to erosion; the innermost layer is a composite electrode layer, which is further divided into upper and lower layers. The upper layer is the working layer that directly participates in smelting, and the lower layer is a permanent layer that provides basic support and conductivity. The bonding surfaces of the two layers are coated with conductive paste to reduce contact resistance and ensure stable current conduction. During long-term smelting, the upper working layer of the composite electrode will inevitably be eroded by high temperature and molten material. This structural design allows for the replacement of the damaged upper working layer without replacing the entire composite electrode, thus avoiding the resource waste caused by overall replacement. It not only meets the core requirements of burn-through prevention, penetration prevention, and stable conductivity, but also has the significant advantages of easy local electrode replacement and high resource utilization.

[0014] 4) This device can reduce the electricity consumption per unit of smelting by 10-15%, increase the yield of 97% high-crystalline magnesium oxide by 10%, and reduce the light-burned magnesium powder briquetting process. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a plasma longitudinal smelting device for lightly calcined magnesium powder.

[0016] Figure 2 This is a schematic diagram illustrating the principle of plasma formation by the powder gas carrier electrode of this utility model.

[0017] Figure 3 This is a flowchart of the smelting process of a plasma longitudinal smelting device for lightly calcined magnesium powder.

[0018] In the diagram: 1-Vacuum switch, 2-Transformer, 3-Rectifier, 4-Water-cooled cable, 5-Conductive crossarm, 6-Lifting hydraulic cylinder, 7-Wear-resistant hard pipe, 8-Wear-resistant hose, 9-Rotary feeder, 10-Storage bin, 11-Raw material gas source, 12-Powder gas carrier electrode, 13-Furnace body, 14-Insulation board, 15-Composite base electrode, 16-Molten powder, 17-Molten pool, 1201-Resin wear-resistant coating, 1202-Plasma jet, 1203-Strong magnetic field direction, 1204-Molten pool stirring direction, 1501-Working layer graphite carbon brick, 1502-Permanent layer graphite carbon brick, 1503-Refractory ramming mix, 1504-Refractory brick. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this utility model clearer, the following detailed description is provided in conjunction with embodiments. The specific embodiments described herein are merely illustrative of this utility model and are not intended to limit it. All reasonable variations are used to explain the content of this utility model.

[0020] like Figures 1-3 As shown, a plasma longitudinal smelting device for lightly calcined magnesium powder includes a power supply system, a furnace body 13, a conductive cross arm 5, a lifting mechanism, a powder-gas current-carrying electrode 12, a powder-gas feeding mechanism, and a composite base electrode 15. The negative terminal of the power supply system is connected to the conductive cross arm 5. The powder-gas current-carrying electrode 12 is longitudinally arranged above the furnace body 13 and connected to the conductive cross arm 5. The lifting mechanism drives the conductive cross arm 5 to move up and down. The powder-gas current-carrying electrode 12 has a central channel, which is connected to the powder-gas feeding mechanism. The composite base electrode 15 is connected to the bottom of the furnace body 13. The positive terminal of the power supply system is connected to the composite base electrode 15.

[0021] The power supply system includes a high-voltage power supply, a vacuum switch 1, a transformer 2, and a rectifier 3. The high-voltage power supply is connected to the input terminal of the vacuum switch 1, and the output terminal of the vacuum switch 1 is connected to the high-voltage side of the transformer 2 via a high-voltage bus. The low-voltage side of the transformer 2 is then connected to the AC input terminal of the rectifier 3 via a low-voltage bus, transmitting AC power to the rectifier 3, which then performs the AC to DC conversion. The output terminals of the rectifier 3 are connected to the conductive cross arm 5 via a water-cooled cable 4.

[0022] Equipped with a rectifier 3, the input AC power is converted into DC power. Compared to traditional AC power supply, DC mode avoids the arc instability problem caused by the zero-crossing point of AC voltage, and at the same time, it reduces heat loss by utilizing the concentrated characteristic of anode heat effect. The DC power converted by the rectifier 3 can also effectively improve the power factor, solving the pain points of low power factor and high energy waste in traditional AC power supply. The dual effect of improved power factor and reduced heat loss can significantly reduce energy consumption in the smelting process.

[0023] The powder-gas feeding mechanism includes a storage bin 10, a raw material gas source 11 (nitrogen, compressed air, or argon are all acceptable), a rotary feeder 6, a wear-resistant hard tube 8, and a wear-resistant flexible tube 7. The discharge port of the storage bin 10 is connected to the feed port of the rotary feeder 9. One side of the rotary feeder 9 is connected to the wear-resistant hard tube 8, and the other side of the rotary feeder 9 is connected to the raw material gas source 11. The other side of the wear-resistant hard tube 8 is connected to the powder-gas current-carrying electrode 12 through the wear-resistant flexible tube 7.

[0024] The pressurized raw material gas source 11 has a dual function: it provides power for the transportation of lightly calcined magnesium powder and provides the necessary conditions for the formation of plasma. At the same time, it can provide different plasma energies depending on the type of gas source.

[0025] The lifting mechanism is a lifting hydraulic cylinder 6. The lifting hydraulic cylinder 6 is located below the conductive cross arm 5 and is used to control the lifting and lowering of the conductive cross arm 5; the powder gas carrier electrode 12 extends into the furnace body 13 to realize the transportation of lightly calcined magnesium powder and plasma smelting.

[0026] When the powder gas carrier electrode 12 and the pressurized raw material gas are energized, they form a plasma emitter, which breaks the local temperature gradient of the traditional molten pool and generates a longitudinal plasma arc.

[0027] A resin-based functional coating is applied to the inner wall of the central channel of the powder gas carrier electrode 12 to protect the electrode.

[0028] The composite base electrode 15 includes a working layer graphite carbon brick 1501, a permanent layer graphite carbon brick 1502, refractory ramming mix 1503, and refractory brick 1504. The working layer graphite carbon brick 1501 is connected to the bottom of the furnace body 13, the permanent layer graphite carbon brick 1502 is connected to the bottom of the working layer graphite carbon brick 1501, the permanent layer graphite carbon brick 1503 is connected to the positive terminal of the power supply system, the refractory brick 1504 is built on the outside of the working layer graphite carbon brick 1501 and the permanent layer graphite carbon brick 1502, and the refractory ramming mix 1503 is filled between the working layer graphite carbon brick 1501 and the permanent layer graphite carbon brick 1502 and the refractory brick 1504.

[0029] The furnace body 13 is concentrically arranged on the upper end of the composite base electrode 15, and an insulating plate 14 is provided between the furnace body 13 and the composite base electrode 15.

[0030] A method for smelting light calcined magnesia powder using a plasma longitudinal smelting device specifically includes: starting power supply from a high-voltage power source, forming an electric arc between the lower end of the powder-gas-carrying electrode 12 and the graphite carbon brick 1501 in the working layer; at this time, light calcined magnesia powder is discharged from the discharge port of the storage silo 10; pressurized raw material gas source 11 provides kinetic energy; and the light calcined magnesia powder is sequentially transported to the furnace body 13 through the rotary feeder 9, the wear-resistant hard tube 8, the wear-resistant soft tube 7, and the central channel of the powder-gas-carrying electrode 12. The pressure at the outlet of the central channel of the gas-carrying electrode 12 is no less than 0.5 MPa, ensuring smooth material feeding. After the pressurized gas is ionized by the electric arc, it forms a plasma jet 1202. The plasma jet arc releases enormous energy instantaneously, performing flash melting of the light-burned magnesium powder. During this process, the thermal effect of the composite base electrode 15 (i.e., the anode) continues to act, keeping the molten pool 17 at the required high temperature range. The temperature increase significantly enhances the melting sufficiency of the light-burned magnesium powder, creating favorable conditions for subsequent crystallization. At the same time, the dual stirring mechanism of the electric arc impact and electromagnetic stirring of the molten pool 17 operates synchronously, stirring and melting the light-burned magnesium powder, which can effectively promote the homogenization of the melt composition, further optimize the reaction environment, and ultimately help form large crystals of magnesium oxide.

[0031] The particle size of the lightly calcined magnesium powder is 77-150 μm; the molten pool temperature can reach up to 3000℃, which is more conducive to the formation of large crystal magnesium oxide.

[0032] The system employs a dual stirring mechanism consisting of electric arc impact and electromagnetic stirring. The electric arc impact utilizes the energy fluctuations of the arc light to promote melt convection, while electromagnetic stirring uses magnetic force to drive the circulation of substances within the melt. A dynamic intelligent control system for the entire furnace monitors the furnace's internal dynamics in real time, and, in conjunction with the unit's intelligent feeding system and automatic electrode control system, adjusts the feeding rate and electrical parameters to ensure stable operation of the unit.

[0033] Lightly calcined magnesium powder (77-150μm) is precisely fed into the wear-resistant hard tube 8 through the rotary feeder 9. The other end of the wear-resistant hard tube 8 is connected to the raw material gas source 11. At the same time, the pipeline is equipped with a gas flow regulating valve, which can adjust the gas flow rate in real time to adapt to the process requirements.

[0034] The wear-resistant rigid tube 8 and the wear-resistant flexible tube 7 are precisely connected, and the wear-resistant flexible tube 7 is then sealed to the powder-gas current-carrying electrode 12, forming a complete path from material conveying to electrode feeding. This ensures that the mixture of lightly calcined magnesium powder and raw material gas is leak-free and without stagnation during transmission. The inner wall of the central hole channel of the powder-gas current-carrying electrode 12 is coated with a resin-based functional coating, which can resist wear to maintain the integrity of the electrode body structure and avoid current conduction deviation caused by electrode wear, thus ensuring stable current distribution.

[0035] The powder gas carrier electrode 12 is arranged longitudinally along the furnace body and precisely positioned at the center of the furnace body 13.

[0036] The process of transporting lightly calcined magnesium powder and forming the plasma arc follows a coherent logic of "energy transport - powder transport - gas ionization - energy release - powder heating". Lightly calcined magnesium powder is continuously injected into the furnace body 13 by pressurized gas through the central channel of the powder-gas carrier electrode 12. After the DC power supply is applied, the gas is ionized in the strong electric field between the "cathode" and "anode". The ionized gas becomes a plasma composed of electrons, ions, and neutral particles, simultaneously releasing enormous energy and forming a "longitudinal plasma arc" with extremely high temperature and brightness. The lightly calcined magnesium powder particles entering the arc region come into full contact with the plasma, absorbing a large amount of heat within milliseconds.

[0037] like Figure 2 As shown, the high-voltage power supply is connected to the input terminal of vacuum switch 1. Vacuum switch 1 controls the circuit's on / off state and provides short-circuit and overload protection. The output terminal of vacuum switch 1 is connected to the high-voltage side of transformer 2 via a high-voltage bus, transmitting the high-voltage electricity to transformer 2 for voltage reduction. The low-voltage side of transformer 2 is then connected to the AC input terminal of rectifier 3 via a low-voltage bus, transmitting the AC power to the rectifier, which then performs the AC to DC conversion.

[0038] The negative terminal of the rectifier 3 is connected to the tail end of the conductive cross arm 5 via a water-cooled cable 4, thereby achieving stable current transmission from the rectifier to the conductive cross arm 5. A lifting hydraulic cylinder 6 is installed below the conductive cross arm 5, which can flexibly adjust the height of the conductive cross arm 5 to meet the dynamic requirements of the conductive cross arm position under smelting conditions.

[0039] The material outlet of the storage silo 10 is connected to the inlet of the rotary feeder 9 via a flange. One side of the rotary feeder 9 is connected to the wear-resistant hard pipe 8, and the other side is connected to the raw material air source 11. The raw material air source 11 provides power for the lightly calcined magnesium powder, ensuring that the lightly calcined magnesium powder is smoothly transported along the pipeline, forming a complete raw material supply chain.

[0040] The outlet of the wear-resistant hard tube 8 and the inlet of the wear-resistant soft tube 7 are connected by a flange. The outlet of the wear-resistant soft tube 7 and the inlet of the wear-resistant hard tube embedded in the conductive cross arm 5 are connected by a flange. The inlet of the wear-resistant hard tube embedded in the conductive cross arm 5 is aligned with the center channel of the powder gas carrier electrode 12.

[0041] The powder gas carrier electrode 12 coincides with the center line of the furnace body 13 and the composite base electrode 14, forming a high-temperature plasma arc zone in the center of the furnace body.

[0042] The composite base electrode 15 serves as a load-bearing structure, providing installation support for the furnace body 13 and ensuring its stable installation. An insulating sleeve 14 is used at the intermediate connection point. The composite base electrode 15 consists of a multi-layer structure, including a working layer of graphite carbon bricks, a permanent layer of graphite carbon bricks, ramming mix, and refractory bricks. The composite base electrode 15 is connected to the positive terminal of the rectifier via a water-cooled cable.

[0043] The plasma longitudinal smelting light-burned magnesia powder unit uses a full-furnace dynamic intelligent control system. This system monitors the dynamics inside the furnace in real time and, in conjunction with the unit's powder and gas conveying and electrode automatic adjustment system, adjusts the feeding rate and power parameters to ensure stable operation of the unit, helping to reduce power consumption and improve the quality of light-burned magnesia powder.

[0044] The entire device works in tandem. Pressurized gas is ionized by an electric arc to form a plasma arc, which flash-melts the lightly calcined magnesium powder, making the calcined magnesium powder melt more fully. At the same time, due to the double stirring effect, the composition of the molten pool is more uniform, and the degassing and impurity removal effect is better, creating better conditions for the formation of large-crystal fused magnesia.

[0045] This invention relates to a plasma longitudinal smelting apparatus and method for lightly calcined magnesium powder, enabling direct smelting of lightly calcined magnesium powder and reducing the briquetting process. It can reduce smelting energy consumption, improve product quality, and achieve efficient utilization of powdered raw material resources.

[0046] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.

Claims

1. A plasma longitudinal smelting apparatus for lightly calcined magnesium powder, characterized in that, The system includes a power supply system, a furnace body, a conductive crossarm, a lifting mechanism, a powder-gas current-carrying electrode, a powder-gas feeding mechanism, and a composite base electrode. The negative terminal of the power supply system is connected to the conductive crossarm. The powder-gas current-carrying electrode is longitudinally positioned above the furnace body and connected to the conductive crossarm. The lifting mechanism drives the conductive crossarm to move up and down. The powder-gas current-carrying electrode has a central channel, which is connected to the powder-gas feeding mechanism. The composite base electrode is connected to the bottom of the furnace body. The positive terminal of the power supply system is connected to the composite base electrode.

2. The plasma longitudinal smelting apparatus for lightly calcined magnesium powder according to claim 1, characterized in that, The power supply system includes a high-voltage power supply, a vacuum switch, a transformer, and a rectifier. The high-voltage power supply is connected to the input terminal of the vacuum switch, and the output terminal of the vacuum switch is connected to the high-voltage side of the transformer via a high-voltage bus. The low-voltage side of the transformer is then connected to the AC input terminal of the rectifier via a low-voltage bus. The output terminal of the rectifier is connected to a conductive cross arm via a water-cooled cable.

3. The plasma longitudinal smelting apparatus for lightly calcined magnesium powder according to claim 1, characterized in that, The powder-gas feeding mechanism includes a storage bin, a raw material gas source, a rotary feeder, a wear-resistant hard tube, and a wear-resistant soft tube. The discharge port of the storage bin is connected to the feed port of the rotary feeder. One side of the rotary feeder is connected to the wear-resistant hard tube, and the other side of the rotary feeder is connected to the raw material gas source. The other side of the wear-resistant hard tube is connected to the powder-gas current-carrying electrode through the wear-resistant soft tube.

4. The plasma longitudinal smelting apparatus for lightly calcined magnesium powder according to claim 1, characterized in that, The lifting mechanism is a lifting hydraulic cylinder.

5. The plasma longitudinal smelting apparatus for lightly calcined magnesium powder according to claim 1, characterized in that, The composite base electrode includes a working layer of graphite carbon bricks, a permanent layer of graphite carbon bricks, refractory ramming mix, and refractory bricks. The working layer of graphite carbon bricks is connected to the bottom of the furnace body, the permanent layer of graphite carbon bricks is connected to the bottom of the working layer of graphite carbon bricks, the permanent layer of graphite carbon bricks is connected to the positive terminal of the power supply system, the refractory bricks are built on the outside of the working layer of graphite carbon bricks and the permanent layer of graphite carbon bricks, and the refractory ramming mix is ​​filled between the working layer of graphite carbon bricks, the permanent layer of graphite carbon bricks, and the refractory bricks.

6. A plasma longitudinal smelting apparatus for lightly calcined magnesium powder according to claim 1 or 5, characterized in that, The furnace body is concentrically arranged on the upper end of the composite base electrode, and an insulating plate is provided between the furnace body and the composite base electrode.

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