Multi-field synergistic regulation microwave plasma high-purity quartz sand purification device and process

Abstract

This invention discloses a microwave plasma high-purity quartz sand purification device and process with multi-field synergistic control, belonging to the field of microwave plasma mineral purification technology. This solution is applicable to microwave plasma purification furnaces with insulated and transparent reaction zones. Segmented electrode plates, elliptical magnetic mirror coils, a microwave absorption anti-reflection layer, and electromagnetic field shielding adjustment components are arranged outside the insulated and transparent reaction zone, forming a multi-field synergistic control structure. The elliptical magnetic mirror coils employ differentiated windings at the top and bottom, forming a relatively strong vertical gradient magnetic field at the bottom of the cavity. The main magnetic mirrors at both ends of the cavity and the auxiliary weak magnetic mirror in the middle are axially coordinated to construct a magnetic mirror constraint region that is strong at both ends and weak in the middle. This combination constrains plasma diffusion, which helps to prolong the contact time between active ions and quartz sand, optimizing the material contact state. The coordinated structure of multiple groups can optimize the plasma distribution at the feed inlet, and improve problems such as uneven local electromagnetic field distribution, standing wave superposition, and field strength distortion caused by multiple microwave feeds; the segmented electrode output adjustable gradient electrostatic field improves the electric field distribution near the Debye sheath layer of the tube wall, regulates the movement of charged ions, and reduces secondary pollution caused by metal ion adhesion; the microwave absorption anti-reflection layer weakens microwave reflection and reduces the coupling interference of alternating electromagnetic field on the magnetic mirror coil, making it suitable for continuous purification of high-purity quartz sand.

Description

Technical Field

[0001] This invention relates to the field of microwave plasma mineral purification equipment technology, specifically to a microwave plasma high-purity quartz sand purification device and process with multi-field synergistic control. Background Technology

[0002] In the case of multi-point microwave feeding in a long cavity, the cavity is prone to uneven distribution of local electromagnetic fields of multiple microwaves, superposition of standing waves, and distortion of field strength. The superposition of various distortions will affect the stability of plasma operation. At the same time, when the long cavity microwave plasma reaction equipment is working, the plasma density naturally decays along the cavity axis, and charged ions are prone to trajectory deviation when heated.

[0003] Conventional constant cross-section ring coils have limited ability to construct a magnetic field gradient in the vertical direction of the cavity, making it difficult to form an effective magnetic induction intensity difference in the upper and lower regions of the cavity, and also difficult to form a stable magnetic mirror constraint region with strong ends and weak middle in the axial direction; plasma glow is prone to deviate from the downward quartz sand material channel, plasma diffusion is not effectively constrained, and the residence time of fluorine and chlorine active ions is short, which is not conducive to the activation and removal of impurities in quartz sand.

[0004] Furthermore, when using a fixed voltage electrode structure, it is difficult to adapt to the differences in the electric field distribution of the sheath at different positions along the cavity axis, and it is also impossible to finely control the migration direction of cations and anions. The metal impurity ions generated by ionization are prone to re-attach to the surface of the quartz sand or penetrate into the crystal lattice, bringing the risk of secondary pollution. The single-layer magnetic permeable component also cannot simultaneously take into account both DC magnetic field conduction and alternating microwave shielding. There is still room for further optimization of the existing equipment. Summary of the Invention

[0005] To address the problems of insufficient plasma confinement, easy deviation of the glow region from the material channel, uneven local electromagnetic field distribution under multi-point microwave feeding, standing wave superposition and field strength distortion, difficulty in controlling the migration direction of charged ions, and the risk of secondary adhesion of metal impurity ions in existing long-cavity microwave plasma purification equipment, this invention provides a microwave plasma high-purity quartz sand purification device and process with multi-field synergistic control.

[0006] This invention enables the electric field, magnetic field, microwave field, and shielding structure to form a multi-field synergistic control system by working together through the insulated wave-transmitting reaction region, segmented adjustable gradient plates, elliptical magnetic mirror coils that can form a vertical asymmetric magnetic field, multi-segment magnetic mirror coil assemblies, microwave absorption anti-reflection layer, and electromagnetic field shielding adjustment components.

[0007] The present invention provides a microwave plasma purification process with multi-field synergistic control, comprising the following steps: Step S1, quartz sand raw material and activation mixed gas are respectively fed into the microwave plasma reaction chamber, and impurities in the quartz lattice are activated and ionized by microwave plasma; Step S2, a vertical asymmetric magnetic field is formed by differentially winding magnetic mirror coils, and a magnetic mirror constraint region with strong ends and weak middle is constructed by the main magnetic mirror coils at both ends of the chamber and the auxiliary weak magnetic mirror coil in the middle along the axis of the chamber. The vertical asymmetric magnetic field and the magnetic mirror constraint region synergistically constrain plasma diffusion, causing the plasma glow region to shift towards the quartz sand material passage area; Step S3, magnetic field adjustment and / or attenuation by alternating electromagnetic field shielding components are used. The microwave alternating electromagnetic field couples with the magnetic mirror coil, and a double-layer composite shielding structure can be formed by the magnetic shielding column and the copper shielding sleeve; in step S4, the segmented power supply unit supplies power to each plate independently, forming an adjustable gradient electrostatic field that varies along the material travel direction in the cavity, improving the electric field distribution near the Debye sheath layer of the tube wall, guiding the migration of anions and cations, and reducing the risk of metal cations reattaching to the quartz sand; in step S5, a microwave feed structure with adjustable position and tilt angle can be adopted as needed, and at least some of the auxiliary weak magnetic mirror coils are arranged in the axial section or adjacent section of the cavity where the microwave feed inlet is located, in conjunction with the microwave absorption anti-reflection layer to alleviate the uneven distribution of local electromagnetic fields, standing wave superposition and field strength distortion under multi-channel microwave feed.

[0008] This invention provides a microwave plasma purification device with multi-field coordinated control, comprising a microwave plasma reactor body, a feeding and discharging structure and airflow structure, a multi-segment magnetic mirror coil assembly, an elliptical magnetic mirror asymmetric winding structure, an electrode assembly and a segmented power supply unit, a microwave absorption anti-reflection layer, a magnetic field adjustment and / or alternating electromagnetic field shielding component, and an ion migration and airflow guiding structure. A reaction chamber is provided within the microwave plasma reactor body. At least the position corresponding to the electrode plate in the reaction chamber is an insulated and microwave-transparent reaction area, allowing the electric field and microwaves to pass through and couple into the cavity. The reactor body is provided with a quartz sand material inlet, a processed sand material outlet, an activation gas inlet, and a tail gas and metal impurity outlet channel. A gravity-driven downward conveying channel for the sand material is arranged inside the cavity, allowing the quartz sand material to pass through the plasma interaction area under gravity.

[0009] The reaction chamber is externally fitted with a multi-segment magnetic mirror coil assembly. This assembly includes a main magnetic mirror elliptical water-cooled excitation coil located at both ends of the chamber, and an auxiliary magnetic weakening mirror elliptical water-cooled excitation coil located in the middle of the chamber. The main magnetic mirror coil and the auxiliary magnetic weakening mirror coil cooperate along the axial direction of the chamber to form a magnetic mirror confinement region with strong ends and a weak middle, as well as a composite gradient DC static magnetic field. The main magnetic mirror coil and / or the auxiliary magnetic weakening mirror coil can be elliptical water-cooled coils, with the major axis of the ellipse arranged vertically along the chamber and the minor axis arranged horizontally along the chamber. The lower half of the coil is multi-layered, while the upper half is single-layered, resulting in a higher magnetic induction intensity in the lower part of the chamber than in the upper part, forming a vertical magnetic field gradient.

[0010] An electrode assembly is installed on the outside of the reaction chamber. The electrode assembly includes an upper negative high-voltage electrode and a lower positive high-voltage electrode arranged opposite each other. The electrode assembly is divided into multiple independent power supply sections along the cavity axis. Each section is connected to a segmented power supply unit, which uses multiple high-voltage DC power supplies and has current limiting protection, breakdown detection, and interlocking cutoff functions. A microwave absorption anti-reflection layer is installed on the side of the electrode assembly facing the reaction chamber. The microwave absorption anti-reflection layer can be a coating layer, a sintered layer, a composite liner, or a detachable module, used to weaken microwave reflection caused by the metal electrode and alleviate standing wave superposition and field strength distortion within the cavity.

[0011] A magnetic field adjustment and / or alternating electromagnetic field shielding component is provided between the magnetic mirror coil assembly and the reaction chamber. The component can be any one or more combinations of a magnetic shielding column, a magnetic sleeve, and a composite shielding layer. In a preferred structure, the magnetic shielding column is covered with a copper shielding sleeve, a water-cooled interlayer is provided between the copper shielding sleeve and the magnetic mirror coil, and a water-cooled heat insulation gap is provided between the coil and the magnetic shielding column.

[0012] In this invention, the elliptical magnetic mirror winding has multiple layers in the lower half and a single layer in the upper half. The difference in the number of layers creates a relatively strong vertical gradient magnetic field in the lower part of the cavity, which helps to shift the plasma glow region towards the material channel and prolong the contact time between active ions and quartz sand. The main magnetic mirror coils at both ends of the cavity and the auxiliary weak magnetic mirror coil in the middle are axially coordinated to form a magnetic mirror constraint region that is strong at both ends and weak in the middle, which helps to enhance the constraint on plasma diffusion. The magnetically conductive shielding pillars, combined with the semi-open copper shielding sleeve, form a double-layer composite shielding structure, which can attenuate the conduction of alternating microwaves towards the magnetic mirror coils while the auxiliary DC magnetic field acts on the cavity. It helps reduce coupling interference between microwaves and magnetic mirror coils; the outer side of the electrode plate is equipped with a microwave absorbing anti-reflection layer, which can weaken the reflected microwaves caused by the electrode plate and alleviate the uneven distribution of local electromagnetic fields, standing wave superposition and field strength distortion under multi-channel microwave feeding; the electrode plate is divided into multiple independent voltage regulation sections along the axial direction and forms a gradient electrostatic field, which helps to improve the electric field distribution near the Debye sheath layer of the tube wall, guide the migration of anions and cations, and reduce the risk of metal cations re-attaching to quartz sand; the electrode plate assembly, magnetic mirror coil assembly and shielding components are all external modular structures, which can be added to and modified existing microwave plasma purification equipment with insulating and transparent areas. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the overall structure of the device of the present invention; Figure 2 This is an axial sectional view of the cavity of the present invention; Figure 3 This is a schematic diagram of the electrode plate segmentation and segmented power supply structure of the present invention; Figure 4 This is a schematic diagram of the elliptical magnetic mirror coil and double-layer composite shielding structure of the present invention.

[0014] Explanation of reference numerals in the attached diagram: 1—Microwave plasma reactor body; 2—Insulated and microwave-transparent reaction zone; 3—Microwave feed inlet; 4—Activation gas inlet; 5—Tail gas and metal impurity discharge channel; 6—Quartz sand material inlet; 7—Processed sand material outlet; 8—Sand material gravity downward conveying channel; 9—Multi-segment magnetic mirror coil assembly; 10—Main magnetic mirror elliptical water-cooled excitation coil; 11—Auxiliary weak magnetic mirror elliptical water-cooled excitation coil; 12—Plasma glow region offset direction; 13—Electrode plate assembly; 14—Upper negative high-voltage electrode plate; 15—Lower positive high-voltage electrode plate; 16—Independent power supply section of electrode plate; 17—Segmented power supply unit; 18—Microwave absorption anti-reflection layer; 19—Magnetic shielding column; 20—Water-cooled heat insulation gap between coil and magnetic shielding column; 21—Migration direction of metal cations; 22—Migration direction of fluorine and chloride anions; 23—Diffusion direction of neutral free radicals; 24—Airflow direction inside the cavity; 25—Copper shielding sleeve. Detailed Implementation

[0015] The technical solution of the present invention will be further described below with reference to the accompanying drawings. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Equivalent substitutions and modifications made by those skilled in the art without departing from the spirit and substance of the present invention should all fall within the scope of protection of the present invention.

[0016] Combination Figure 1 This invention provides a microwave plasma high-purity quartz sand purification device with multi-field coordinated control, comprising a microwave plasma reactor body 1. A reaction chamber is provided within the microwave plasma reactor body 1, and an insulating and transparent reaction region 2 is formed within the reaction chamber at least corresponding to the position of the electrode assembly 13. The insulating and transparent reaction region 2 can be integrally formed using a high-transmittance, high-temperature resistant, corrosion-resistant, and electrically insulating medium such as quartz, alumina, or silicon nitride ceramic, or it can be formed by setting an insulating and transparent window, allowing the external electrode electric field and microwave energy to couple into the cavity.

[0017] Combination Figure 1 The microwave plasma reactor body 1 is equipped with a microwave feed inlet 3, an activation gas inlet 4, a tail gas and metal impurity discharge channel 5, a quartz sand material inlet 6, and a treated sand material discharge end 7. After entering the cavity through the quartz sand material inlet 6, the quartz sand material is conveyed downward along the sand material gravity conveying channel 8 through the plasma action area; the activation mixed gas enters the cavity through the activation gas inlet 4, and microwaves are fed in through the microwave feed inlet 3 to ionize the activation mixed gas and generate plasma; the treated sand material is discharged from the treated sand material discharge end 7, and the tail gas carrying metal impurities is discharged through the tail gas and metal impurity discharge channel 5.

[0018] Combination Figure 1 and Figure 2The reaction chamber is externally fitted with a multi-segment magnetic mirror coil assembly 9. The multi-segment magnetic mirror coil assembly 9 includes a main magnetic mirror elliptical water-cooled excitation coil 10 located at both ends of the chamber and an auxiliary weak magnetic mirror elliptical water-cooled excitation coil 11 located in the middle of the chamber. The main magnetic mirror elliptical water-cooled excitation coil 10 and the auxiliary weak magnetic mirror elliptical water-cooled excitation coil 11 are coupled along the axial direction of the chamber, forming a magnetic mirror confinement region with strong ends and a weak middle, and a composite gradient DC static magnetic field. This is used to confine plasma diffusion and helps to slow down the axial decay of plasma density within the long chamber.

[0019] Combination Figure 2 At least some of the auxiliary weak magnetic mirror elliptical water-cooled excitation coils 11 are arranged in the axial section of the cavity where the microwave feed inlet 3 is located or in its vicinity. This arrangement can be used to adjust the plasma distribution and local electromagnetic boundary conditions near the feed inlet, and, in conjunction with the microwave absorption anti-reflection layer 18, to alleviate the uneven distribution of local electromagnetic fields, standing wave superposition, and field strength distortion caused by multiple microwave feeds. Multi-channel microwave phase synchronization can be achieved by the built-in function of the supporting microwave equipment and is not an additional adjustment component required by this device. Figure 2 The offset direction 12 of the plasma glow region is used to indicate the tendency of the glow region to shift towards the quartz sand material passage area under the action of a vertical asymmetric magnetic field.

[0020] Combination Figure 2 and Figure 3 An electrode assembly 13 is disposed on the outer side of the reaction chamber. The electrode assembly 13 includes an upper negative high-voltage electrode 14 and a lower positive high-voltage electrode 15 arranged opposite each other. The electrode assembly 13 is divided into multiple independent power supply sections 16 along the axial direction of the chamber, and each independent power supply section 16 is connected to a segmented power supply unit 17. The segmented power supply unit 17 can use multiple high-voltage DC power supplies and has current limiting protection, breakdown detection, and interlocking cut-off functions.

[0021] Combination Figure 3 Multiple independently powered sections 16 can form electric field strength sections such as E1, E2, E3, and E4 along the material travel direction, and can satisfy the gradient relationship of E1 < E2 < E3 < E4. By independently adjusting the voltage of each section through the segmented power supply unit 17, an adjustable gradient electrostatic field can be formed inside the cavity to improve the electric field distribution near the Debye sheath layer of the tube wall and regulate the migration direction of charged ions inside the cavity. The overall polarity of the upper negative high-voltage plate 14 and the lower positive high-voltage plate 15 can be switched uniformly according to the working conditions to adapt to the migration regulation requirements of different charged ions.

[0022] Combination Figure 2 and Figure 3A microwave absorption antireflection layer 18 is provided on the side of the electrode assembly 13 facing the reaction cavity. The microwave absorption antireflection layer 18 can be a coating layer, a sintered layer, a composite liner, or a detachable module. It can be fixed to the side of the electrode facing the cavity by means of bonding, spraying, sintering, embedding, clamping, or detachable connection. It is used to absorb or attenuate the reflected microwaves caused by the metal electrode, and alleviate the superposition of standing waves and field strength distortion in the cavity.

[0023] Combination Figure 2 and Figure 4 A magnetic field conditioning and / or alternating electromagnetic field shielding component is provided between the magnetic mirror coil assembly 9 and the reaction cavity. In one embodiment, the magnetic field conditioning and / or alternating electromagnetic field shielding component includes a magnetically conductive shielding post 19. The magnetically conductive shielding post 19 is arranged close to the outer wall of the cavity, which can assist the DC static magnetic field generated by the magnetic mirror to act on the interior of the reaction cavity, while attenuating the coupling interference of the microwave alternating electromagnetic field to the working area of ​​the magnetic mirror coil.

[0024] Combination Figure 4 A copper shielding sleeve 25 can be wrapped around the outside of the magnetic shielding column 19. A water-cooled interlayer is provided between the copper shielding sleeve 25 and the elliptical water-cooled excitation coil 10 of the main magnetic mirror. A water-cooled heat insulation gap 20 is formed between the elliptical water-cooled excitation coil 10 of the main magnetic mirror and the magnetic shielding column 19. The copper shielding sleeve 25 has little influence on the DC static magnetic field and can utilize the skin effect to attenuate the alternating microwaves conducted towards the elliptical water-cooled excitation coil 10 of the main magnetic mirror. Figure 4 In the middle, the structural hierarchy can be understood as including, from the inside out, the magnetic shielding column 19, the copper shielding sleeve 25, the water-cooled heat insulation gap 20, and the main magnetic mirror elliptical water-cooled excitation coil 10.

[0025] Combination Figure 4 Both the main magnetic mirror elliptical water-cooled excitation coil 10 and the auxiliary weakening magnetic mirror elliptical water-cooled excitation coil 11 can adopt an elliptical water-cooled coil structure. The major axis of the ellipse is arranged vertically along the cavity, and the minor axis is arranged horizontally along the cavity. The lower half of the coil is multi-layered, and the upper half is single-layered, so that the magnetic induction intensity in the lower part of the cavity is higher than that in the upper part, forming a vertical magnetic field gradient. By adjusting the vertical dimension of the ellipse and the difference in the number of coil layers, the offset amplitude of the plasma glow region can be adjusted, which helps to reduce the risk of ion bombardment damage to the cavity.

[0026] Combination Figure 2 During the operation of the device, the metal cations generated by ionization can migrate along the metal cation migration direction 21 and be discharged with the tail gas; fluorine and chloride anions can accumulate in the material region along the fluorine and chloride anion migration direction 22; neutral free radicals can diffuse along the neutral free radical diffusion direction 23 and participate in the activation reaction of impurities on the surface of quartz sand and near the crystal lattice; the airflow inside the cavity flows along the airflow direction 24 inside the cavity to carry out reaction byproducts and metal impurity ions.

[0027] Based on the above-mentioned device structure, after the quartz sand raw material and the activated mixed gas are fed into the cavity, microwave ionization generates plasma; the elliptical magnetic mirror coil forms a strong vertical magnetic field in the lower part of the cavity through differentiated winding; at the same time, the elliptical water-cooled excitation coil 10 of the main magnetic mirror at both ends of the cavity and the elliptical water-cooled excitation coil 11 of the auxiliary weak magnetic mirror in the middle cooperate to form a magnetic mirror confinement region. The two work together to shift the plasma glow region towards the material channel and improve the material contact conditions; the segmented gradient electrostatic field adapts to the differences in the electric field distribution of the sheath at different positions along the cavity axis, and orderly guides the migration of anions and cations; the microwave absorption anti-reflection layer 18 and the copper shielding sleeve 25 work together to weaken the reflected microwave and alternating microwave coupling interference.

[0028] The following three typical operating conditions are given to illustrate the structural configuration of the device and the selection of typical operating parameters of the present invention, without limiting the scope of protection of the present invention. In actual operation, adjustments can be made according to the composition, particle size, throughput, activation mixed gas, microwave power, material residence time, feed point, and target purity requirements of the quartz sand raw material.

[0029] In a standard operating condition, the magnetic induction intensity of the primary magnetic mirror is 450 Gauss, and the magnetic induction intensity of the auxiliary weak magnetic mirror is 220 Gauss; the electric field strengths of the four segments of the electrode are 45 kV / m, 65 kV / m, 85 kV / m, and 105 kV / m respectively, with a voltage gradient of 20 kV / m; the operating temperature is 650℃. Under this condition, the effects of magnetic field confinement, electric field improvement of sheath distribution, and mitigation of microwave disturbances are relatively balanced, making it a suitable benchmark condition for routine production.

[0030] In a strongly constrained operating condition, the magnetic induction intensity of the main magnetic mirror is 580 Gauss, and the magnetic induction intensity of the auxiliary weak magnetic mirror is 260 Gauss; the field strengths of the four segments of the pole plate are 50kV / m, 70kV / m, 95kV / m, and 120kV / m respectively, with a voltage gradient of 22.5kV / m; the operating temperature is 680℃. Under this condition, the number of layers in the lower half of the coil winding can be set to be relatively large, the constraint capability of the magnetic mirror constrained region is strong, and it is suitable for operating conditions with high impurity content in raw materials or prominent multi-channel microwave disturbances.

[0031] Under a low-load operating condition, the magnetic induction intensity of the main magnetic mirror is 320 Gauss, and the magnetic induction intensity of the auxiliary weak magnetic mirror is 180 Gauss; the field strengths of the four segments of the electrode are 40kV / m, 55kV / m, 70kV / m, and 85kV / m respectively, with a voltage gradient of 15kV / m; the operating temperature is 620℃. This operating condition is suitable for lightweight production scenarios with low throughput, relatively few raw material impurities, or a limited number of microwave feed points.

[0032] When this device is in operation, first check the microwave plasma reactor body 1, the activation gas inlet 4, the exhaust gas and metal impurity outlet channel 5, the quartz sand material inlet 6, the processed sand material outlet 7, and the relevant sealing connection positions to ensure that the reaction chamber, microwave feed inlet 3, cooling water circuit, high voltage power supply, excitation power supply, gas supply and exhaust gas treatment system are in an operational state; then start the cooling system and inert gas replacement to establish the supply of activation mixed gas.

[0033] After cooling and atmosphere establishment, the multi-segment magnetic mirror coil assembly 9 can be activated to form a composite gradient DC static magnetic field and a magnetic mirror confinement region by the main magnetic mirror elliptical water-cooled excitation coil 10 and the auxiliary weak magnetic mirror elliptical water-cooled excitation coil 11. The segmented power supply unit 17 is activated to output a set voltage to each plate's independent power supply section 16, so that an adjustable gradient electrostatic field is formed in the cavity. Microwaves are then fed into the cavity through the microwave feed inlet 3 to ionize and activate the mixed gas to form plasma, and the quartz sand raw material enters from the quartz sand material inlet 6 and passes through the plasma action area along the sand material gravity downward conveying channel 8.

[0034] During operation, the magnetic field strength, electrode voltage, feed position, or feed angle can be adjusted according to the plasma state, exhaust gas conditions, material throughput, and microwave field stability. The gas stream containing impurities formed during the reaction is discharged through the exhaust gas and metal impurity outlet channel 5, and the treated quartz sand is collected at the treated sand discharge end 7. When shutting down, the microwave power, high-voltage electrode voltage, and excitation current can be reduced in a conventional and safe sequence, while maintaining inert gas purging and cooling to a safe state.

Claims

1. A microwave plasma purification device with multi-field coordinated control, comprising a microwave plasma reactor body, wherein a reaction chamber is provided within the reactor body, characterized in that: The reaction chamber has at least one insulating and microwave-transparent reaction region corresponding to the electrode plate. This region is configured such that electric fields and microwaves can pass through and couple into the interior of the chamber. An electrode plate assembly is located on the outside of the reaction chamber. This assembly is divided into multiple independent power supply sections along the axial direction. Each power supply section is connected to an independently regulated segmented power supply unit to form an adjustable gradient electrostatic field along the material travel direction, controlling the migration direction of charged ions within the chamber. A microwave absorption and anti-reflection layer is provided on the side of the electrode plate assembly facing the reaction chamber. A multi-segment magnetic mirror coil assembly is fitted outside the reaction chamber. This assembly includes main magnetic mirror coils located at both ends of the chamber and an auxiliary weak magnetic mirror coil located in the middle of the chamber. The main and auxiliary weak magnetic mirror coils are coupled along the axial direction of the chamber. A magnetic mirror confinement region with strong ends and weak middle and a composite gradient DC static magnetic field are formed; at least part of the auxiliary weak magnetic mirror coils are arranged in the axial section or adjacent section of the cavity where the microwave feed inlet is located, to adjust the plasma distribution and local electromagnetic boundary conditions near the feed inlet, and to improve the problems of uneven local electromagnetic field distribution, standing wave superposition, and field strength distortion caused by multiple microwave feeds; the magnetic mirror coil assembly forms a vertically asymmetric magnetic field, and the magnetic mirror confinement region confines plasma diffusion, causing the plasma glow region to shift towards the quartz sand material passage area; a magnetic field adjustment and / or alternating electromagnetic field shielding component is provided between the magnetic mirror coil assembly and the reaction cavity to attenuate the coupling interference of the microwave alternating electromagnetic field on the magnetic mirror coil and to assist the DC static magnetic field in acting into the interior of the reaction cavity.

2. The purification apparatus according to claim 1, characterized in that: The electrode assembly is arranged along the entire axial length of the reaction chamber.

3. The purification apparatus according to claim 1, characterized in that: The electrode assembly includes an upper electrode and a lower electrode arranged opposite to each other, with the upper electrode connected to the negative electrode and the lower electrode connected to the positive electrode.

4. The purification apparatus according to claim 1, characterized in that: The polarity of the electrode assembly can be switched uniformly to adapt to the migration and regulation requirements of different charged ions.

5. The purification apparatus according to claim 1, characterized in that: The microwave absorbing anti-reflection layer is a coating layer, a sintered layer, a composite liner, or a detachable module, and is fixed by means of bonding, spraying, sintering, embedding, clamping, or detachable connection; the microwave absorbing anti-reflection layer is made of microwave absorbing material that is resistant to high temperature and corrosive atmosphere.

6. The purification apparatus according to claim 1, characterized in that: The magnetic induction intensity of the main magnetic mirror coil is 300 to 600 Gauss, and the magnetic induction intensity of the auxiliary weak magnetic mirror coil is 30% to 70% of that of the main magnetic mirror coil.

7. The purification apparatus according to claim 1, characterized in that: The electric field strength within a single power supply section is 40–130 kV / m, and the electric field strength is lower than the gas discharge threshold under operating conditions.

8. The purification apparatus according to claim 7, characterized in that: The electric field voltage gradient between two adjacent power supply sections is 15–35 kV / m.

9. The purification apparatus according to claim 3, characterized in that: The distance between the upper and lower electrodes is set according to the size of the reaction chamber and the target electric field strength.

10. The purification apparatus according to claim 1, characterized in that: The main magnetic mirror coil and the auxiliary weak magnetic mirror coil are both independently powered, and the magnetic field strength is individually adjustable. An insulating isolation structure is set between the power supply sections of adjacent plates, and the edges of the plates are protected with insulated rounded corners.

11. The purification apparatus according to claim 1, characterized in that: The segmented power supply unit adopts multiple high-voltage DC power supplies and has current limiting protection, breakdown detection, and interlocking disconnection functions.

12. The purification apparatus according to claim 1, characterized in that: The magnetic field adjustment and / or alternating electromagnetic field shielding component is any one or more combinations of magnetic shielding pillars, magnetic sleeves, and composite shielding layers.

13. The purification apparatus according to claim 1, characterized in that: The main magnetic mirror coil and / or auxiliary weak magnetic mirror coil are elliptical water-cooled coils, with the major axis of the ellipse arranged vertically along the cavity and the minor axis arranged horizontally along the cavity. The lower half of the coil is multi-layered and the upper half is single-layered, so that the magnetic induction intensity in the lower part of the cavity is higher than that in the upper part, forming a vertical magnetic field gradient. The main magnetic mirror coil and the auxiliary weak magnetic mirror coil cooperate along the cavity axis to form a magnetic mirror constraint region with strong ends and weak middle. The magnetic mirror constraint region constrains plasma diffusion and deflects the plasma glow toward the material channel. The plasma glow deflection amplitude can be adjusted by adjusting the vertical dimension of the ellipse and the difference in the number of coil layers, which helps to reduce the risk of ion bombardment damage to the cavity.

14. The purification apparatus according to claim 1, characterized in that: The magnetic shielding column is covered with a copper shielding sleeve, and a water-cooled interlayer is provided between the copper shielding sleeve and the magnetic mirror coil. The copper shielding sleeve has little influence on the DC static magnetic field and utilizes the skin effect to attenuate the conduction of alternating microwaves to the magnetic mirror coil.

15. A high-purity quartz sand purification process using the purification apparatus described in any one of claims 1 to 14, characterized in that, Includes the following steps: S1. Quartz sand raw material and activated mixed gas are fed into the microwave plasma reaction chamber, where plasma is used to activate and ionize impurities within the quartz lattice. S2. A vertical asymmetric magnetic field is formed by differentially winding magnetic mirror coils. Simultaneously, the main magnetic mirror coils at both ends of the chamber and the auxiliary weak magnetic mirror coil in the middle work together to construct a magnetic mirror confinement region. These two elements synergistically confine plasma diffusion, causing the plasma glow to deflect towards the material channel. Shielding components weaken microwave alternating interference, and a segmented gradient electrostatic field improves the electric field distribution near the Debye sheath layer of the tube wall, guiding the directional migration of anions and cations and reducing the risk of secondary contamination of the quartz sand. A microwave feed structure with adjustable position and tilt angle, along with corresponding auxiliary weak magnetic mirror coils, optimizes the plasma distribution at the feed inlet, alleviating uneven distribution of local electromagnetic fields, standing wave superposition, and field strength distortion caused by multiple microwave paths. S3. A segmented power supply unit independently supplies power to each electrode, forming a gradient electrostatic field within the chamber. The electric field regulates the migration of charged ions, which, in conjunction with the plasma reaction, participate in the impurity activation and removal process.

16. The purification process according to claim 15, characterized in that: The activated mixed gas comprises one or more of an inert carrier gas, a fluorine-containing component, and a chlorine-containing component; the inert carrier gas is one or more of argon, nitrogen, and helium; the fluorine-containing component is one or more of hydrogen fluoride, ammonium fluoride, and ammonium hydrogen fluoride; and the chlorine-containing component is one or more of hydrogen chloride, chlorine, and ammonium chloride.

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