Magnesium smelting equipment and process based on microwave vacuum dynamic reaction system through silicothermic method

Abstract

The invention discloses a silicothermic magnesium smelting device and process based on a microwave vacuum dynamic reaction system. The silicothermic magnesium smelting device comprises a continuous feeding system, a microwave reaction cavity, a vacuum maintaining system, a gradient condensing device and an intelligent control system. Continuous feeding in the vacuum environment is achieved through the two-stage airlock and the ceramic spiral, and the productivity is improved by 40%; the uniformity of the microwave field is ensured through the multimode resonant cavity and the silicon carbide layer, and the temperature fluctuation is + / -10 DEG C; power-pressure-temperature coupling is optimized through an intelligent control system, and the power consumption per ton of magnesium is smaller than or equal to 6,500 kWh; by means of multi-parameter interlocking and redundancy design, the system failure rate is lower than that of a traditional process by 90%; according to the invention, through modular design and intelligent control, industrial upgrading of a silicothermic magnesium smelting process is realized, and an innovative solution is provided for green metallurgy.

Description

Technical Field

[0001] The present invention relates to the technical field of magnesium metal smelting, and in particular to silicon thermal magnesium smelting equipment and a process based on a microwave vacuum dynamic reaction system. Background Art

[0002] The existing magnesium smelting process has the following bottlenecks:

[0003] (1) Heat transfer limitation:

[0004] Traditional resistance heating furnaces have significant thermal gradient distribution. Take a Φ300×1500mm reduction tank as an example:

[0005] When the surface temperature is 1250℃, the tank core temperature is only 980℃, with a temperature difference of 270℃;

[0006] Material heat conduction rate: 5.2×10 -6 m 2 / s (measured value);

[0007] This results in the effective reaction volume accounting for less than 45%, and the heat loss of a single tank reaching 18.7kW.

[0008] (2) Reaction kinetics barriers:

[0009] There are multiple limitations to solid-state diffusion-dominated reaction processes:

[0010] The magnesium vapor partial pressure must be lower than the equilibrium pressure, P_eq = 1853 Pa at 1350°C;

[0011] The actual industrial system pressure fluctuation range is 800-1200Pa, which exceeds the allowable value by 4.6 times;

[0012] Reaction activation energy Ea = 280 kJ / mol (experimentally determined value).

[0013] (3) Energy efficiency structure imbalance:

[0014] An energy consumption audit of a magnesium plant with an annual output of 8,000 tons showed that:

[0015] Effective heat energy ratio: 29.4%;

[0016] Tank heat storage loss: 43.1%;

[0017] Flue gas waste heat loss: 27.5%;

[0018] The overall thermal efficiency is only 16.8%, far lower than the theoretical value of 32-38%.

[0019] The existing improved technology has the following defects:

[0020] The problem of insufficient penetration depth of 24 GHz millimeter wave (D_p=3.2 cm) has not been solved;

[0021] Due to the lack of a dynamic coordination mechanism in vacuum, the magnesium vapor partial pressure remains above the critical value;

[0022] The process was operated intermittently and continuous feeding and product collection were not achieved.

[0023] Therefore, it is an urgent problem for those skilled in the art to provide a method that can realize the industrial upgrading of the silicon thermal magnesium smelting process and provide innovative solutions for green metallurgy. Summary of the Invention

[0024] In view of this, the present invention provides a silicon thermal method magnesium smelting equipment and process based on a microwave vacuum dynamic reaction system; through the coupling control of microwave body heating and non-equilibrium vacuum environment, a fundamental improvement in reaction kinetics is achieved.

[0025] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0026] Silicon thermal magnesium smelting equipment based on microwave vacuum dynamic reaction system includes: continuous feeding system, microwave reaction cavity, vacuum maintenance system, gradient condensation device, intelligent control system; among them,

[0027] The continuous feeding system is the core of the system's material input, and it realizes continuous feeding in a vacuum environment through a double-stage air lock mechanism.

[0028] The microwave reaction cavity is designed as a multi-mode resonant cavity with two sets of phase-adjustable microwave emission units built in;

[0029] The vacuum maintenance system is composed of a front-stage mechanical pump, a Roots pump unit and a vacuum buffer tank, and is responsible for quickly establishing and dynamically maintaining the vacuum environment required for the reaction;

[0030] The gradient condensation device is a four-stage temperature-controlled crystallizer that introduces magnesium vapor from the reaction chamber into the condensation zone through differential pressure diversion;

[0031] The intelligent control system integrates temperature, pressure, and power multi-parameter interlocking modules, and realizes full-process automation through industrial PLC and SCADA systems.

[0032] Preferably, it also includes a circulating water cooling system, a magnetron, a magnesium vapor condensation crystallizer, an airtight conveying channel, a non-condensable gas exhaust port, and a continuous slag discharge system; wherein the airtight conveying channel includes a high-temperature resistant ceramic spiral and a double-gate air lock.

[0033] Preferably, the continuous feeding system is located at the left end of the equipment and is connected to the multi-mode resonant cavity through a flange; it is equipped with a high-temperature resistant ceramic spiral and a double-gate air lock to work together to ensure vacuum isolation of the material during transportation, with a leakage rate of less than 1×10 -4 Pa·m3 / s;

[0034] The microwave reaction cavity is centrally arranged, with a microwave emitting unit installed on the top of the cavity and the high-temperature resistant ceramic spiral at the bottom; the operating frequency is 2.45 GHz, and the single group power is 50 kW;

[0035] The vacuum maintenance system is located at the lower right and is connected to the multi-mode resonant cavity and the gradient condensation device through a DN150 pipe. The system leakage rate is <0.1 Pa·m 3 / s, to meet the needs of continuous production;

[0036] The gradient condensation device is located on the right side of the multi-mode resonant cavity, with four-stage condensers stacked vertically and the outlet connected to the magnesium ingot collection bin;

[0037] The intelligent control system is independently arranged on the left and interacts with each module via the EtherCAT bus.

[0038] Preferably, the high-temperature resistant ceramic spiral equipped in the continuous feeding system is made of Al2O3-ZrO2 composite material, with a temperature resistance of up to 1600°C, and can stably push 50×50×100mm dolomite-ferrosilicon blocks, with an adjustable feeding rate of 100-200 blocks / hour; the double-gate air lock is opened and closed by controlling the air pressure difference, alternately switching between the feeding and sealing states to avoid vacuum damage.

[0039] Preferably, the microwave emitting unit built into the microwave reaction cavity is equipped with a silicon carbide microwave enhancement layer with a thickness of 0.3±0.05mm and a dielectric constant of ε=8.2-8.6, which significantly improves the microwave energy efficiency utilization rate by more than 85%; the interior of the cavity is a Φ800×6000mm cylindrical structure, and the material passes through the microwave field evenly under the drive of the high-temperature resistant ceramic spiral to achieve body heating; the standing wave distribution is optimized by the phase adjuster to ensure that the temperature gradient in the cavity is ≤5℃ / m, and the reaction temperature is stabilized at 1250-1350℃.

[0040] Preferably, the initial pumping speed of the front stage mechanical pump of the vacuum maintenance system is 690m 3 / h, reducing the system pressure to 80Pa within 2 minutes; the Roots pump group operates in series with a pumping speed of 2000L / s, and the speed is adjusted in real time by the PID algorithm, with a pressure control accuracy of ±20Pa; the vacuum buffer tank balances pressure fluctuations to avoid magnesium vapor backflow.

[0041] Preferably, the temperature gradient of the gradient condensation device is 650°C → 450°C → 300°C → 150°C; the first-stage condenser is 316L stainless steel 20°C water-cooled, the second-stage is -15°C Hastelloy C276 ethylene glycol circulation, and the third-stage is -196°C copper-nickel-plated liquid nitrogen spray; the surface is sprayed with Al2O3 nano-coating with a thickness of 50μm, a roughness Ra of 0.8μm, and a crystallization rate of 5.8kg / (h·m 2 ), magnesium ingot purity ≥99.7%, Fe≤0.15%, Si≤0.08%; the condensers are connected by metal bellows to adapt to thermal expansion deformation.

[0042] Preferably, the temperature sensor in the intelligent control system is a K-type thermocouple with an accuracy of ±1°C, and 20 measuring points are arranged along the axial direction of the cavity; the pressure transmitter is PKR251 with a range of 0.1-1000Pa and real-time feedback of the vacuum degree; the microwave power is dynamically adjusted according to the reaction stage, 0-50kW / group; the system has a built-in pressure-temperature phase diagram database of 100-500Pa, 1100-1350°C, and a fuzzy PID algorithm is used to optimize the three-dimensional control surface, reducing power consumption per ton of magnesium by 12%, and the failure rate is <0.1 times / thousand hours.

[0043] The silicon thermal magnesium smelting process based on a microwave vacuum dynamic reaction system includes the following steps:

[0044] S1. The calcined magnesite and ferrosilicon powder were pressed into a porous block at a ratio of 1:0.7-1.1, with a porosity of 15-25%;

[0045] S2. Apply 2.45 GHz microwaves under 50-500 Pa vacuum and heat to 1250-1350 ° C within 10 minutes;

[0046] S3. Magnesium vapor is introduced into a gradient condenser via differential pressure diversion, with a temperature gradient of 650°C to 150°C.

[0047] S4. Real-time adjustment of power and pumping speed to obtain a three-dimensional control surface of system pressure, magnesium vapor partial pressure, and reaction temperature; construct a pressure-temperature phase diagram database, and apply a fuzzy PID algorithm to achieve real-time parameter optimization.

[0048] Compared with the prior art, the present invention has achieved the following technical effects:

[0049] (1) High efficiency and continuous operation: Double-stage air lock and ceramic screw realize continuous feeding in vacuum environment, increasing production capacity by 40%;

[0050] (2) Precise temperature control: The multi-mode resonant cavity and silicon carbide layer ensure the uniformity of the microwave field, with a temperature fluctuation of ±10°C;

[0051] (3) Energy saving and consumption reduction: The intelligent control system optimizes the power-pressure-temperature coupling, and the power consumption per ton of magnesium is ≤6,500kWh;

[0052] (4) Safe and reliable: With multi-parameter interlocking and redundant design, the system failure rate is 90% lower than that of traditional processes;

[0053] (5) Through modular design and intelligent control, the present invention realizes the industrial upgrading of the silicon thermal magnesium smelting process and provides an innovative solution for green metallurgy. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is a structural diagram of the device of the present invention. DETAILED DESCRIPTION

[0055] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0056] like Figure 1 As shown, the present invention discloses a silicon thermal method magnesium smelting equipment based on a microwave vacuum dynamic reaction system, comprising: a continuous feeding system, a microwave reaction cavity, a vacuum maintenance system, a gradient condensation device, and an intelligent control system; wherein,

[0057] Continuous feeding system: It is the core of the system's material input, and realizes continuous feeding in a vacuum environment through a double-stage air lock mechanism;

[0058] Microwave reaction cavity: It is a multi-mode resonant cavity design with two sets of phase-adjustable microwave emission units built in;

[0059] Vacuum maintenance system: It consists of a front-stage mechanical pump, a Roots pump unit, and a vacuum buffer tank, and is responsible for quickly establishing and dynamically maintaining the vacuum environment required for the reaction;

[0060] Gradient condensation device: It is a four-stage temperature-controlled crystallizer that introduces magnesium vapor from the reaction chamber into the condensation zone through differential pressure diversion;

[0061] Intelligent control system: Integrates temperature, pressure, and power multi-parameter interlocking modules, and realizes full process automation through industrial PLC and SCADA systems.

[0062] It also includes a circulating water cooling system, a magnetron, a magnesium vapor condensation crystallizer, an airtight conveying channel, a non-condensable gas exhaust port, and a continuous slag discharge system; among them, the airtight conveying channel includes a high-temperature resistant ceramic spiral and a double-gate air lock.

[0063] Continuous feeding system: Located at the left end of the equipment, it is connected to the multi-mode resonant cavity through a flange; it is equipped with a high-temperature resistant ceramic spiral and a double-gate air lock to work together to ensure vacuum isolation of the material during transportation, with a leakage rate of less than 1×10 -4 Pa·m 3 / s;

[0064] Microwave reaction cavity: Centrally arranged, with a microwave transmitting unit installed on the top of the cavity and a high-temperature resistant ceramic spiral at the bottom; the operating frequency is 2.45GHz, and the single group power is 50kW;

[0065] Vacuum maintenance system: Located in the lower right corner, connected to the multi-mode resonant cavity and gradient condensation device through a DN150 pipe. The system leakage rate is <0.1Pa·m 3 / s, to meet the needs of continuous production;

[0066] Gradient condensation device: Located on the right side of the multi-mode resonant cavity, the four-stage condenser is stacked vertically, and the outlet is connected to the magnesium ingot collection bin;

[0067] Intelligent control system: It is independently set on the left and interacts with each module through the EtherCAT bus.

[0068] The continuous feeding system is equipped with a high-temperature resistant ceramic spiral made of Al2O3-ZrO2 composite material, which can withstand temperatures of up to 1600°C. It can stably push 50×50×100mm dolomite-ferrosilicon blocks, and the feed rate is adjustable in the range of 100-200 blocks / hour; the double-gate air lock is opened and closed by controlling the air pressure difference, alternately switching between feeding and sealing states to avoid vacuum damage.

[0069] The microwave emission unit built into the microwave reaction cavity is equipped with a silicon carbide microwave enhancement layer with a thickness of 0.3±0.05mm and a dielectric constant of ε=8.2-8.6, which significantly improves the microwave energy efficiency utilization rate by more than 85%; the interior of the cavity is a Φ800×6000mm cylindrical structure, and the material passes through the microwave field evenly under the drive of high-temperature resistant ceramic spirals to achieve body heating; the standing wave distribution is optimized through the phase regulator to ensure that the temperature gradient in the cavity is ≤5℃ / m, and the reaction temperature is stabilized at 1250-1350℃.

[0070] The initial pumping speed of the front stage mechanical pump of the vacuum maintenance system is 690m 3 / h, reducing the system pressure to 80Pa within 2 minutes; the Roots pump groups operate in series with a pumping speed of 2000L / s, and the speed is adjusted in real time by the PID algorithm, with a pressure control accuracy of ±20Pa; the vacuum buffer tank balances pressure fluctuations to avoid magnesium vapor backflow.

[0071] The temperature gradient of the gradient condensation device is 650℃→450℃→300℃→150℃; the first stage condenser uses 316L stainless steel 20℃ water cooling, the second stage uses -15℃ Hastelloy C276 ethylene glycol circulation, and the third stage uses -196℃ copper-plated nickel liquid nitrogen injection; the surface is sprayed with Al2O3 nano-coating with a thickness of 50μm and a roughness of Ra=0.8μm, with a crystallization rate of 5.8kg / (h·m 2 ), magnesium ingot purity ≥99.7%, Fe≤0.15%, Si≤0.08%; the condensers are connected by metal bellows to adapt to thermal expansion deformation.

[0072] The temperature sensor in the intelligent control system is a K-type thermocouple with an accuracy of ±1°C, and 20 measuring points are arranged along the axial direction of the cavity; the pressure transmitter is PKR251, with a range of 0.1-1000Pa and real-time feedback of vacuum degree; the microwave power is dynamically adjusted according to the reaction stage, 0-50kW / group; the system has a built-in pressure-temperature phase diagram database of 100-500Pa, 1100-1350°C, and uses a fuzzy PID algorithm to optimize the three-dimensional control surface, reducing power consumption per ton of magnesium by 12%, and the failure rate is <0.1 times / 1,000 hours.

[0073] The present invention also discloses a silicon thermal magnesium smelting process based on a microwave vacuum dynamic reaction system, comprising the following steps:

[0074] S1. The calcined magnesite and ferrosilicon powder were pressed into a porous block at a ratio of 1:0.7-1.1, with a porosity of 15-25%;

[0075] S2. Apply 2.45 GHz microwaves under 50-500 Pa vacuum and heat to 1250-1350 ° C within 10 minutes;

[0076] S3. Magnesium vapor is introduced into a gradient condenser via differential pressure diversion, with a temperature gradient of 650°C to 150°C.

[0077] S4. Real-time adjustment of power and pumping speed to obtain a three-dimensional control surface of system pressure, magnesium vapor partial pressure, and reaction temperature; construct a pressure-temperature phase diagram database, and apply a fuzzy PID algorithm to achieve real-time parameter optimization.

[0078] Among them, the parameters of the microwave reaction cavity are shown in Table 1;

[0079] Table 1:

[0080] parameter Specification Operating frequency 2.45GHz±50MHz Output power 6×50kW (expandable) Waveguide configuration WR340 standard waveguide Standing Wave Ratio ≤1.25

[0081] The parameters of the vacuum maintenance system are shown in Table 2;

[0082] Table 2:

[0083] Components model parameter Foreline pump 2BE4-705 <![CDATA[Pumping speed 690m 3 / h]]> Roots pump unit ZJP-1200 Pumping speed 2000L / s Vacuum measurement PKR251 Measuring range 0.1-1000Pa

[0084] The parameters of the gradient condensation device are shown in Table 3;

[0085] Table 3:

[0086] Condensation stages Temperature range (℃) Material Cooling method Level 1 650-450 316L stainless steel Water cooling (20℃) Level 2 450-300 Hastelloy C276 Ethylene glycol circulation (-15℃) Level 3 300-150 Copper nickel plating Liquid nitrogen spray

[0087] Process implementation method:

[0088] 1. Raw material pretreatment specifications

[0089] (1) Particle size control:

[0090] Calcined magnesite: D90≤100μm (laser particle size analysis);

[0091] Ferrosilicon powder: D50 = 45 ± 5 μm (SEM verification);

[0092] (2) Compression molding:

[0093] Pressure range: 80-120MPa;

[0094] Block density: 2.9±0.1g / cm 3 ;

[0095] Porosity: 15-20% (determined by mercury intrusion porosimetry).

[0096] 2. Process

[0097] During the continuous feeding stage, preform blocks (size 50×50×100 mm, porosity 18.3%) were first delivered to the reaction chamber at a steady rate of 120 blocks / hour through a double-screw airtight feeding system driven by a servo motor. The double-stage air lock mechanism maintained vacuum isolation in the chamber, and the air lock leakage rate was strictly controlled to <1×10 -4 Pa·m 3 / s to ensure system pressure stability.

[0098] The dynamic power control strategy is adopted in the microwave heating stage: 18kW / m 3 The power density is increased rapidly, so that the material temperature is raised from room temperature to 800℃ at a rate of 400℃ / min, and then the power is gradually reduced to 12kW / m within 2-5 minutes. 3 , continuously heating to the target temperature of 1250℃. The constant temperature stage is controlled by an infrared thermometer and microwave power interlocking. The temperature fluctuation range is ≤±10℃ to avoid sintering of materials caused by local overheating;

[0099] During the vacuum reaction phase, pressure-stage control is implemented: the foreline mechanical pump is activated to rapidly pump the system pressure from atmospheric pressure to ≤100 Pa within 2 minutes. After entering the main reaction phase, the system switches to the Roots pumping unit, and the pumping speed is dynamically adjusted using a PID algorithm to maintain the reaction pressure within the optimized range of 150±20 Pa. The magnesium vapor is directed to the condensation zone at a flow rate of ≥8 m / s through a CFD-optimized flow guide structure (flow channel curvature radius R = 200 mm, surface roughness Ra = 0.8 μm) to avoid reoxidation caused by vapor stagnation.

[0100] Product collection stage: magnesium vapor enters a four-stage gradient condensation device (650℃→450℃→300℃→150℃), and the Al2O3 nano-coating (thickness 50μm) on the surface of Hastelloy C276 is used to promote heterogeneous nucleation, and the crystallization rate is stabilized at 4.2kg / (h·m 2 ), ultimately producing high-quality magnesium ingots with a purity of 99.6% (Fe ≤ 0.2%, Si ≤ 0.1%, as verified by ICP-MS), and a surface oxide layer thickness of <10μm (semi-quantitative XRD analysis). The entire process utilizes an intelligent control system that implements a closed-loop linkage between temperature, pressure, and power parameters. The single-batch production capacity is 1.2 tons, with an electricity consumption of 7,350kWh per ton of magnesium. The system's continuous operating stability reaches 98.7%.

[0101] Example 1: Basic parameter verification

[0102] During the raw material pretreatment phase, calcined magnesite (MgO content ≥ 95%) and ferrosilicon powder (median particle size D50 = 45 μm) were precisely mixed at a mass ratio of 1:0.8. The mixture was then pressed under high pressure at 100 MPa to form a dense block measuring 50 × 50 × 100 mm. The porosity, as measured by mercury intrusion porosimetry, was 18.3%, meeting the process requirement of 15-20%.

[0103] During the feeding and vacuum establishment phase, continuous feeding is achieved by alternately opening and closing the double-gate air lock, and the feeding rate is stably controlled at 120 pieces / hour. At the same time, the foreline mechanical pump quickly reduces the system pressure from atmospheric pressure to 80Pa within 2 minutes, creating a high vacuum environment for subsequent reactions.

[0104] During the microwave heating and reaction phase, a step-by-step power control strategy was adopted: 18kW / m 3 The power density rises rapidly to 800°C and then drops to 12kW / m2 within 2-5 minutes. 3 The power density is maintained to the target temperature of 1250°C. During this process, the Roots pumping unit adjusts the pumping speed in real time to accurately control the system pressure at 150±20Pa, and the magnesium vapor is efficiently transmitted at a flow rate of 8.2m / s (verified by CFD simulation);

[0105] During the product collection phase, magnesium vapor enters a four-stage gradient condensation system (temperatures are 650°C → 450°C → 300°C → 150°C) to achieve directional crystallization, ultimately obtaining a high-purity magnesium ingot with a purity of 99.6% (Fe≤0.2%, Si≤0.1%). The crystallization rate is stable at 4.2 kg / (h·m 2 ); This process ensures the synergistic improvement of reaction efficiency and product quality through parameter linkage optimization.

[0106] Example 2: High-capacity optimization

[0107] To improve production capacity and energy efficiency, this embodiment achieves optimization through three improvements:

[0108] In terms of microwave power improvement, three new sets of 50kW magnetrons have been added to increase the total power to 450kW and the power density to 22kW / m 3 At the same time, the use of a rotating resonant cavity (10 rpm) improves the uniformity of the microwave field by 20% (field intensity fluctuation < 5%); in the upgrade of the continuous feeding system, a double-helix ceramic pusher mechanism replaces the double-gate air lock, and the feeding rate is increased from 120 pieces / hour to 180 pieces / hour (leakage rate < 1×10 -5 Pa·m 3 / s), and introduced online laser particle size monitoring (accuracy ±1μm), to adjust the ratio of ferrosilicon powder and magnesite in real time (fluctuation <0.5%); in terms of condensation system strengthening, the surface of the Hastelloy C276 four-stage condenser is sprayed with Al2O3 nano-coating (thickness 50μm, roughness Ra = 0.8μm), and the crystallization rate is increased from 4.2kg / (h·m 2 ) increased to 5.8kg / (h·m 2 ), and at the same time, a waste heat recovery module is added to use waste heat to preheat the feed blocks (energy saving rate 12%).

[0109] In the specific implementation, the raw material pretreatment uses magnesite with MgO 95.2% and ferrosilicon powder with D50 = 42μm in a ratio of 1:0.75, and the porosity of the pressed block is 17.8%; the microwave reaction stage is optimized to a two-stage heating method - the initial 1.5 minutes are heated at 25kW / m 3 The power density was rapidly increased to 1000°C (at a rate of 400°C / min) and then switched to 15kW / m2 within 2.5 minutes. 3Maintaining 1250±5°C, the system pressure was stabilized at 130±10Pa, and the flow structure was optimized through CFD to increase the magnesium vapor flow rate to 11.3m / s. During the product collection phase, the four-stage condensation temperature was adjusted from 700°C to 500°C to 350°C to 200°C, shortening the directional crystallization time by 20%. The final magnesium ingot purity reached 99.7% (Fe≤0.15%, Si≤0.08%), with a surface oxide layer <10μm. Efficiency data showed that the single-pass processing capacity increased from 1.2 tons to 1.68 tons (+40%), power consumption per ton of magnesium decreased from 7,350kWh to 6,468kWh (-12%), and continuous operation time was extended from 8 hours to 72 hours (+800%), verifying the synergistic effect of high power density and dynamic thermal management.

[0110] Example 3: Low-grade raw material adaptation

[0111] In response to the smelting requirements of low-grade magnesite (MgO 88%), this embodiment achieves adaptation by adjusting process parameters: in the optimization of raw material pretreatment, 2% CaF2 is added as a flux, the ferrosilicon ratio is adjusted to 1:1.05 to compensate for the insufficient activity of the reducing agent, the pressing pressure is increased to 120 MPa, and the porosity is controlled at 20.5% (verified by mercury intrusion porosimetry); in terms of strengthening reaction conditions, the microwave power density is increased to 20 kW / m 3 (total power 360kW), the reaction temperature was raised to 1300±10℃, and the constant temperature time was extended to 15 minutes (online mass spectrometry was used to monitor changes in CO concentration); during vacuum dynamic regulation, the system pressure was reduced to 100±15Pa (the Roots pumping speed was increased by 30%), the magnesium vapor flow rate was stabilized at 9.5m / s, and a sulfur capture module (activated carbon fiber filter element) was added to reduce the sulfur content from 0.3% to 0.08%.

[0112] During the implementation process, low-grade magnesite with MgO 88.3% and CaO 4.1% was mixed with ferrosilicon powder with D50 = 50μm to form a block (porosity 20.2%). The microwave reaction stage was divided into two steps of temperature increase: 18kW / m 3 Heat up to 900℃, then switch to 22kW / m3 in the next 3 minutes 3 The process reaches a temperature of 1300°C, while simultaneously removing impurities by discharging 0.3kg of Fe-Si eutectic per hour through a side exhaust port. An electromagnetic separation unit is added to the product collection stage, achieving a separation efficiency exceeding 99%, resulting in a final magnesium ingot purity of 99.4% (Fe ≤ 0.25%, Ca ≤ 0.05%), meeting ASTM B92 standards. Performance data shows that despite a 7% reduction in raw material grade (MgO 95% → 88%), magnesium recovery remains at 94.6% (7.6% higher than the conventional process's 87%). Energy consumption per ton of magnesium increases to 8,120kWh (+10.5%), while sulfur impurity removal reaches 73.3%, demonstrating the process's high adaptability to low-grade resources.

[0113] The above description is merely a preferred embodiment of the present invention and does not limit the technical scope of the present invention. Therefore, any minor modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. Silicon thermal magnesium smelting equipment based on microwave vacuum dynamic reaction system, characterized in that: include: Continuous feeding system, microwave reaction chamber, vacuum maintenance system, gradient condensation device, intelligent control system; Among them, The continuous feeding system is the core of the system's material input, and it realizes continuous feeding in a vacuum environment through a double-stage air lock mechanism. The microwave reaction cavity is designed as a multi-mode resonant cavity with two sets of phase-adjustable microwave emission units built in; The vacuum maintenance system is composed of a front-stage mechanical pump, a Roots pump unit and a vacuum buffer tank, and is responsible for quickly establishing and dynamically maintaining the vacuum environment required for the reaction; The gradient condensation device is a four-stage temperature-controlled crystallizer that introduces magnesium vapor from the reaction chamber into the condensation zone through differential pressure diversion; The intelligent control system integrates temperature, pressure, and power multi-parameter interlocking modules, and realizes full-process automation through industrial PLC and SCADA systems.

2. The silicon thermal magnesium smelting equipment based on the microwave vacuum dynamic reaction system according to claim 1 is characterized in that: It also includes a circulating water cooling system, a magnetron, a magnesium vapor condensation crystallizer, an airtight conveying channel, a non-condensable gas exhaust port, and a continuous slag discharge system; wherein, the airtight conveying channel includes a high-temperature resistant ceramic spiral and a double-gate air lock.

3. The silicon thermal magnesium smelting equipment based on the microwave vacuum dynamic reaction system according to claim 1 is characterized in that: The continuous feeding system is located at the left end of the equipment and is connected to the multi-mode resonant cavity through a flange. It is equipped with a high-temperature resistant ceramic spiral and a double-gate air lock to work together to ensure vacuum isolation of the material during transportation, with a leakage rate of less than 1×10 - 4 Pa·m 3 / s; The microwave reaction cavity is centrally arranged, with a microwave emitting unit installed on the top of the cavity and the high-temperature resistant ceramic spiral at the bottom; the operating frequency is 2.45 GHz, and the single group power is 50 kW; The vacuum maintenance system is located at the lower right and is connected to the multi-mode resonant cavity and the gradient condensation device through a DN150 pipe. The system leakage rate is <0.1 Pa·m 3 / s, to meet the needs of continuous production; The gradient condensation device is located on the right side of the multi-mode resonant cavity, with four-stage condensers stacked vertically and the outlet connected to the magnesium ingot collection bin; The intelligent control system is independently arranged on the left and interacts with each module via the EtherCAT bus.

4. The silicon thermal magnesium smelting equipment based on the microwave vacuum dynamic reaction system according to claim 3 is characterized in that: The high-temperature resistant ceramic spiral equipped in the continuous feeding system is made of Al2O3-ZrO2 composite material, with a temperature resistance of up to 1600°C. It can stably push 50×50×100mm dolomite-ferrosilicon blocks, and the feeding rate can be adjusted in the range of 100-200 blocks / hour; the double-gate air lock is opened and closed by controlling the air pressure difference, alternately switching between the feeding and sealing states to avoid vacuum damage.

5. The silicon thermal magnesium smelting equipment based on the microwave vacuum dynamic reaction system according to claim 3, characterized in that: The microwave emission unit built into the microwave reaction cavity is equipped with a silicon carbide microwave enhancement layer with a thickness of 0.3±0.05mm and a dielectric constant of ε=8.2-8.6, which significantly improves the microwave energy efficiency utilization rate by more than 85%; the interior of the cavity is a Φ800×6000mm cylindrical structure, and the material passes through the microwave field evenly under the drive of the high-temperature resistant ceramic spiral to achieve body heating; the standing wave distribution is optimized by the phase regulator to ensure that the temperature gradient in the cavity is ≤5℃ / m, and the reaction temperature is stabilized at 1250-1350℃.

6. The silicon thermal method magnesium smelting equipment based on microwave vacuum dynamic reaction system according to claim 3 is characterized in that: The initial pumping speed of the front stage mechanical pump of the vacuum maintenance system is 690m 3 / h, reducing the system pressure to 80Pa within 2 minutes; the Roots pump group operates in series with a pumping speed of 2000L / s, and the speed is adjusted in real time by the PID algorithm, with a pressure control accuracy of ±20Pa; the vacuum buffer tank balances pressure fluctuations to avoid magnesium vapor backflow.

7. The silicon thermal magnesium smelting equipment based on the microwave vacuum dynamic reaction system according to claim 3, characterized in that: The temperature gradient of the gradient condensation device is 650°C → 450°C → 300°C → 150°C; The first stage condenser is 316L stainless steel with 20℃ water cooling, the second stage is -15℃ Hastelloy C276 ethylene glycol circulation, and the third stage is -196℃ copper nickel-plated liquid nitrogen spray; the surface is sprayed with Al2O3 nano-coating with a thickness of 50μm, a roughness of Ra=0.8μm, and a crystallization rate of 5.8kg / (h·m 2 ), magnesium ingot purity ≥99.7%, Fe≤0.15%, Si≤0.08%; the condensers are connected by metal bellows to adapt to thermal expansion deformation.

8. The silicon thermal magnesium smelting equipment based on a microwave vacuum dynamic reaction system according to claim 3, characterized in that: The temperature sensor in the intelligent control system is a K-type thermocouple with an accuracy of ±1°C, and 20 measuring points are arranged along the axial direction of the cavity; the pressure transmitter is PKR251, with a range of 0.1-1000Pa and real-time feedback of the vacuum degree; the microwave power is dynamically adjusted according to the reaction stage, 0-50kW / group; the system has a built-in pressure-temperature phase diagram database of 100-500Pa, 1100-1350°C, and uses a fuzzy PID algorithm to optimize the three-dimensional control surface, reducing power consumption per ton of magnesium by 12% and achieving a failure rate of <0.1 times / 1,000 hours.

9. A silicon thermal magnesium smelting process based on a microwave vacuum dynamic reaction system, characterized in that: The following steps are involved: S1. The calcined magnesite and ferrosilicon powder were pressed into a porous block at a ratio of 1:0.7-1.1, with a porosity of 15-25%; S2. Apply 2.45 GHz microwaves under 50-500 Pa vacuum and increase the temperature to 1250-1350 ° C within 10 minutes; S3. Magnesium vapor is introduced into a gradient condenser via differential pressure diversion, with a temperature gradient of 650°C to 150°C. S4. Real-time adjustment of power and pumping speed to obtain a three-dimensional control surface of system pressure, magnesium vapor partial pressure, and reaction temperature; construct a pressure-temperature phase diagram database, and apply a fuzzy PID algorithm to achieve real-time parameter optimization.

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