Vanadium-containing tailings comprehensive vanadium and iron recovery process by gravity separation

Abstract

This invention relates to the field of ore processing technology and discloses a comprehensive gravity separation process for recovering residual vanadium and iron from vanadium-bearing tailings. The process includes applying pulsed microwave irradiation to the raw vanadium-bearing tailings, utilizing the difference in dielectric loss to generate thermal stress and induce fission and separation. Under a weak reducing atmosphere, a reduction reaction is induced, causing hematite to transform into magnetite to increase its specific magnetization coefficient. The pretreated material is mixed with a pseudoplastic non-Newtonian fluid and pumped into a centrifugal separator. Under a weak, constant background magnetic field, vanadium-iron particles magnetically agglomerate, forming magnetic micro-agglomerates. These magnetic micro-agglomerates acquire settling momentum in the centrifugal force field, inducing localized high shear rates as they penetrate the non-Newtonian fluid, reducing the local apparent viscosity of the fluid and allowing them to enter the heavy product enrichment zone. Non-magnetic gangue is stably lifted by the high apparent viscosity fluid and discharged with the overflow. Finally, the gravity concentrate is collected, and the non-Newtonian fluid is recycled. This invention overcomes the technical defects of excessive grinding and separation loss of fine-grained minerals.

Description

Technical Field

[0001] This invention relates to the field of ore processing technology, specifically to a gravity separation process for recovering residual vanadium and iron from vanadium-containing tailings. Background Technology

[0002] In the field of mineral processing and secondary resource recycling, vanadium-bearing tailings are typically solid waste left over from vanadium extraction or iron ore beneficiation processes. Vanadium-bearing tailings contain fine-grained vanadium-bearing iron minerals with recycling value, as well as a large amount of gangue minerals, primarily aluminosilicates. To achieve comprehensive resource utilization, physical beneficiation processes are employed in engineering. Through liberation and hydrodynamic separation, vanadium-bearing iron minerals are separated from gangue minerals, thereby obtaining a concentrated concentrate enriched with both vanadium and iron.

[0003] Existing physical recovery processes for vanadium-bearing tailings typically employ a workflow consisting of mechanical grinding equipment combined with conventional gravity or magnetic separation equipment. In the material pretreatment stage, mechanical grinding equipment such as ball mills or tower mills is used to finely grind the vanadium-bearing tailings. The mechanical impact and friction applied by the grinding media reduce the particle size, promoting the physical separation of the target metallic minerals from the gangue matrix. Subsequently, the mechanically ground and liberated slurry is fed into a water-based gravity separator or magnetic separator, where the products are stratified and collected based on the inherent density or original magnetic differences between the minerals.

[0004] Existing recycling processes face a core technical contradiction when processing finely embedded vanadium-iron minerals: the conflict between the force mechanism of monomer liberation and the requirements for fine-particle separation. Mechanical crushing equipment applies volumetric force, which cannot identify the differences in bonding strength at mineral interfaces, preventing precise separation of vanadium-iron minerals along grain boundaries. To achieve the required degree of monomer liberation for subsequent physical separation, the mechanical grinding time or intensity must be indiscriminately increased. This directly leads to over-grinding of both gangue and target minerals, generating a large amount of non-selective fine-particle slime. Along with the decrease in particle size due to over-grinding, fine-grained vanadium-iron minerals retain their original weak magnetic state. In conventional water-based fluid media, the low settling momentum and weak magnetic response of these extremely small particles combine to make the target minerals easily lost in the tailings during the separation flow, making it difficult to construct effective stratified extraction conditions in the physical beneficiation process. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a comprehensive gravity separation process for recovering residual vanadium and iron from vanadium-bearing tailings, solving the problems mentioned in the background section. The process includes the following steps: In the pretreatment stage, the vanadium-bearing tailings of the raw ore are subjected to pulsed microwave irradiation under a weak reducing atmosphere. Based on the difference in dielectric loss parameters between the vanadium-bearing iron ore phase and the aluminosilicate gangue phase, the vanadium-bearing iron ore phase selectively absorbs microwave energy and converts it into a volumetric heat source internally. A temperature gradient and tensile-compressive combined thermal stress are generated at the interface between the vanadium-bearing iron ore phase and the aluminosilicate gangue phase. When the stress intensity factor determined by the tensile-compressive combined thermal stress exceeds the critical value of fracture toughness at the phase boundary, it induces the unstable propagation of micro-defects, forming microcracks and achieving mineral decomposition. Simultaneously, a gas-solid interface reduction reaction occurs between the reducing gas and the surface of the vanadium-bearing iron ore phase. By controlling the partial pressure ratio of carbon dioxide to carbon monoxide in the reaction system, the Gibbs free energy change corresponding to the driving force of the reduction reaction is kept negative, promoting the lattice reconstruction phase transition of hematite to magnetite and increasing the overall specific magnetization coefficient of the vanadium-bearing iron ore phase.

[0006] In the fluid preparation stage, a three-dimensional network structure was constructed in aqueous solution using macromolecular rheology modifiers to prepare a non-Newtonian fluid exhibiting pseudoplastic rheological characteristics. Based on the power-law fluid model, the apparent viscosity of the non-Newtonian fluid exhibits a negative exponential correlation with the shear rate it withstands. The non-Newtonian fluid displays a high apparent viscosity under low shear rate conditions, while the apparent viscosity decreases exponentially under high shear rate conditions.

[0007] During the sorting stage, pretreated materials are mixed with non-Newtonian fluid to form a slurry, which then enters the centrifugal separator. Under the influence of a weak, constant background magnetic field surrounding the sorting chamber, the magnetic dipole attraction generated between the vanadium-iron particles undergoing phase change surpasses the electrostatic repulsion of the double layer, disrupting the colloidal thermodynamic stability and causing the vanadium-iron particles to spontaneously aggregate into large-mass magnetic micro-agglomerates. These magnetic micro-agglomerates acquire centrifugal settling momentum in the centrifugal force field and induce localized high shear rates when penetrating the non-Newtonian fluid. The localized high shear rates reduce the apparent viscosity of the solid-liquid boundary layer region of the magnetic micro-agglomerates, decreasing fluid resistance and creating a positive feedback dynamic mechanism of localized shear force amplification and targeted viscosity reduction. The magnetic micro-agglomerates rapidly settle into the heavy product enrichment zone. The aluminosilicate gangue particles are non-magnetic and remain in a monomeric dispersion state. The centrifugal force and induced localized shear rates experienced by the aluminosilicate gangue particles are weak, and the high apparent viscosity maintained by the non-Newtonian fluid generates fluid drag, stably suspending the aluminosilicate gangue particles and allowing them to be discharged with the overflow.

[0008] In the product collection and recycling stage, the heavy product underflow undergoes mechanical extrusion to remove moisture and obtain gravity concentrate. The light product overflow is discharged into the static settling zone to eliminate directional shear stress. The polymer chains of the macromolecular rheology modifier re-intertwine and entangle, completing the physical reconstruction of the three-dimensional network structure and restoring a high apparent viscosity state. An inorganic coagulant is added to the static settling zone to compress the diffusion double layer thickness of the aluminosilicate gangue particles, causing the electrostatic repulsion potential energy between adjacent aluminosilicate gangue particles to decrease and become unable to resist the van der Waals attraction potential energy, resulting in a negative attraction state for the total interaction potential energy. The aluminosilicate gangue particles aggregate into large-sized flocs, complete sedimentation, and are discharged as tailings. The supernatant precipitates out and is recirculated to replenish the macromolecular rheology modifier before entering the formulation process for physical closed-loop recycling.

[0009] This invention provides a comprehensive gravity separation process for recovering residual vanadium and iron from vanadium-containing tailings. It offers the following advantages: 1. This invention introduces pulsed microwave irradiation under a weak reducing atmosphere during the pretreatment stage. Utilizing the difference in dielectric loss properties between the vanadium-bearing iron ore phase and the gangue phase, a local thermal stress gradient is constructed, inducing microcracks along grain boundaries to achieve selective pyrolysis of the minerals. This process avoids the fine-grained slime phenomenon produced by conventional mechanical crushing. The microwave hotspot effect catalyzes the lattice reconstruction phase transition from hematite to magnetite, increasing the overall specific magnetization coefficient of the vanadium-bearing iron ore phase and altering the physical and magnetic properties of fine-grained vanadium-bearing minerals. This establishes the physical conditions for the agglomeration and kinetic differentiation of mineral particles in the sorting process.

[0010] 2. This invention constructs a centrifugal sorting environment coupled with a weak, constant background magnetic field and a shear-thinning non-Newtonian fluid, driving vanadium-iron-containing particles with high specific magnetization to magnetically agglomerate into large-mass magnetic micro-aggregates. These magnetic micro-aggregates acquire centrifugal settling momentum in the centrifugal force field and induce locally high shear rates at the solid-liquid boundary layer, leading to a decrease in the apparent viscosity of the fluid and achieving targeted viscosity reduction. The low shear rate induced by the dispersed, non-magnetic gangue, coupled with the high apparent viscosity maintained by the non-Newtonian fluid, suppresses macroscopic fluid turbulence and stably suspends the gangue, thus completing the spatial stratification and isolation between the vanadium-iron-containing minerals and the gangue.

[0011] 3. This invention utilizes the three-dimensional spatial network structure reconstruction characteristics of non-Newtonian fluids under low shear rate conditions to restore the high apparent viscosity of the fluid medium during the static sedimentation process of light product discharge. Combined with the addition of an inorganic coagulant to compress the diffusion double layer thickness on the surface of gangue particles, the electrostatic repulsion potential energy is lower than the van der Waals attraction potential energy, driving the gangue particles to overcome fluid resistance and aggregate into flocs for sedimentation. The supernatant containing the rheology modifier is clarified, separated, and returned to the preparation process, achieving closed-loop recycling of the sorting medium and reducing external discharge losses. Attached Figure Description

[0012] Figure 1A flow chart of the gravity separation process for recovering vanadium and iron from residual vanadium in vanadium-bearing tailings; Figure 2 This is a flowchart of step S300 of the present invention. Detailed Implementation

[0013] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] Example: Please see the appendix Figure 1 -Appendix Figure 2 This invention provides a comprehensive gravity separation process for recovering vanadium and iron from residual vanadium in vanadium-containing tailings, comprising the following steps: S100: Microwave Selective Fracturing and Induced Magnetic Phase Transition. Vanadium-bearing tailings from the raw ore are continuously fed into a microwave reaction chamber. Under a protective atmosphere of a weakly reducing gas with a carbon monoxide volume fraction of 2% to 5%, pulsed microwave irradiation at a frequency of 2.45 GHz and a power density of 10 kW / t to 50 kW / t is applied, with the irradiation time controlled between 15 and 60 seconds. Utilizing the difference in dielectric loss parameters between the vanadium-bearing iron ore phase and the aluminosilicate gangue phase, the vanadium-bearing iron ore phase selectively absorbs microwave energy and heats up to 400°C to 600°C. The thermal stress gradient generated at the interface between the vanadium-bearing iron ore phase and the aluminosilicate gangue phase induces microcracks, achieving selective fracturing and separation of the vanadium-bearing tailings from the raw ore. The weakly reducing atmosphere combined with the microwave hotspot effect induces a solid-state reduction reaction on the surface of the vanadium-bearing iron ore phase, promoting a lattice reconstruction phase transition from hematite to magnetite, and increasing the overall specific magnetization coefficient of the vanadium-bearing iron ore phase. After pretreatment, the material is cooled to a temperature range of 80°C to 120°C and then discharged from the microwave reaction chamber. For the specific conveying action of the vanadium-containing tailings from the raw ore into the microwave reaction chamber, those skilled in the art can use a screw feeder for constant feeding. The conveying action of the vanadium-containing tailings from the raw ore is a well-known technology in this field and will not be described in detail here.

[0015] S200: Preparation of Shear-Thinning Non-Newtonian Fluid Medium. A macromolecular rheology modifier, such as anionic polyacrylamide with a molecular weight of 8 million to 12 million, is added to a solvent water at a mass concentration of 0.05% to 0.2%. The mixture is physically stirred with a variable frequency agitator to fully extend the hydrated segments of the macromolecular rheology modifier and form a network structure, thus preparing a non-Newtonian fluid with pseudoplastic rheological characteristics. Within the mass concentration range of 0.05% to 0.2%, the flow characteristic index n of the non-Newtonian fluid remains stable between 0.4 and 0.6. The non-Newtonian fluid exhibits a high apparent viscosity under static conditions or low shear rates, but its apparent viscosity decreases exponentially under high shear rate conditions. The prepared non-Newtonian fluid is continuously pumped to a centrifugal separator using a metering pump.

[0016] S300: Weak Magnetic Field Coupling Enhanced Centrifugal Separation. The pretreated material discharged from step S100 is mixed with the non-Newtonian fluid prepared in step S200 to prepare a slurry with a mass concentration of 15% to 30%, which is continuously pumped into the separation chamber of a centrifugal separator. A weak, constant background magnetic field with a strength of 0.05T to 0.15T is applied around the separation chamber. After the slurry enters the separation chamber, the vanadium-iron particles enhanced by microwave magnetic phase transition overcome electrostatic repulsion and magnetically agglomerate under the influence of the weak, constant background magnetic field, forming large-mass magnetic micro-agglomerates. Under the centrifugal force field of 60G to 120G generated by the high-speed rotation of the centrifugal separator, the large-mass magnetic micro-agglomerates acquire extremely high centrifugal settling momentum. When the magnetic micro-agglomerates penetrate the non-Newtonian fluid, a local high shear rate is induced at the solid-liquid boundary layer of the magnetic micro-agglomerates, leading to a decrease in the apparent viscosity of the non-Newtonian fluid in the local region of the solid-liquid boundary layer. The magnetic micro-agglomerates rapidly penetrate the non-Newtonian fluid layer and enter the heavy product enrichment zone. The non-magnetic fine-grained gangue remains in a monomeric dispersion state. Due to its small mass, the fine-grained gangue cannot disrupt the high-viscosity network structure of the non-Newtonian fluid. The fine-grained gangue is stably lifted by the non-Newtonian fluid and discharged with the overflow from the centrifugal sorting equipment.

[0017] S400: Product Collection and Closed-Loop Media Circulation. After the separation operation, the underflow concentrate is collected from the heavy product underflow outlet of the centrifugal separator. The underflow concentrate enters the solid-liquid separation process for moisture removal to obtain a gravity concentrate enriched with vanadium and iron. The light product discharged with the overflow enters the thickening settling tank. Under the low-shear static hydrodynamic environment inside the thickening settling tank, the disrupted rheological network structure inside the non-Newtonian fluid re-associates and restores a high apparent viscosity state. Polyaluminum chloride inorganic coagulant is added to the thickening settling tank at a dosage of 10 g / t to 30 g / t. The inorganic coagulant neutralizes the double-layer charge on the surface of the fine gangue, causing the fine gangue to overcome fluid resistance and flocculate and settle. The settled fine gangue is discharged from the thickening settling tank as the final tailings. The supernatant containing macromolecular rheology modifier overflowing from the top of the thickening settling tank is returned to the fluid medium preparation process via a pipeline system and reused as a base solvent in a closed-loop cycle. Regarding the specific compression control for dewatering the underflow concentrate, those skilled in the art can adjust the working pressure of the hydraulic pump according to the feed concentration. The control of dewatering the underflow concentrate is a well-known technique in the field and will not be elaborated upon here.

[0018] To specifically implement the selective fission and lattice reconstruction phase transition of the vanadium-bearing tailings in the aforementioned S100 ore, the specific process implementation of the microwave pretreatment stage is subdivided into the following steps: S101: Bed laying and wave transmission of vanadium-bearing tailings from raw ore.

[0019] The vanadium-bearing tailings from the raw ore are continuously laid into a smooth material bed with a thickness ranging from 20 mm to 50 mm. The smooth material bed is maintained at a constant speed of 0.5 m / min to 2.0 m / min for microwave transmission to ensure that microwave energy completely penetrates the depth of the smooth material bed.

[0020] S102: Multidimensional microwave irradiation and thermal stress-induced cracking.

[0021] Pulsed microwave irradiation at a frequency of 2.45 GHz and a power density of 10 kW / t to 50 kW / t was applied to a leveled material bed operating at a constant speed. Irradiation blind zones were eliminated by interleaved projection of multi-dimensional microwave electromagnetic fields. During pulsed microwave irradiation, different mineral phases within the leveled material bed exhibited differentiated microwave absorption and heating behaviors based on their dielectric properties. The microwave power density absorbed per unit volume of minerals was also measured. Determined by the following formula: Where f represents the microwave frequency, Represents the vacuum permittivity. The relative permittivity of the mineral is represented by E, and the microwave electric field strength is represented by E. Because the relative permittivity of the vanadium-bearing iron ore phase is much greater than that of the aluminosilicate gangue phase, microwave energy is selectively deposited within the vanadium-bearing iron ore phase, generating high temperatures and inducing localized thermal stress at the grain boundaries between the vanadium-bearing iron ore phase and the aluminosilicate gangue phase. Local thermal stress Characterized by the following formula: Where Y represents the composite Young's modulus, This represents the difference in the coefficient of thermal expansion between the vanadium-bearing iron ore phase and the aluminosilicate gangue phase. Represents the temperature gradient. Represents Poisson's ratio. When local thermal stress... When the bonding strength at the boundary between the vanadium-bearing iron ore phase and the aluminosilicate gangue phase exceeds the limit, microcracks initiation and propagation along the grain boundary are induced. During pulsed microwave irradiation, the leveled material bed is kept in a relatively static heated state without mechanical overturning, controlling the delamination boundary of the fracture.

[0022] S103: Construction of countercurrent weak reducing atmosphere and control of solid phase reduction.

[0023] While applying pulsed microwave irradiation, a weak reducing gas with a carbon monoxide volume fraction of 2% to 5% is continuously introduced. The flow direction of the weak reducing gas is controlled to be countercurrent with the movement direction of the leveling material bed. By adjusting the flow rate of the weak reducing gas, the environment of the leveling material bed is maintained at a slightly positive pressure of 50 Pa to 200 Pa, and the apparent contact residence time of the weak reducing gas inside the leveling material bed is controlled to be 10 to 30 seconds. The slightly positive pressure state prevents oxygen from the external environment from penetrating into the reaction environment. Under the coupling effect of a constant reducing atmosphere and microwave hotspot effect, the hematite phase on the surface of the vanadium-bearing tailings undergoes a local solid-phase reduction reaction, completing the lattice reconstruction phase transition to magnetite and increasing the specific magnetization coefficient of the vanadium-bearing iron phase. For the control of the excessive reaction of the vanadium-bearing iron phase entering the strong reducing state, those skilled in the art can adjust the carbon monoxide volume fraction in real time according to the reaction temperature feedback. The suppression and control of the excessive reduction reaction is a well-known technology in the art and will not be described in detail here.

[0024] The aforementioned step S102 summarizes the macroscopic physical operation of multidimensional microwave irradiation-induced thermal stress cracking. To support the subordinate technical features regarding selective dielectric heating and thermal stress cracking in the claims, the deep physical mechanism of thermal stress cracking induced by the microwave pretreatment stage is decomposed into the following specific evolutionary steps: S104: Construction of transient temperature gradient dominated by dielectric loss difference.

[0025] During the 15-60 second period of continuous pulsed microwave irradiation on a leveled material bed, the vanadium-bearing iron ore phase and the aluminosilicate gangue phase exhibited different heating rates due to differences in dielectric properties. The relative dielectric loss factor of the vanadium-bearing iron ore phase ranged from 0.1 to 0.5, while that of the aluminosilicate gangue phase was below 0.01. According to the microwave power absorption model, the pulsed microwave energy was converted into a volumetric heat source within the vanadium-bearing iron ore phase. The evolution of the three-dimensional transient temperature field within the heterogeneous mineral system composed of the vanadium-bearing iron ore phase and the aluminosilicate gangue phase followed the heat conduction control equation: in: Density representing the mineral phase, The specific heat capacity of the mineral phase is represented by T, the instantaneous temperature of the mineral phase is represented by t, the microwave irradiation time is represented by k, and the thermal conductivity of the mineral phase is represented by k. This represents the microwave power density absorbed per unit volume of mineral. For vanadium-bearing iron ore phases, the density of the vanadium-bearing iron ore phase is... The specific heat capacity of vanadium-bearing iron ore phase in the range of 4500 kg / m³ to 4800 kg / m³ In the range of 600 J / (kg·K) to 700 J / (kg·K), the thermal conductivity k of the vanadium-bearing iron ore phase is in the range of 5 W / (m·K) to 7 W / (m·K); for the aluminosilicate gangue phase, the density of the aluminosilicate gangue phase is... The specific heat capacity of the aluminosilicate gangue phase in the range of 2600 kg / m³ to 2800 kg / m³ The thermal conductivity k of the aluminosilicate gangue phase is in the range of 1.5 W / (m·K) to 2.5 W / (m·K) within the range of 800 J / (kg·K) to 900 J / (kg·K).

[0026] Substituting the above parameters into the heat conduction control equation, the temperature of the vanadium-bearing iron ore phase rises at a rate of 10°C to 50°C per second, reaching the range of 400°C to 600°C. This leads to the formation of the aluminosilicate gangue phase. With a thermal conductivity (k) approaching zero, the aluminosilicate gangue phase relies solely on boundary thermal conduction with the vanadium-bearing iron oxide phase to acquire heat. Due to the extremely low thermal conductivity (k) of the aluminosilicate gangue phase, heat cannot be rapidly dissipated into the deeper layers of the aluminosilicate gangue phase within a time window of 15 to 60 seconds. A temperature gradient of 100°C / mm to 300°C / mm eventually forms at the interface between the vanadium-bearing iron oxide phase and the aluminosilicate gangue phase.

[0027] S105: Critical thermal stress accumulation and microcrack instability propagation.

[0028] Temperature gradients induce a volume expansion tendency in the vanadium-bearing iron ore phase, which is rigidly constrained by the aluminosilicate gangue phase. This results in combined tensile and compressive thermal stresses at the interface between the vanadium-bearing iron ore and aluminosilicate gangue phases. When initial micro-defects exist at the interface, these combined thermal stresses concentrate at the tips of these micro-defects. The stress intensity factor at the tip of the micro-defect is... Based on fracture mechanics theory, it is determined by the following formula: Where: Y represents the defect shape coefficient. The value 'a' represents the localized thermal stress at the interface, and 'a' represents the characteristic size of the micro-defect. In vanadium-bearing tailings systems, the characteristic size 'a' of the micro-defect ranges from 1 micrometer to 5 micrometers.

[0029] With prolonged pulsed microwave irradiation time, local thermal stress An increase in stress intensity factor Increase. When the stress intensity factor Reaching and exceeding the critical value of fracture toughness at the mineral phase interface At this point, instability and propagation occur at the tip of the micro-defect, forming microcracks that penetrate the interface. The critical value of fracture toughness at the interface between the vanadium-bearing iron ore phase and the aluminosilicate gangue phase. Within the range of 0.8 MPa·m^(1 / 2) to 1.5 MPa·m^(1 / 2), microcracks extend along the weakest region of the bond between the vanadium-bearing iron ore phase and the aluminosilicate gangue phase, completing the physical decomposition of the vanadium-bearing iron ore phase. For the critical value of fracture toughness... For specific laboratory measurement methods, those skilled in the art can use the single-sided notched beam bending test for determination. The measurement of the critical value of fracture toughness is a well-known technology in this field and will not be described separately here.

[0030] Based on the reducing atmosphere established in step S103 and the high-temperature environment of 400℃ to 600℃ generated by microwave selective heating in step S104, the vanadium-bearing iron ore phase achieves monomer dissociation, while the weakly magnetic hematite component within the vanadium-bearing iron ore phase simultaneously undergoes a lattice reconstruction phase transition to the strongly magnetic magnetite component. The physicochemical mechanism of the targeted magnetic phase transition induced by the microwave pretreatment stage can be broken down into the following specific steps: S106: Local solid-phase reduction reaction catalyzed by microwave hotspot effect.

[0031] During pulsed microwave irradiation lasting 15 to 60 seconds, carbon monoxide gas infiltrates into the vanadium-bearing ore phase through a microcrack network generated in step S105. The mineral surface of the vanadium-bearing ore phase exposes a weakly magnetic hematite phase. The hematite phase undergoes a gas-solid interface reduction reaction with carbon monoxide at high temperatures ranging from 400°C to 600°C. The chemothermodynamic driving force of the gas-solid interface reduction reaction is determined by the Gibbs free energy change. The Gibbs free energy change is determined. Calculated using the following formula: in: This represents the change in Gibbs free energy under standard conditions. Here, T represents the ideal gas constant, and T represents the instantaneous absolute temperature at the gas-solid interface. This represents the partial pressure of carbon dioxide within the reaction system. This represents the partial pressure of carbon monoxide within the reaction system. The instantaneous absolute temperature T reaches above 673 K, and the partial pressure ratio is maintained by adjusting the volume fraction of carbon monoxide introduced. Within the range of 1.5 to 3.5. Under temperature conditions of 400℃ to 600℃, the partial pressure ratio is... A value between 1.5 and 3.5 ensures that the gas-solid interface reduction reaction remains strictly within the magnetite phase formation stage, preventing the vanadium-bearing ore phase from being over-reduced to non-magnetic aragonite or metallic iron. Substituting these parameter limits into thermodynamic formulas, the Gibbs free energy change is calculated. It shows a negative value. A negative Gibbs free energy change. The microwave radiation drives the removal of oxygen atoms from the hematite phase, and the micro-hotspot effect formed by the microwave radiation simultaneously reduces the activation energy required for the reduction reaction.

[0032] S107: Lattice reconstruction and specific magnetization transition.

[0033] As the reduction reaction at the gas-solid interface progresses, the removal of oxygen atoms from the hematite phase leads to crystal structure instability. The initial hexagonal crystal structure of the hematite phase undergoes localized spatial collapse, with iron and oxygen atoms rearranging within the lattice. The spatial structure of the hematite phase transforms into that of the magnetite phase, which has an inverse spinel structure, completing a lattice reconstruction phase transition. This lattice reconstruction phase transition directly alters the macroscopic magnetic properties of the vanadium-bearing iron ore phase. The overall specific magnetic susceptibility of the vanadium-bearing iron ore phase... The overall specific magnetic susceptibility is determined by the weighted average of the mass fractions of each component in the mineral system after the phase transition. Follow the following superposition formula: in: The mass fraction representing the residual hematite phase that has not undergone phase transformation. The specific magnetic susceptibility, representing the pure hematite phase. This represents the mass fraction of the newly formed magnetite phase. The specific magnetic susceptibility represents the pure magnetite phase. It is the overall specific magnetic susceptibility of the vanadium-bearing iron ore phase that has not undergone phase transformation before microwave pretreatment. Distributed in to Within the numerical range, it exhibits weak magnetism. Following localized solid-state reduction and lattice reconstruction phase transition, the mass fraction of the newly formed magnetite phase... The numerical value increases due to the specific magnetic susceptibility of the pure magnetite phase. The value is extremely high, and the overall specific magnetic susceptibility of the reconstructed vanadium-bearing iron ore phase is very high. leap to to Numerical range. The vanadium-bearing iron ore phase transforms from weakly magnetic to strongly magnetic. Strong magnetism provides the necessary magnetic parameters to support the subsequent magnetic agglomeration of the vanadium-bearing iron ore phase within a constant background magnetic field. For the determination of the kinetic parameters of the gas-solid interface reduction reaction, those skilled in the art can use a thermogravimetric analyzer to obtain isothermal weight loss curves for quantitative calibration. The determination of the kinetic parameters of the gas-solid interface reduction reaction is a well-known technique in this field and will not be described separately here.

[0034] Following the pretreatment process covered in S100, the vanadium-bearing tailings from the raw ore undergo microwave treatment to obtain a dissociated state and strong magnetic characteristics. To overcome the technical shortcomings of traditional water-based media, such as insufficient settling power of fine-grained minerals and susceptibility to turbulent flow, a separation medium with specific rheological properties is needed for the subsequent centrifugal separation process. The preparation and rheological control process of the shear-thinning non-Newtonian fluid medium in step S200 is broken down into the following specific steps: S201: Hydration stretching and network reconstruction of macromolecular rheology modifiers.

[0035] Industrial water was used as the base solvent, and its temperature was maintained between 20°C and 35°C. Anionic polyacrylamide with a molecular weight distribution between 8 million and 12 million was quantitatively added to the industrial water, controlling its mass concentration at 0.05% to 0.2%. The mixture was mechanically stirred at a speed between 50 and 150 rpm for 1 to 2 hours to avoid excessive mechanical shear force that could break the polymer backbone of the anionic polyacrylamide. Under the influence of hydration, the carboxyl anionic groups on the anionic polyacrylamide molecular chains ionized. The anionic groups carrying the same negative charge repelled each other, causing the coiled polymer chains of the anionic polyacrylamide to fully unwind within the industrial water. The unwinding long-chain molecules intertwined and entangled, constructing a three-dimensional network structure within the aqueous solution. This three-dimensional network structure physically impeded the flow of water molecules, transforming the prepared aqueous solution into a non-Newtonian fluid exhibiting pseudoplastic rheological characteristics.

[0036] S202: Physical quantification and parameter definition of constitutive equations for pseudoplastic fluids.

[0037] The rheological behavior of non-Newtonian fluids follows a power-law fluid model. Shear stress is generated within non-Newtonian fluids. With the shear rate it withstands The physical relationship between them is expressed by the following constitutive equation: in: The value represents the shear stress inside a non-Newtonian fluid, and K represents the consistency coefficient of the non-Newtonian fluid. represents the shear rate that a non-Newtonian fluid can withstand, and n represents the flow characteristic index of a non-Newtonian fluid.

[0038] Based on the above constitutive equation, the apparent viscosity of non-Newtonian fluids Expressed as: Within a mass concentration range of 0.05% to 0.2%, the three-dimensional spatial network structure constructed with anionic polyacrylamide resulted in a flow property index n distributed between 0.4 and 0.6, and a consistency coefficient K distributed between [missing value]. to The range. Since the flow property exponent n is strictly less than 1, the exponent term n-1 is always negative. Apparent viscosity. With shear rate It exhibits a negative exponential correlation. In static environments or with shear rates below [a certain value], [it shows a negative exponential correlation]. Under low shear rate conditions, the three-dimensional spatial network structure remains intact, and the apparent viscosity... Maintaining a high apparent viscosity allows for the suspension of fine-grained minerals and the suppression of fluid turbulence. When a localized fluid region experiences a viscosity higher than [a certain value], [this effect is achieved]. Under high shear rate conditions, polymer chain segments undergo directional alignment and deentanglement along the shear flow field direction, leading to an increase in the apparent viscosity of the non-Newtonian fluid. An exponential decrease occurs, exhibiting macroscopic mechanical properties of shear thinning. For specific laboratory measurement methods of the apparent viscosity and flow property index of non-Newtonian fluids, those skilled in the art can use a rotational rheometer to perform continuous variable shear scanning tests under isothermal conditions. The operation of the rotational rheometer is a well-known technique in the field and will not be described separately in this specification.

[0039] Following the microwave treatment in step S100 and the non-Newtonian fluid preparation in step S200, the pretreated material is mixed with the non-Newtonian fluid to prepare a slurry with a mass concentration of 15% to 30%. To impart settling momentum to the fine-grained vanadium-iron particles before the centrifugal separation process, the weak constant magnetic field coupling and magnetic micro-agglomeration mechanism in step S300 is decomposed into the following specific physical evolution steps: S301: Construction of a weak, constant background magnetic field environment and magnetic field intervention.

[0040] The slurry is continuously pumped into the sorting zone of the centrifugal separation process. A weak, constant background magnetic field with an intensity ranging from 0.05T to 0.15T is applied to the sorting zone, and the radial magnetic field gradient within the sorting zone is controlled to approach zero, forming a uniform magnetic field distribution environment. The magnetic field intensity of 0.05T to 0.15T causes the vanadium-iron-containing particles, which have undergone lattice reconstruction, to undergo magnetic polarization. The near-zero radial magnetic field gradient prevents the vanadium-iron-containing particles from undergoing macroscopic directional displacement and adsorption blockage under magnetic traction.

[0041] S302: The mechanical competition and evolution process of interparticle interaction forces.

[0042] When solid particles within the slurry enter a uniform, weakly constant background magnetic field, the magnetic domains within the vanadium-iron-containing microparticles align with the magnetic field lines, transforming the microparticles into magnetic dipoles with macroscopic magnetic moments. A magnetic dipole attraction then occurs between adjacent vanadium-iron-containing microparticles in a suspended state. Magnetic dipole attraction The physical quantity value is determined by the following formula: in: Represents the vacuum permeability. Represents the volume magnetic susceptibility of vanadium-containing iron particles. H represents the volume of a single vanadium-containing iron particle, H represents the magnetic field strength of a weak, constant background magnetic field, and d represents the center-to-center distance between adjacent vanadium-containing iron particles.

[0043] The initial characteristic particle size distribution of the vanadium-iron monomeric particles ranges from 5 micrometers to 20 micrometers. In non-Newtonian fluid media, hydrated ions are adsorbed on the surface of solid particles, forming an electric double layer structure. When adjacent vanadium-iron particles approach each other, electrostatic repulsion occurs within the electric double layer. The aluminosilicate gangue particles have not undergone microwave-induced magnetic phase transition, and their volumetric magnetic susceptibility is... Approaching zero, the magnetic dipole attraction force is calculated by substituting it into the formula. The numerical values ​​are small, and the electrostatic repulsion between the electric double layers of aluminosilicate gangue particles is greater than the attractive force of the magnetic dipoles, allowing the aluminosilicate gangue particles to remain in a monolithic dispersion state in the slurry. This, combined with the high volumetric magnetic susceptibility obtained in the aforementioned S100 step, contributes to this effect. Vanadium-containing iron particles in the 5- to 20-micrometer range induce magnetic dipole attraction. A sharp increase. A sharp increase in the magnetic dipole attraction. It surpasses the superposition resistance limit of the electrostatic repulsion of the double electric layer and the spatial steric hindrance of non-Newtonian fluids, breaking the colloidal thermodynamic stability of the slurry system.

[0044] S303: The formation of magnetic micro-agglomerates and the basic reconstruction of sedimentation momentum.

[0045] The attraction of magnetic dipoles drives adjacent vanadium-iron-containing particles to move in a directional manner and collide and adhere. A large number of monodisperse, fine-grained vanadium-iron-containing particles overcome the electrostatic energy barrier and spontaneously aggregate in a weak, constant background magnetic field. These monodisperse fine-grained vanadium-iron-containing particles combine and aggregate to form magnetic micro-aggregates with an equivalent diameter distribution ranging from 50 to 150 micrometers. The effective mass of these magnetic micro-aggregates is 15 to 400 times that of the monodisperse vanadium-iron-containing particles. This mass reconstruction enables the magnetic micro-aggregates to acquire centrifugal sedimentation momentum in a subsequent high-speed rotating centrifugal force field, establishing the physical condition for the magnetic micro-aggregates to overcome the high apparent viscosity network of non-Newtonian fluids by relying on locally high shear rates.

[0046] After assembling and effectively amplifying the magnetic micro-agglomerates in step S303, the solid particles with varying masses face a dynamic evolution path of differentiation within the internal flow field of the centrifugal sorting process. To support the technical characteristics of local shear force self-amplification, targeted viscosity reduction, and product stratification in the core centrifugal sorting process enhanced by weak magnetic field coupling, the deep dynamic process of the centrifugal sorting process is subdivided into the following physical steps: S304: Positive feedback dynamics of centrifugal sedimentation momentum amplification and targeted viscosity reduction.

[0047] A slurry containing solid particles of varying masses is subjected to centrifugal forces ranging from 60G to 120G within a centrifugal separation flow field. The radial centrifugal force experienced by the solid particles in this field is... Determined by the following kinetic formula: in: R represents the effective mass of the solid particles, and R represents the radius of gyration within the centrifugal separation flow field. The value of R is distributed in the range of 0.2 meters to 0.5 meters. Represents the angular velocity of the centrifugal sorting process. The values ​​range from 35 rad / s to 75 rad / s.

[0048] The magnetic micro-aggregates induced by the weak, constant background magnetic field, combined with the effective mass amplification of 15 to 400 times obtained in step S303, generate increased radial centrifugal force. Radial centrifugal force This induces radial settling velocities in the range of 0.05 m / s to 0.2 m / s for the magnetic micro-aggregates. When magnetic micro-aggregates settle at a radial velocity... When penetrating non-Newtonian fluid media, the solid-liquid boundary layer of magnetic micro-aggregates induces local shear rates. Local shear rate The physical quantity value is expressed by the following formula: in: The radial settling velocity representing the magnetic micro-aggregates, The equivalent diameter represents the magnetic micro-aggregates. Substituting the lower limit of sedimentation velocity (0.05 m / s) and the lower limit of the equivalent diameter (50 μm) into the local shear rate formula, the calculated local shear rate is... Breakthrough as defined in step S202 High shear rate threshold. This refers to the local shear rate. Substituting into the non-Newtonian fluid apparent viscosity formula established in step S202, the apparent viscosity of the non-Newtonian fluid in the local region surrounding the magnetic micro-aggregates decreases exponentially. This decrease in apparent viscosity leads to a simultaneous reduction in the fluid resistance exerted by the non-Newtonian fluid on the magnetic micro-aggregates, and this reduced fluid resistance further promotes radial settling velocity. Increase, radial settlement velocity Increase the local shear rate again The aforementioned physical processes establish a positive feedback dynamic mechanism around the magnetic micro-aggregates, characterized by localized shear force amplification and a continuous decrease in apparent viscosity. This positive feedback dynamic mechanism enables the magnetic micro-aggregates to rapidly penetrate the non-Newtonian fluid layer, achieving targeted viscosity reduction, and ultimately entering the heavy product enrichment zone of the centrifugal sorting area.

[0049] S305: The product stratification process of anti-turbulent suspension and non-magnetic gangue.

[0050] The aluminosilicate gangue particles did not undergo magnetic agglomeration; they remained in a monomeric dispersion state within the range of 5 to 20 micrometers. The effective mass of the aluminosilicate gangue particles... Minimal. Under the same centrifugal force field of 60G to 120G, the radial centrifugal force borne by the aluminosilicate gangue particles is calculated using the radial centrifugal force formula. Weak. A very weak radial centrifugal force. This causes the radial settling velocity of aluminosilicate gangue particles to approach zero. The local shear rate induced by aluminosilicate gangue particles in a non-Newtonian fluid. Below The low shear rate threshold is reached. Due to the extremely low local shear rate, the three-dimensional network structure of non-Newtonian fluids surrounding the aluminosilicate gangue particles remains intact, and the non-Newtonian fluids maintain their initial high apparent viscosity. This high apparent viscosity generates fluid drag, which interacts with a weak radial centrifugal force. A mechanical equilibrium is formed, stably suspending the aluminosilicate gangue particles within the fluid. Simultaneously, the high apparent viscosity of the non-Newtonian fluid effectively absorbs and suppresses macroscopic fluid turbulence caused by the high-speed operation of the sorting process, preventing the magnetic micro-agglomerates entering the heavy product enrichment zone from being re-entrained and mixed by the turbulent water flow. The stably suspended aluminosilicate gangue particles move axially with the non-Newtonian fluid and are discharged from the light product overflow port of the centrifugal sorting zone, achieving spatial stratification and isolation between vanadium-iron minerals and aluminosilicate gangue particles. For the continuous discharge control of the enriched material within the heavy product enrichment zone, those skilled in the art can set the discharge cycle interval parameter based on the slurry feed flow rate and heavy product yield. The setting of the discharge cycle interval parameter is a well-known technique in the field and will not be elaborated upon here.

[0051] Within the centrifugal separation zone, the material is separated into a heavy product underflow carrying magnetic micro-agglomerates and a light product overflow containing suspended aluminosilicate gangue particles. The physicochemical evolution process of product separation and rheological medium circulation is further subdivided into the following specific steps: S401: Physical dehydration of heavy product underflow and concentrate collection.

[0052] The heavy product underflow carrying magnetic micro-agglomerates is continuously drawn out of the centrifugal separation area. The heavy product underflow then enters the solid-liquid separation process to undergo mechanical extrusion. The mechanical extrusion pressure applied in the solid-liquid separation process is controlled within the range of 0.5 MPa to 1.5 MPa. The mechanical extrusion pressure forces the free water and residual non-Newtonian fluid inside the heavy product underflow to pass through the filter medium and be discharged. After mechanical extrusion to remove water, the magnetic micro-agglomerates are transformed into a filter cake with a moisture content of less than 15%. The filter cake is the final gravity concentrate enriched with vanadium and iron. The discharged free water and residual non-Newtonian fluid flow into the subsequent settling process. For controlling the rate of water filtration in the solid-liquid separation process, those skilled in the art can match the pressure gradient of the mechanical extrusion based on the equivalent diameter distribution characteristics of the magnetic micro-agglomerates. Pressure gradient control is a well-known technique in the art and will not be elaborated upon here.

[0053] S402: Low-shear rheological network reconstruction for gangue overflow.

[0054] The light product overflow containing suspended aluminosilicate gangue particles is discharged into the static settling zone. Upon entering the static settling zone, the light product overflow is removed from the high-speed rotational dynamic field of the centrifugal sorting zone, and the local shear rate within the light product overflow rapidly decreases and remains below [a certain value]. The low shear rate level was maintained. The light product overflow was allowed to settle and relax within the static settling zone for 5 to 15 minutes. Within this low shear rate level and relaxation time window, the polymeric segments of the macromolecular rheology modifier eliminated directional shear stress, and the polymeric segments spontaneously intertwined and entangled again under the drive of thermal motion within the aqueous solution. The three-dimensional spatial network structure disrupted by the high shear rate underwent physical reconstruction, and the apparent viscosity of the non-Newtonian fluid returned to its high value from the initial formulation stage.

[0055] S403: Double-layer compression and gangue flocculation sedimentation.

[0056] To overcome the suspension resistance caused by the high apparent viscosity, polyaluminum chloride (PAC) was quantitatively added as an inorganic coagulant into the static settling zone. The dosage of PAC was controlled within the range of 10 g / t to 30 g / t. Aluminosilicate gangue particles exhibit a negative surface potential in aqueous solution. During hydrolysis, PAC releases a large number of high-valence cations. These high-valence cations adsorb onto the surface of the aluminosilicate gangue particles, compressing the diffuse double layer thickness around them. The total interaction potential between adjacent aluminosilicate gangue particles... Following the DLVO colloidal stability theory, the total interaction potential energy Expressed by the following formula: in: This represents the total interaction potential energy between adjacent aluminosilicate gangue particles. This represents the electrostatic repulsion potential between adjacent aluminosilicate gangue particles. This represents the van der Waals attraction potential between adjacent aluminosilicate gangue particles.

[0057] The compression of the diffused electric double layer thickness leads to electrostatic repulsion potential energy. Significant attenuation. Controlled addition of polyaluminum chloride reduced the zeta potential on the surface of aluminosilicate gangue particles to the range of -5mV to +5mV. Electrostatic repulsion potential. The descent cannot resist the van der Waals attraction potential. Total interaction potential energy It exhibits a negative attraction state. Aluminosilicate gangue particles collide with each other and aggregate into dense, large flocs. These large flocs acquire sufficient gravitational settling momentum to overcome the resistance of the high apparent viscosity of the non-Newtonian fluid. After a settling period of 30 to 120 minutes, the large flocs settle to the bottom of the static settling zone and are discharged as final tailings.

[0058] S404: Supernatant recycling and rheology agent replenishment scheduling.

[0059] After the large-sized flocs settle, a clear supernatant precipitates in the upper layer of the static settling zone. This supernatant contains dissolved, undamaged anionic polyacrylamide macromolecular rheology modifier. The supernatant is pumped back to the fluid medium preparation step (S200) mentioned above, serving as the base solvent for preparing the non-Newtonian fluid. In the fluid medium preparation step, the residual mass concentration of anionic polyacrylamide in the returned supernatant is determined using an online capillary viscometer combined with a rheological standard curve. Based on a target mass concentration limit of 0.05% to 0.2%, fresh anionic polyacrylamide powder and water are quantitatively added to the returned supernatant, achieving a physical closed-loop recycling of the non-Newtonian fluid sorting medium. This physical closed-loop recycling avoids the significant external discharge and consumption of the macromolecular rheology modifier.

[0060] Comparative Example 1: Compared with the previous example, the difference is that the microwave selective fracturing and induced magnetic phase transition pretreatment process is cancelled, and the vanadium-containing tailings of the raw ore are directly crushed and dissociated by conventional mechanical ball milling. In addition, no weak reducing gas is introduced during the process. All other aspects are the same.

[0061] Comparative Example 2: The difference from the previous example is that the step of adding macromolecular rheology modifier is omitted, and conventional industrial water is used directly as the centrifugal separation medium; all other aspects are the same.

[0062] Comparative Example 3: The difference from the embodiment is that in the centrifugal sorting process, the magnetic field generating array is turned off, and no weak constant background magnetic field is applied inside the sorting area; all other aspects are the same.

[0063] Test Example 1 Gravity separation tests were conducted on the examples and comparative examples. The prepared slurries from the examples and comparative examples were pumped into a horizontal continuous discharge centrifuge equipped with an external constant magnetic field array. The operating angular velocity of the horizontal continuous discharge centrifuge was set to 55 rad / s, and the radial background magnetic field strength inside the separation chamber was fixed at 0.10 T. After continuous feeding for 30 minutes and stabilization of the flow field, the underflow slurry from the heavy product underflow outlet and the overflow slurry from the light product overflow outlet of the horizontal continuous discharge centrifuge were simultaneously collected. The collection time lasted for 5 minutes. The collected underflow slurry and overflow slurry were placed in a vacuum filter for solid-liquid separation and dehydration. The dehydrated solid materials were placed in a constant temperature drying oven and dried to constant weight at 105℃. The mass of the dried solid materials was weighed, and the concentrate yield of each group was calculated. After sampling and grinding, the total iron content and vanadium pentoxide content in the solid material were determined using inductively coupled plasma atomic emission spectrometry (ICP-AES). The total iron recovery rate and vanadium pentoxide recovery rate were calculated based on the feed grade and concentrate yield.

[0064] Table 1. Test results of gravity separation concentrate indicators in the examples and comparative examples. Test conclusions and mechanism analysis: The example showed the highest values ​​in concentrate grade and recovery rate. Comparative Example 1, using mechanical grinding without microwave-induced treatment, had a total iron recovery rate of 49.33%, lower than the 74.51% of the example, and a lower vanadium pentoxide grade. The mechanical grinding force mode resulted in the failure of the vanadium-bearing iron ore phase and the aluminosilicate gangue phase to dissociate along grain boundaries, producing fine-grained slime. No microwave-induced localized solid-state reduction reaction occurred, and the vanadium-bearing iron particles remained in a hematite state. During the centrifugal separation process, the vanadium-bearing iron particles did not undergo magnetic agglomeration, and the fine-grained vanadium-bearing iron minerals were discharged with the light product overflow. The comparative results indicate that microwave thermal stress cracking controls the dissociation particle size, and microwave-induced phase transformation increases the specific magnetization coefficient.

[0065] Comparative Example 2 used industrial water as the separation medium, achieving a concentrate yield of 23.64% and a total iron grade of 35.19%. The water-based medium lacks yield stress and viscosity support; the rotation of the horizontal continuous discharge centrifuge induces fluid turbulence, causing aluminosilicate gangue particles to enter the heavy product enrichment zone, resulting in the inclusion of aluminosilicate gangue particles in the gravity concentrate. In the example, a macromolecular rheology modifier was added to construct a spatial network structure, maintaining apparent viscosity. This suspended aluminosilicate gangue particles, which were then discharged with the light product overflow, improving the grade of the underflow concentrate.

[0066] In Comparative Example 3, no weak constant background magnetic field was applied in the sorting area, and the total iron recovery rate was 38.64%. Without the background magnetic field, the vanadium-containing iron particles were in a monomeric dispersion state. The monomeric vanadium-containing iron particles had small masses and low settling velocities in the centrifugal field, and the solid-liquid boundary layer did not generate shear rates that disrupted the non-Newtonian fluid network structure. The apparent viscosity of the non-Newtonian fluid did not decrease, and the vanadium-containing iron particles were discharged with the light products. In the Example 1, applying a background magnetic field caused the vanadium-containing iron particles to aggregate into magnetic micro-agglomerates. The settling momentum of the magnetic micro-agglomerates increased, the local shear rate increased, and the apparent viscosity of the fluid decreased, leading to the separation of the vanadium-containing iron minerals from the aluminosilicate gangue particles.

[0067] Based on comprehensive test data, microwave-induced magnetic phase transition enables vanadium-iron particles to aggregate, a weak constant magnetic field promotes mass amplification of these particles, and shear-thinning non-Newtonian fluid reduces local apparent viscosity and suspends aluminosilicate gangue particles. These combined technical features facilitate the separation of vanadium-containing tailings.

[0068] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A comprehensive gravity separation process for recovering residual vanadium and iron from vanadium-bearing tailings, characterized in that, Includes the following steps: S100: Microwave Selective Fracturing and Induced Magnetic Phase Transition; Vanadium-bearing tailings from the raw ore are continuously fed into a microwave reaction cavity, and pulsed microwave irradiation is applied under the protection of a weak reducing gas atmosphere. The difference in dielectric loss parameters between the vanadium-bearing iron ore phase and the aluminosilicate gangue phase is used to induce a thermal stress gradient at the interface between the vanadium-bearing iron ore phase and the aluminosilicate gangue phase. The thermal stress gradient induces microcracks to achieve selective fracturing and separation of the vanadium-bearing tailings from the raw ore. Combined with the microwave hot spot effect, a solid-phase reduction reaction is induced on the surface of the vanadium-bearing iron ore phase, which promotes the lattice reconstruction phase transition of hematite to magnetite, and the pre-treated material is obtained. S200: Preparation of shear-thinning non-Newtonian fluid medium; a non-Newtonian fluid with pseudoplastic rheological characteristics is prepared by adding a macromolecular rheology modifier into a solvent water. S300: Weak magnetic field coupling enhanced centrifugal separation; pretreated materials are mixed with non-Newtonian fluid to prepare a slurry, which is continuously pumped into the separation chamber of the centrifugal separator. Under the action of a weak constant background magnetic field, vanadium-iron particles enhanced by lattice reconstruction phase transformation overcome electrostatic repulsion and agglomerate to form large-mass magnetic micro-agglomerates. Under the centrifugal force field generated by the high-speed rotation of the centrifugal separator, the magnetic micro-agglomerates acquire centrifugal sedimentation momentum. When the magnetic micro-agglomerates penetrate the non-Newtonian fluid, a local high shear rate is induced in the solid-liquid boundary layer of the magnetic micro-agglomerates. The apparent viscosity of the non-Newtonian fluid in the local area of ​​the solid-liquid boundary layer decreases. The magnetic micro-agglomerates penetrate the non-Newtonian fluid layer and enter the heavy product enrichment zone. The non-magnetic fine-grained gangue remains in a monomeric dispersion state and is stably lifted by the non-Newtonian fluid and discharged with the overflow. S400: Product collection and closed-loop media circulation; The underflow concentrate is collected from the centrifugal separation equipment, and water is removed to obtain a gravity concentrate enriched with vanadium and iron. The light products discharged with the overflow enter the thickening settling tank and recombine under static hydrodynamic conditions to restore the high apparent viscosity state of non-Newtonian fluid. Inorganic coagulant is added into the thickening settling tank to promote flocculation and sedimentation of fine gangue as the final tailings. The supernatant overflowing from the top of the thickening settling tank is returned to the S200 step for closed-loop recycling.

2. The gravity separation process for recovering residual vanadium and iron from vanadium-bearing tailings according to claim 1, characterized in that, In step S100, the vanadium-bearing tailings of the raw ore are laid into a smooth material bed with a thickness of 20 mm to 50 mm. The smooth material bed is subjected to constant-speed microwave transmission at a running speed of 0.5 m / min to 2.0 m / min. The smooth material bed receives pulsed microwave irradiation with a frequency of 2.45 GHz and a power density of 10 kW / t to 50 kW / t. The pulsed microwave irradiation time is controlled between 15 seconds and 60 seconds. The vanadium-bearing iron ore phase is heated to 400℃ to 600℃. After the pretreated material is cooled to a temperature range of 80℃ to 120℃, it is discharged from the microwave reaction chamber.

3. The gravity separation process for recovering residual vanadium and iron from vanadium-bearing tailings according to claim 2, characterized in that, The process of microcracks induced by thermal stress gradient includes: a temperature gradient is constructed based on the volumetric heat source of pulsed microwave energy conversion within the vanadium-bearing iron ore phase; the temperature gradient causes the vanadium-bearing iron ore phase to exhibit a tendency for volume expansion and generates tensile-compressive combined thermal stress at the interface between the vanadium-bearing iron ore phase and the aluminosilicate gangue phase; the tensile-compressive combined thermal stress concentrates at the tip of the initial micro-defect and induces instability and propagation at the tip of the micro-defect to form microcracks when the stress intensity factor reaches and exceeds the critical value of fracture toughness; the stress intensity factor is jointly determined by the defect shape factor, local thermal stress, and the characteristic size of the micro-defect.

4. The gravity separation process for recovering residual vanadium and iron from vanadium-bearing tailings according to claim 1, characterized in that, In step S100, a weak reducing gas with a carbon monoxide volume fraction of 2% to 5% is introduced. The flow direction of the weak reducing gas is in countercurrent contact with the moving direction of the leveling material bed. The environment of the leveling material bed is maintained at a slightly positive pressure of 50 Pa to 200 Pa. The apparent contact residence time of the weak reducing gas inside the leveling material bed is 10 to 30 seconds, which promotes the lattice reconstruction phase transition of the hematite phase on the surface of the vanadium-bearing iron ore phase to the magnetite phase and increases the overall specific magnetization coefficient of the vanadium-bearing iron ore phase.

5. The gravity separation process for recovering residual vanadium and iron from vanadium-bearing tailings according to claim 4, characterized in that, During the lattice reconstruction phase transition, the partial pressure ratio of carbon dioxide to carbon monoxide in the reaction system is maintained within the range of 1.5 to 3.5 by controlling the volume fraction of carbon monoxide to keep the partial pressure ratio of carbon dioxide in the reaction system within the range of 1.5 to 3.

5. This controls the change in Gibbs free energy corresponding to the chemical thermodynamic driving force of the gas-solid phase interface reduction reaction to be negative, thus driving the gas-solid phase interface reduction reaction to remain in the magnetite phase formation stage.

6. The gravity separation process for recovering residual vanadium and iron from vanadium-bearing tailings according to claim 1, characterized in that, In step S200, the macromolecular rheology modifier is anionic polyacrylamide, with a mass concentration of 0.05% to 0.2%. The non-Newtonian fluid follows a power-law fluid model, and its flow characteristic index is distributed in the range of 0.4 to 0.

6. The apparent viscosity of the non-Newtonian fluid is determined by the shear stress and the shear rate it withstands, derived from the consistency coefficient. The apparent viscosity of the non-Newtonian fluid and the shear rate it withstands exhibit a negative exponential correlation.

7. The gravity separation process for recovering residual vanadium and iron from vanadium-bearing tailings according to claim 1, characterized in that, In step S300, the mass concentration of the slurry is 15% to 30%, the magnetic field strength of the weak constant background magnetic field is distributed in the range of 0.05T to 0.15T, and the radial magnetic field gradient inside the sorting cavity is controlled to approach zero. After the slurry enters the uniform weak constant background magnetic field, the magnetic dipole attraction generated by the vanadium-iron particles after the lattice reconstruction phase transition increases sharply and exceeds the electrostatic repulsion of the double electric layer, breaking the colloidal thermodynamic stability of the slurry system and causing the vanadium-iron particles to spontaneously agglomerate and form magnetic micro-agglomerates.

8. The gravity separation process for recovering residual vanadium and iron from vanadium-bearing tailings according to claim 7, characterized in that, Magnetic micro-aggregates acquire radial settling velocities under centrifugal force fields of 60G to 120G generated by centrifugal sorting equipment. The magnetic micro-aggregates penetrate the non-Newtonian fluid medium with radial settling velocities and induce local high shear rates at the solid-liquid boundary layer of the magnetic micro-aggregates. The decrease in apparent viscosity of the non-Newtonian fluid leads to a synchronous decrease in the fluid resistance exerted by the non-Newtonian fluid on the magnetic micro-aggregates, thus constructing a positive feedback dynamic mechanism of local shear force self-amplification and continuous decrease in apparent viscosity. The radial centrifugal force on the aluminosilicate gangue particles is weak, and the local shear rate induced by the aluminosilicate gangue particles remains under low shear rate conditions. The non-Newtonian fluid maintains the initial high apparent viscosity and generates fluid drag to stably suspend the aluminosilicate gangue particles.

9. The gravity separation process for recovering residual vanadium and iron from vanadium-bearing tailings according to claim 1, characterized in that, In step S400, the heavy product underflow is drawn out of the centrifugal separation area and enters the solid-liquid separation process to undergo mechanical compression. The magnetic micro-agglomerates are transformed into filter cake with a moisture content of less than 15% as the final gravity concentrate. The light product discharged with the overflow is discharged into the thickening settling tank and the directional shear stress is eliminated within the static relaxation time window to complete the physical reconstruction of the three-dimensional spatial network structure and restore the high apparent viscosity state. Polyaluminum chloride inorganic coagulant is quantitatively added into the thickening settling tank to compress the diffusion double layer thickness around the aluminosilicate gangue particles. This reduces the electrostatic repulsion potential energy between adjacent aluminosilicate gangue particles and makes them unable to resist the van der Waals attraction potential energy. The total interaction potential energy is in a negative attraction state, which causes the aluminosilicate gangue particles to aggregate into large-sized flocs and complete the settling.

10. The gravity separation process for recovering residual vanadium and iron from vanadium-bearing tailings according to claim 9, characterized in that, After the large-sized flocs settle, a clear supernatant is precipitated on the upper layer of the thickening tank. The supernatant is pumped back to the fluid medium preparation process as a base solvent. In the fluid medium preparation process, the residual mass concentration of macromolecular rheology modifier in the reflux supernatant is determined by an online capillary viscometer combined with a rheological standard curve, and the missing macromolecular rheology modifier dry powder is quantitatively replenished.

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