A method for the flotation of fine-grained intergrown siderite

Abstract

The present application relates to the technical field of mineral processing, and provides a flotation method of micro-fine particle intergrowth siderite, which comprises the following steps: grading and grinding of raw ore and particle size grading, so as to obtain coarse particle grade ore slurry, fine particle grade ore slurry and ultra-fine particle grade ore slurry; surface modification treatment is respectively performed on the coarse particle grade ore slurry, the fine particle grade ore slurry and the ultra-fine particle grade ore slurry, the modified ore slurries obtained are mixed, and then positive flotation, reverse flotation and concentrate post-treatment are performed, so as to obtain high-grade siderite concentrate; the method can greatly improve the TFe grade of iron concentrate and the comprehensive recovery rate of iron, and simultaneously realizes the reduction of reagent amount and the zero organic discharge of waste water.

Description

Technical Field

[0001] This invention relates to the field of mineral processing technology, and more specifically, to a flotation method for fine-grained symbiotic siderite. Background Technology

[0002] The low-grade, multi-element symbiotic siderite in the Panxi region is characterized by its fine-grained distribution, with iron minerals tightly bound to quartz, dolomite, and hematite, exhibiting severe heterogeneous agglomeration of mineral particles. Conventional flotation processes for this type of ore commonly encounter industry challenges, including loss of ultrafine iron particles, low iron concentrate grade and overall recovery rate, high consumption of organic reagents, and strong interference from calcium and magnesium impurities on the flocculation system.

[0003] For example, patent CN107952593A discloses a selective flocculation flotation method for fine-grained siderite. This method uses only citric acid as a dispersant and ordinary α-starch as a flocculant, and simultaneously separates coarse and fine mixed slurries. However, citric acid alone has a weak selective adsorption capacity for quartz gangue and cannot completely break up the heterogeneous agglomeration of siderite and quartz. In the environment where calcium and magnesium impurities coexist, the flocculation selectivity is poor, the iron concentrate grade is increased by less than 10%, the loss of iron metal in ultrafine particles is large, and there is a clear upper limit to the separation index.

[0004] Moreover, existing publicly available technologies mainly focus on reagent optimization to improve the flotation effect of siderite, but they generally still have defects such as low iron recovery rate of ultrafine particles, high flocculant dosage, significant interference of calcium and magnesium ions, and organic reagent residues in wastewater, making it difficult to achieve low-cost, high-recovery, and green industrial upgrading of high-calcium and magnesium micro-symbiotic siderite in the Panzhihua-Xichang region.

[0005] The surface process adjustments, such as the indiscriminate addition of magnetic seeds and localized improvements to flotation equipment, have not been based on the differences in adsorption kinetics of minerals of different particle sizes to construct a complete set of treatment processes. As a result, there are common defects such as low recovery rate of ultrafine iron, high dosage of organic flocculants, significant interference from calcium and magnesium ions, large consumption of magnetic seeds, and residual organic reagents in wastewater. It is difficult to achieve low-cost, high-recovery, and green industrial upgrading of high-calcium and magnesium micro-symbiotic siderite in the Panzhihua-Xichang region. Summary of the Invention

[0006] The purpose of this invention is to provide a flotation method for fine-grained symbiotic siderite, which can significantly improve the TFe grade of iron concentrate and the overall iron recovery rate, while simultaneously achieving reagent reduction and zero organic wastewater discharge.

[0007] The embodiments of the present invention are achieved through the following technical solutions: A flotation method for fine-grained symbiotic siderite includes the following steps: S1 Classification Grinding and Particle Size Classification After crushing the low-grade symbiotic siderite, the slurry was classified by ball milling and hydrocyclone multiple times to obtain coarse-grained slurry, fine-grained slurry and ultrafine-grained slurry respectively. S2 fractional in-situ differentiated surface modification (S21) Modification of coarse-grained slurry: After adjusting the pH of the coarse-grained slurry, sodium silicate is added, and after reacting for a period of time, modified coarse-grained slurry is obtained. (S22) Fine-grained mineral slurry modification: After adjusting the pH of the fine-grained mineral slurry, sodium silicate and citric acid are added, and after reacting for a period of time, modified fine-grained mineral slurry is obtained. (S23) Modification of ultrafine mineral slurry: After adjusting the pH of ultrafine mineral slurry, magnetic seeds are added and reacted for a period of time, then modified cationic flocculant is added and reacted for a period of time to obtain modified ultrafine mineral slurry; S3 forward and reverse flotation Modified coarse-grained slurry, modified fine-grained slurry, and modified ultrafine-grained slurry are mixed to obtain a mixed slurry. After adjusting the pH of the mixed slurry, sodium oleate is added, and aeration flotation is performed to obtain primary iron concentrate and positive flotation tailings. After the tailings from the direct flotation are concentrated and the pH of the slurry is adjusted, reverse flotation reagents are added to carry out two-stage reverse flotation to obtain reverse flotation tailings and iron concentrate. S4 Concentrate Post-processing After the iron concentrate is concentrated, dehydrated and dried, a high-grade siderite concentrate is obtained.

[0008] The technical solutions of the embodiments of the present invention have at least the following advantages and beneficial effects: This invention, based on in-situ interface control of mineral particle size differentiation and magnetic-chemical synergistic flocculation, constructs an integrated flotation method for siderite, encompassing hydraulic classification and differentiated modification, selective magnetic seed flocculation of ultrafine particles, and closed-loop regeneration of magnetic seeds. This differs from existing techniques that use uniform reagents across all particle sizes and indiscriminately add magnetic seeds throughout the process. By classifying the raw ore into different particle sizes, different particle sizes of the slurry are modified separately, eliminating the inherent contradiction between over-flocculation of coarse particles and escape of ultrafine particles. Only during the modification of the ultrafine particle slurry is a trace amount of ultrafine magnetic seeds selectively added. Magnetic attraction assists polymer bridging, achieving efficient mineral agglomeration with low reagent levels and effectively resisting interference from calcium and magnesium ions. The residual magnetic seeds are directly used as flocculants in wastewater, achieving dual use and closed-loop recycling of the magnetic seeds. This significantly improves the TFe grade of the final siderite concentrate and the overall iron recovery rate, while significantly reducing iron loss from tailings. Detailed Implementation

[0009] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0010] The following is a detailed description of a flotation method for fine-grained symbiotic siderite provided by an embodiment of the present invention.

[0011] A flotation method for fine-grained symbiotic siderite includes the following steps: S1 Classification Grinding and Particle Size Classification Low-grade symbiotic siderite is crushed to a particle size ≤2mm and fed into a ball mill for coarse grinding. The coarse grinding product is classified by a primary hydrocyclone. The coarse particles and sediment are returned to the ball mill for re-grinding, and the overflow is sent to a secondary stirred mill to complete the full dissociation of fine minerals. The dissociated slurry is sent to a secondary hydrocyclone for classification, which divides it into three independent slurry branches: coarse slurry (-0.074~+0.038mm), fine slurry (-0.038~+0.010mm), and ultrafine slurry (≤-0.010mm). The yield control range for each particle size is: coarse slurry 20%~30%, fine slurry 40%~50%, and ultrafine slurry 15%~25%.

[0012] The proportion of natural particles of -0.010mm in the raw ore is only 12%. After two-stage grinding and separation classification, the yield of ultrafine ore pulp is increased to the target range.

[0013] After grading, the separation processes of each particle size are independent and do not interfere with each other. When the particle size or impurity content of the raw ore fluctuates, the conditions of the modifying agent of a single branch can be adjusted separately. The entire separation system has excellent anti-disturbance performance. The three graded slurries are respectively transported to independent slurry conditioning and modification tanks for standby.

[0014] S2 fractional in-situ differentiated surface modification (1) Modification of coarse-grained slurry: Adjust the pH of the coarse-grained slurry to 5.0~5.5, add 100~200g / t of sodium silicate based on the mass of the coarse-grained slurry, stir for 5~8min to obtain modified coarse-grained slurry; sodium silicate selectively adsorbs onto the quartz surface to form a hydrophilic film, increasing electrostatic repulsion, breaking only the slight heterogeneous agglomeration of coarse particles, without changing the hydrophobicity of siderite flotation.

[0015] (2) Modification of fine-grained slurry: Adjust the pH of the fine-grained slurry to 6.0~7.0, add 150~250g / t of sodium silicate and 50~100g / t of citric acid, stir for 8~12min to obtain modified fine-grained slurry; the compounded reagents synergistically neutralize the Ca in the slurry. 2+ Mg2 + This weakens the aggregation strength between medium-sized minerals.

[0016] (3) Modification of ultrafine slurry: Adjust the pH of ultrafine slurry to 6.5~7.5, add 5~12mg / L of ultrafine magnetite seed with a -0.005mm content ≥90%, stir for 5~8min. The ultrafine magnetic seed has a huge specific surface area and a large number of unsaturated iron sites are exposed, which significantly improves the lattice matching adsorption efficiency. The magnetic seed selectively and firmly adsorbs onto the siderite surface by means of the lattice matching effect, so that the siderite particles are magnetized and modified. The composite particles have the strong subferromagnetism of magnetite. Subsequently, under the action of an external magnetic field, magnetic dipole attraction can be generated, which provides magnetic driving force for selective agglomeration. Then add modified cationic flocculant at a dosage of 50~60g / t, stir for 5~10min to obtain modified ultrafine slurry. Among them, the modified cationic flocculant is a copolymer of acrylamide and methacryloyloxyethyltrimethylammonium chloride with a mass ratio of 1:1.2~1.7 and a molecular weight of 5 million to 10 million. It achieves the aggregation of fine minerals by relying on the bridging effect of polymer chains.

[0017] The surface of the siderite composite particles after magnetic seed loading has a large number of hydroxyl sites and negative potential sites; the quaternary ammonium cation groups on the cationic flocculant molecular chain are adsorbed onto the surface of the composite particles through electrostatic attraction; the long polymer chains are simultaneously adsorbed onto the surface of multiple adjacent siderite-magnetite composite particles, forming polymer bridges that connect the fine siderite particles to each other, forming dense flocs with larger size and better sedimentation / flotation behavior; at the same time, the amide groups of the acrylamide structural unit can form intermolecular hydrogen bonds with the hydroxyl groups (≡Fe-OH) on the mineral surface, further enhancing the adsorption strength of the flocculant on the surface of the siderite-magnetic seed composite; the hydrogen bonding introduced by acrylamide improves the flocs' resistance to stirring and slurry shearing, preventing the fine flocs from breaking down into ultrafine particles again; in this way, relying on the dual effects of long-range magnetic attraction and polymer bridging, a low-impurity uniform mineral agglomerate is formed, which greatly weakens the destructive effect of calcium and magnesium ions on the floc structure. Through the synergistic treatment of magnetic seeds and modified cationic flocculants, siderite forms large agglomerates with good floatability, making it easier for them to adhere to flotation bubbles and float, thereby improving the flotation rate and recovery rate of fine siderite particles. The ultrafine gangue mud is kept in a dispersed state, reducing the covering of fine mud and the entrainment of fine particles, thus solving the common pain points of low recovery rate and difficulty in achieving both high concentrate grade in the flotation of fine siderite particles.

[0018] S3 merging, forward and reverse flotation Modified coarse-grained slurry, modified fine-grained slurry, and modified ultrafine-grained slurry are mixed to obtain a mixed slurry. The pH of the mixed slurry is adjusted to 6.5~7.0, and 300~600g / t of sodium oleate is added. The slurry is then aerated and floated for 8~12 minutes to obtain froth products and bottom slurry. The froth products are the primary iron concentrate, and the bottom slurry is the positive flotation tailings. The tailings from the direct flotation are concentrated to 25-35% of the mass concentration of the mixed pulp, and the pH of the pulp is adjusted to 11-12. Then, 100-200 g / t of calcium chloride, 800-1200 g / t of starch, and 70-150 g / t of N-dodecyl-1,3-propanediamine (all based on the mass of the concentrated direct flotation tailings) are added sequentially. Then, two-stage reverse flotation is carried out, with each stage lasting 6-10 minutes. This removes calcium-magnesium-silica gangues such as dolomite, calcite, and residual quartz. After two-stage reverse flotation, reverse flotation tailings and iron concentrate are obtained.

[0019] S4 Concentrate Concentration, Filtration, and Low-Temperature Drying The iron concentrate is concentrated by a thickener, dehydrated by plate and frame filter press, and dried at low temperature (≤105℃) to obtain the finished high-grade siderite concentrate.

[0020] Furthermore, it also includes S5. Performing magnetic seed weak magnetic field-assisted wastewater sedimentation and magnetic seed closed-loop regeneration: After step S3, the reverse flotation tailings are sent to a settling tank with a built-in permanent magnet and subjected to a weak static magnetic field of 20-50 mT for 20-40 min of static settling. The residual ultrafine magnetic seeds in the reverse flotation tailings act as natural floc nuclei to induce the rapid formation of magnetic flocs. The suspended solids (SS) in the supernatant are ≤50 mg / L, and all of them are recycled in a closed loop for the entire grinding, classification, and slurry conditioning process. The underflow from the settling is sent to an 80-120 kA / m weak magnetic separator to separate and recover the magnetic seeds. The magnetic seed recovery rate is ≥85%, and it can be directly recycled for the ultrafine particle slurry modification process. For wastewater treatment, only a trace amount of polyaluminum chloride inorganic coagulant is added as needed. There is no need to add polyacrylamide organic flocculant throughout the process, and the magnetic seed separation and wastewater settling can be achieved in one process.

[0021] During the flotation of siderite, the inventors discovered significant differences in the surface adsorption kinetics of siderite of different particle sizes. In-situ interface control based on mineral particle size differentiation is a feasible approach. Further research into the structure of siderite revealed that, using traditional methods—specifically, flotation with uniform reagents across all particle sizes—coarse-grained siderite is prone to over-flocculation, while ultrafine-grained siderite is prone to escape. Based on this, this application creatively conceives of a technical concept that involves classifying siderite to match each particle size with a dedicated modified reagent, thereby eliminating the inherent contradiction between over-flocculation of coarse-grained siderite and escape of ultrafine-grained siderite. The specific technical solution of this invention has been further designed.

[0022] This invention relies on the differences in surface adsorption kinetics of siderite of different particle sizes and the magnetic-electrostatic synergistic flocculation mechanism. First, low-grade symbiotic siderite is crushed to three particle sizes for classification. Through classification, each particle size is matched with a specific modifying agent. Furthermore, a trace amount of magnetic seeds is selectively added only during the modification of ultrafine particle slurry. With the help of magnetic attraction to assist polymer bridging, high-efficiency agglomeration with low reagents is achieved, effectively resisting the interference of calcium and magnesium ions. Then, gradient forward and reverse flotation, magnetic reagent-free wastewater sedimentation, and magnetic seed closed-loop regeneration are carried out to solve the problem of ultrafine metal loss and simultaneously achieve multiple goals such as iron concentrate upgrading, organic reagent reduction, zero organic wastewater discharge, and stable production line operation.

[0023] Raw material description All embodiments, comparative examples, and experimental examples of this invention used the same batch of low-grade multi-element symbiotic siderite ore from the Panzhihua-Xichang region. The chemical composition (mass fraction) of the ore was as follows: TFe 30.2%, SiO2 36.7%, CaO 7.1%, MgO 4.3%, Al2O 35.2%, and loss on ignition 10.5%. Mineral phase composition: siderite 58%, hematite 7%, primary magnetite 3%, gangue minerals are mainly quartz, dolomite and calcite; the natural proportion of -0.010mm particles in the raw ore is 12%, and the yield of ultrafine particles is increased to 15%~25% after grinding and classification. Coarse and fine particles are mixed and heterogeneous agglomeration is serious. Ultrafine magnetite seed: 92% of particles are -0.005mm, with a purity of ≥93%; Testing standards: Iron grade and recovery rate were determined by a combination of XRF fluorescence spectroscopy and chemical titration; suspended solids (SS) in wastewater were determined by gravimetric method; magnetic seed recovery rate was calculated by weak magnetic separation and weighing method.

[0024] Example 1 A flotation method for fine-grained symbiotic siderite includes the following steps: 1. Two-stage classifying grinding and hydraulic three-stage particle size classification Take 5 kg of low-grade, multi-element symbiotic siderite ore from the Panzhihua-Xichang region. Crush the ore to a particle size ≤ 2 mm using a jaw crusher and a double-roll crusher. Feed it into a ball mill for coarse grinding. The grinding product enters a primary hydrocyclone for classification. Coarse particles and sediment are returned to the ball mill for re-grinding. The overflow is sent to a secondary stirred mill to complete the full dissociation of fine minerals. After dissociation, the slurry is sent to a secondary hydrocyclone for precise classification, dividing it into three independent slurry branches: coarse particle size (-0.074 + 0.038 mm) with a yield of 25%, fine particle size (-0.038 + 0.010 mm) with a yield of 45%, and ultrafine particle size (-0.010 mm) with a yield of 20%. The three slurries are respectively transported to three sets of independent slurry conditioning and modification tanks for later use.

[0025] 2. In-situ differentiated surface modification based on particle size After the three slurries enter their respective conditioning tanks, targeted modification treatments are carried out based on the differences in adsorption kinetics on the surfaces of minerals of different particle sizes: (1) Modification of coarse-grained slurry: Adjust the pH of coarse-grained slurry to 5.2, add 0.75g of sodium silicate, stir for 8min to obtain modified coarse-grained slurry; (2) Modification of fine-grained mineral slurry: Adjust the pH of fine-grained mineral slurry to 6.5, add 1g of sodium silicate and 0.4g of citric acid, stir for 10min to obtain modified fine-grained mineral slurry; (3) Modification of ultrafine particle slurry: Adjust the pH of ultrafine particle slurry to 7.0, first add 8 mg / L of ultrafine magnetite seed (based on dry ore mass), stir for 6 min, the proportion of seed particle size -0.005 mm is 92%, then add 0.12 g of acrylamide and 0.18 g of methacryloyloxyethyltrimethylammonium chloride copolymer, stir for 8 min, and obtain modified ultrafine particle slurry; 3. Divide and merge gradient batch forward and reverse flotation Modified coarse-grained slurry, modified fine-grained slurry, and modified ultrafine-grained slurry were mixed to obtain a mixed slurry. The pH of the mixed slurry was adjusted to 6.8, and 450 g / t of sodium oleate (based on the mass of the mixed slurry) was added. Aeration flotation was carried out for 10 min. The froth product was the primary iron concentrate, and the bottom of the tank was the direct flotation tailings. The direct flotation tailings were concentrated to a slurry mass concentration of 30%, and the pH was adjusted to 11.5. 150 g / t of calcium chloride, 1000 g / t of starch, and 100 g / t of N-dodecyl-1,3-propanediamine (based on the mass of the concentrated direct flotation tailings) were added sequentially for two-stage reverse flotation. The flotation time for each stage was 8 min. After two-stage reverse flotation, reverse flotation tailings and iron concentrate were obtained. 4. Magnetic seed weak magnetic field-assisted wastewater sedimentation and magnetic seed closed-loop regeneration All flotation tailings are fed into a settling tank with a built-in permanent magnet, where a weak static magnetic field of 30mT is applied and the mixture is allowed to settle for 30 minutes. The measured value of suspended solids (SS) in the supernatant is 38mg / L, and the entire supernatant can be reused in the crushing, grinding, classification, and slurry preparation processes. The underflow from the settling process is fed into a 100kA / m weak magnetic separator to recover magnetic seeds. The single-cycle recovery rate of magnetic seeds is 88%, and the seeds are returned to the ultrafine particle slurry modification process via a screw conveyor for reuse. The amount of magnetic seeds added in each cycle is 13% of the initial amount. 5. Concentration, pressure filtration, and low-temperature drying of concentrate. The iron concentrate is concentrated by a thickener, dehydrated by plate and frame filter press, and dried at a low temperature of 105℃ until the moisture content is ≤8%, thus obtaining the finished siderite concentrate.

[0026] The obtained siderite concentrate was tested, and the results are as follows: the TFe grade of the iron concentrate was 61.2%, and the overall iron recovery rate was 69.5%; the iron recovery rate of coarse-grained grade was 76.5%, the iron recovery rate of fine-grained grade was 72.1%, and the iron recovery rate of ultrafine-grained grade was 66.8%; the magnetic seed recycling recovery rate was 88%; the SS in the wastewater was stable at 38 mg / L, and 100% closed-loop recycling could be achieved. After 30 days of continuous operation, the concentrate grade fluctuation was ≤±0.4%, and the recovery rate fluctuation was ≤±0.6%; there was no settling phenomenon in the flotation cell, and no flocculent agglomeration occurred in the coarse-grained grade, indicating that the system was operating stably.

[0027] Example 2 The difference between this embodiment and Embodiment 1 is that: Only the surface modification treatment process for ultrafine particle slurry is adjusted, as follows: (3) Ultrafine particle slurry: Adjust the pH of the ultrafine particle slurry to 7.0, add 5 mg / L of magnetic seed first, stir for 6 min; then add 0.13 g of acrylamide and 0.19 g of methacryloyloxyethyltrimethylammonium chloride copolymer, stir for 8 min.

[0028] The siderite concentrate obtained in this embodiment was tested, and the results are as follows: when the magnetic seed dosage was reduced to 5 mg / L, the TFe grade of the iron concentrate was 58.6%, and the overall recovery rate was 66.5%, which were 2.6% and 3.0% lower than those in Example 1, respectively; the recovery rate of ultrafine iron was 61.2%, which was 5.6% lower than that in Example 1; the magnetic seed recycling recovery rate was 86%, and the amount of magnetic seed replenished in each cycle was 14% of the initial addition amount; the SS in the wastewater was stable at 37 mg / L; there was no settling phenomenon in the flotation cell, no flocculent agglomeration was observed in the coarse particles, and the system operated stably.

[0029] Example 3 The difference between this embodiment and Embodiment 1 is that: Only the surface modification treatment process for ultrafine particle slurry is adjusted, as follows: (3) Ultrafine particle slurry: Adjust the pH of the ultrafine particle slurry to 7.0, add 7 mg / L of magnetic seed first, stir for 6 min; then add 0.12 g of acrylamide and 0.18 g of methacryloyloxyethyltrimethylammonium chloride copolymer, stir for 8 min.

[0030] The siderite concentrate obtained in this embodiment was tested, and the results are as follows: when the magnetic seed dosage was 7 mg / L, the TFe grade of the iron concentrate was 60.1%, and the overall recovery rate was 68.2%, which were 1.1% and 1.3% lower than those in Example 1, respectively, but 1.5% and 1.7% higher than those in Example 2, respectively; the recovery rate of ultrafine iron was 63.5%, which was 3.3% lower than that in Example 1, but 2.3% higher than that in Example 2; the magnetic seed recycling recovery rate was 87%, and the SS in the wastewater was stable at 40 mg / L; there was no settling phenomenon in the flotation cell, no flocculent agglomeration occurred in the coarse particles, and the system operated stably.

[0031] Example 4 The difference between this embodiment and Embodiment 1 is that: Only the surface modification treatment process for ultrafine particle slurry is adjusted, as follows: (3) Ultrafine particle slurry: Adjust the pH of the ultrafine particle slurry to 7.0, add 10 mg / L of magnetic seed first, stir for 6 min; then add 0.12 g of acrylamide and 0.18 g of methacryloyloxyethyltrimethylammonium chloride copolymer, stir for 8 min.

[0032] The siderite concentrate obtained in this embodiment was tested, and the results are as follows: when the magnetic seed dosage was increased to 10 mg / L, the TFe grade of the iron concentrate was 63.5%, and the overall recovery rate was 70.8%, which were 2.3% and 1.3% higher than those in Example 1, respectively; the recovery rate of ultrafine iron was 68.1%, which was 1.3% higher than that in Example 1; the magnetic seed recycling recovery rate was 89%, and the SS in the wastewater was stable at 39 mg / L; there was no settling phenomenon in the flotation cell, no flocculent agglomeration was observed in the coarse particles, and the system operated stably.

[0033] Example 5 The difference between this embodiment and Embodiment 1 is that: Only the surface modification treatment process for ultrafine particle slurry is adjusted, as follows: (3) Ultrafine particle slurry: Adjust the pH of the ultrafine particle slurry to 7.0, add 11 mg / L of magnetic seed first, stir for 6 min; then add 0.12 g of acrylamide and 0.18 g of methacryloyloxyethyltrimethylammonium chloride copolymer, stir for 8 min.

[0034] The siderite concentrate obtained in this embodiment was tested, and the results are as follows: when the magnetic seed dosage was increased to 11 mg / L, the TFe grade of the iron concentrate was 63.9%, and the overall recovery rate was 71.1%, which were 0.4% and 0.3% higher than those in Example 4, respectively; the recovery rate of ultrafine iron was 68.5%, which was 0.4% higher than that in Example 4; the magnetic seed recycling recovery rate was 89%, and the SS in the wastewater was stable at 40 mg / L; there was no settling phenomenon in the flotation cell, no flocculent agglomeration was observed in the coarse particles, and the system operated stably.

[0035] The results of Examples 1-5 indicate that at a magnetic seed dosage of 5 mg / L, the surface of the ultrafine slurry may show increased iron loss due to insufficient magnetic seed coverage, weakened long-range magnetic attraction, and the inability of some particles to effectively participate in magnetic flocculation. At a magnetic seed dosage of 10 mg / L, the ultrafine slurry exhibits the best magnetic seed coverage, magnetic flocculation performance, iron concentrate grade, and ultrafine iron recovery rate. While there is still an overall gain when the magnetic seed dosage is increased to 11 mg / L, the gain is not significant. This demonstrates that 5 mg / L is the feasible lower limit for this process; below this value, the selective flocculation effect significantly decreases. Optimally, the magnetic seed addition range is 8-10 mg / L.

[0036] Example 6 The difference between this embodiment and Embodiment 1 is that: The raw ore is graded into different particle sizes, as detailed below: In step 1, the coarse particle size (-0.074 ± 0.045 mm) has a yield of approximately 22%, the fine particle size (-0.045 ± 0.015 mm) has a yield of approximately 43%, and the ultrafine particle size (-0.015 mm) has a yield of approximately 25%. The ultrafine particle size was increased from 0.010 mm to 0.015 mm, resulting in more medium-sized fine particles entering the ultrafine particle branch, and the ultrafine particle yield increased from 20% to 25%. The siderite concentrate obtained in this embodiment was tested, and the results are as follows: After adjusting the particle size boundary, the TFe grade of the iron concentrate was 58.8%, and the comprehensive recovery rate was 66.9%, which were 2.4% and 2.6% lower than those in Example 1, respectively; the iron recovery rate of the ultrafine particles was 63.5%, which was 3.3% lower than that in Example 1; the yield of ultrafine particles increased from 20% to 25%, and the absolute consumption of magnetic seeds increased, but the amount of raw ore added per unit remained unchanged at 8 mg / L.

[0037] Example 7 The difference between this embodiment and Embodiment 1 is that: This embodiment is an industrial scale-up verification test. A 72-hour continuous industrial test was conducted on an industrial flotation production line with a daily processing capacity of 500 t / d at a mineral processing plant in the Panzhihua-Xichang region. The aim was to verify the feasibility and reliability of transforming the process of this invention from laboratory scale to industrial production scale, and to examine the operational stability of the equipment and the consistency of the separation indicators under long-term continuous operation conditions. Details are as follows: The properties of the raw ore are basically consistent with the parameters of the basic test raw materials (TFe fluctuates between 29.5% and 31.0%), belonging to the typical high-calcium-magnesium fine-grained low-grade siderite ore of the Panxi region. The original main equipment of the production line is a two-stage ball mill plus a two-stage forward and reverse flotation system. This test only added a two-stage hydrocyclone classifier, a magnetic seed addition metering device, and modified the settling tank to include a permanent magnet. No large equipment such as a roasting furnace was added to verify the ease of modification of the invention on the basis of the existing industrial production line.

[0038] The specific steps are as follows: 1. Two-stage classifying grinding and hydraulic three-stage particle size classification The raw ore, crushed to -2mm, is coarsely ground in a ball mill and then enters a primary hydrocyclone for classification. Coarse particles and sediment are returned to the ball mill for regrinding, while the overflow is sent to a secondary stirred mill for enhanced dissociation of fine minerals. The ore discharged from the secondary stirred mill enters a newly added secondary hydrocyclone group, which is divided into three independent branches for different particle sizes: coarse particles (-0.074 + 0.038mm), fine particles (-0.038 + 0.010mm), and ultrafine particles (-0.010mm). The particle size yield control range is the same as in Example 1. The three slurries are sent to independent slurry preparation tanks for later use.

[0039] 2. In-situ differentiated surface modification based on particle size The three slurries were fed into separate mixing tanks for differentiated modification: (1) Coarse-grained slurry: Adjust the pH of the coarse-grained slurry to 5.2, add 150 g / t of sodium silicate based on the mass of the coarse-grained slurry, stir for 8 min to obtain modified coarse-grained slurry; (2) Fine-grained slurry: Adjust the pH of the fine-grained slurry to 6.5, add 210 g / t of sodium silicate and 80 g / t of citric acid based on the mass of the fine-grained slurry, stir for 10 min to obtain modified fine-grained slurry; (3) Ultrafine particle size slurry: Adjust the pH of the ultrafine particle size slurry to 7.0. Based on the mass of the ultrafine particle size slurry, first add 8 mg / L of ultrafine magnetite seed and stir for 6 min; then add 55 g / t of acrylamide and methacryloyloxyethyltrimethylammonium chloride copolymer with a mass ratio of 1:1.5 and stir for 8 min to obtain modified ultrafine particle size slurry; 3. Divide and merge gradient batch forward and reverse flotation Modified coarse-grained slurry, modified fine-grained slurry, and modified ultrafine-grained slurry were mixed to obtain a mixed slurry. The pH of the mixed slurry was adjusted to 6.8, and 450 g / t of sodium oleate (based on the mass of the mixed slurry) was added. The aeration flotation time was 10 min. The froth product of the direct flotation was the primary iron concentrate. The tailings at the bottom of the tank were concentrated to a slurry mass concentration of 30% by a thickener and then entered the reverse flotation system. The pH of the slurry was adjusted to 11.5, and 150 g / t of calcium chloride, 1000 g / t of starch, and 100 g / t of N-dodecyl-1,3-propanediamine (based on the mass of the concentrated direct flotation tailings) were added sequentially. Two-stage reverse flotation was carried out, with a single-stage flotation time of 8 min. After two-stage reverse flotation, reverse flotation tailings and iron concentrate were obtained. 4. Magnetic seed weak magnetic field-assisted wastewater sedimentation and magnetic seed closed-loop regeneration All flotation tailings are fed into a settling tank with a built-in permanent magnet and a magnetic field strength of 30mT. After settling for 30 minutes, the measured SS value of the supernatant is 39mg / L, which can be completely reused in upstream processes such as grinding, classification, and slurry preparation. The underflow from the settling passes through a weak magnetic separator (magnetic field strength 100kA / m) to recover magnetic seeds. The magnetic seeds are then returned to the ultrafine particle slurry modification process via a screw conveyor for recycling. 5. Concentration, pressure filtration, and low-temperature drying of concentrate. Iron concentrate is concentrated using an existing thickener, dehydrated using a plate and frame filter press, and dried at a low temperature of 105℃ to obtain finished siderite concentrate.

[0040] Industrial test results: The average TFe grade of iron concentrate was 61.1% after 72 hours of continuous operation, and the comprehensive iron recovery rate was 69.3%, which was 0.2% lower than that of Example 1, and the deviation from the laboratory index of Example 1 was ≤0.7%; the SS in the wastewater was stable at 39 mg / L, the magnetic seed recycling recovery rate was 87%, and there were no abnormal phenomena such as settling tank, blockage, or fine sludge runoff during operation, which verified the feasibility and long-term stability of the process of this invention at an industrial scale of 500 t / d.

[0041] Comparative Example 1 This comparative example uses 5 kg of low-grade siderite ore from the Panzhihua-Xichang region, identical to that in Example 1. No hydraulic classification is performed throughout the process, no ultrafine magnetic seeds are added, and dispersants and flocculants are added uniformly across all particle sizes. The specific steps include the following: 1. Grinding and pulp preparation The raw ore was crushed to a particle size ≤2mm and then ground through a ball mill and a stirred mill. The grinding fineness was controlled at the same overall grinding fineness level as in Example 1. However, unlike the three-stage hydraulic classification process in Example 1 of this invention, this comparative example does not undergo a two-stage hydrocyclone classification. After all the grinding products are mixed, a mixed slurry of all particle sizes is formed (approximately 90% -0.074mm and approximately 20% -0.010mm), with a mixture of coarse and fine particles and severe heterogeneous agglomeration. 2. Uniform surface modification across the entire particle size range Adjust the pH of the whole-particle-size mixed mineral slurry to 6.5. Based on the mass of the whole-particle-size mixed mineral slurry, add 200 g / t of sodium silicate and 80 g / t of citric acid as compound dispersants, and then add 60 g / t of modified cationic flocculant. The modified cationic flocculant includes a copolymer of acrylamide and methacryloyloxyethyltrimethylammonium chloride in a mass ratio of 1:1.5. Stir for 10 min to obtain a uniform modified mineral slurry. 3. Flotation process: consistent with Example 1. 4. Tailings wastewater treatment The tailings wastewater settling process uses traditional methods, directly adding 12g / t of standard-dosage polyacrylamide flocculant without any magnetic seed addition or recovery process. However, polyacrylamide is a non-selective flocculant, which, while flocculating the tailings, also flocculates unrecovered fine iron mineral particles, further exacerbating iron loss.

[0042] 5. Concentrate processing The concentrate is concentrated, filtered under pressure, and dried at 105℃ to obtain the iron concentrate product.

[0043] Under unified flotation conditions across all particle sizes, the TFe grade of the iron concentrate was 56.1%, and the overall recovery rate was 64.2%, representing decreases of 5.1% and 5.3% respectively compared to Example 1. The initial PAM dosage in the wastewater was 12 g / t, and a large amount of organic reagent residue was detected in the effluent, making long-term closed-loop reuse impossible. After 7 days of continuous operation, the recovery rate of ultrafine iron decreased from 58.3% to 47.6%, while the iron grade of the tailings (-0.010 mm) increased from 9.2% to 14.5%. The flotation cells exhibited significant foam stickiness, unstable foam layers, and a large amount of entrained fine mud. The PAM dosage increased from 12 g / t to 48 g / t, and the accumulation of organic reagents led to continuous deterioration of the reclaimed water quality, causing the system to become unstable. This indicates that the traditional whole-particle separation process, which does not classify the raw ore or add magnetic seeds, has significant defects and cannot meet the industrial separation requirements of high-calcium-magnesium fine-grained siderite in the Panzhihua-Xichang region.

[0044] Comparative Example 2 The difference between this comparative example and Example 1 is that no ultrafine magnetic seeds are added. This aims to verify the irreplaceable role of magnetic seeds in the selective flocculation of ultrafine particles, that is, to verify the technical advantages of "magnetic-chemical synergistic flocculation" over "single chemical flocculation." Specifically, The modification steps for ultrafine particle slurry are as follows: Adjust the pH of the ultrafine particle slurry to 7.0, then directly add 0.12g of acrylamide and 0.18g of methacryloyloxyethyltrimethylammonium chloride copolymer, stir for 8 minutes to obtain modified ultrafine particle slurry; Under non-magnetic conditions, there is a lack of selective recognition mechanism between ultrafine siderite and gangue minerals such as quartz. The polymer chains of cationic flocculants are indiscriminately adsorbed on the surface of all negatively charged mineral particles in the solution, forming non-selective heterogeneous flocculation, which makes it impossible to achieve selective separation of siderite and gangue.

[0045] Subsequent tailings settling still employed a 30mT weak static magnetic field for 30 minutes. However, due to the lack of magnetic seed addition, the slurry lacked magnetic floc nuclei, and the weak magnetic field could not induce the formation of magnetic flocs, resulting in a significant decrease in settling efficiency. The settling underflow was treated by a weak magnetic separator, but because no magnetic seed could be recovered, the magnetic seed recovery rate was 0%.

[0046] The obtained siderite concentrate was tested. The results showed that after removing the magnetic seed, the TFe grade of the iron concentrate was 57.8%, and the overall recovery rate was 65.1%, which were 3.4% and 4.4% lower than those in Example 1, respectively. The recovery rate of ultrafine iron was only 52.3%, which was 14.5% lower than that in Example 1. Even with a significant increase in the amount of organic flocculant, it was still impossible to compensate for the loss of selective agglomeration efficiency without the magnetic seed. After 30 minutes of settling, the SS in the supernatant reached 85 mg / L, far exceeding the reuse standard (≤50 mg / L). This indicates that without the assistance of the magnetic seed, the cationic flocculant exhibits non-selective adsorption, and a large amount of ultrafine iron minerals enter the tailings along with the gangue. Magnetic-chemical synergistic flocculation is irreplaceable in the selective recovery of ultrafine particles.

[0047] Comparative Example 3 The difference between this comparative example and Example 1 is that it does not include hydraulic classification, aiming to verify the necessity of differentiated modification based on particle size, that is, to verify the technical advantage of "selective addition of magnetic seeds by particle size" over "indiscriminate addition of magnetic seeds across the entire range". Specifically, 1. Grinding and whole-size blending modification (without classification) After the raw ore is crushed, it is ground through a ball mill and a stirred mill to achieve the same overall grinding fineness as in Example 1. However, unlike the three-stage hydraulic classification in Example 1, this comparative example does not undergo a two-stage hydrocyclone classification. All grinding products are mixed to form a full-size mixed slurry, in which coarse particles (-0.074 + 0.038 mm) and ultrafine particles (-0.010 mm) coexist in the same slurry system. After all the slurry was mixed, the pH was uniformly adjusted to 7.0. An ultrafine magnetic seed of 8 mg / L was added in one go, and the mixture was stirred for 6 minutes. Then, a modified cationic flocculant was added and stirred for another 8 minutes. Under this global addition mode, the magnetic seed could not selectively enrich the surface of ultrafine siderite particles, but rather adsorbed indiscriminately onto siderite particles of all sizes. After the coarse-grained siderite was marked with the magnetic seed, it attracted each other due to magnetic attraction during stirring and subsequent flotation, forming large magnetic agglomerates whose mass exceeded the bubble carrying capacity, resulting in settling tank losses.

[0048] The obtained siderite concentrate was tested. The results showed that after removing hydraulic classification, the TFe grade of the iron concentrate was 57.2%, and the overall recovery rate was 65.5%, which were 4.0% and 4.0% lower than those in Example 1, respectively. The iron recovery rate of coarse-grained grade decreased from 76.5% to 64.8%, a decrease of 11.7%, and the TFe grade of coarse-grained material in the settling tank was as high as 18.6%, indicating that the coarse-grained iron minerals were severely lost due to over-flocculation in the settling tank. The iron recovery rate of ultrafine-grained grade was 58.4%, which was 8.4% lower than that in Example 1. This was because some magnetic seeds were competitively adsorbed by coarse particles under the whole-area magnetic seed addition mode, resulting in insufficient adhesion of ultrafine particles. This indicates that after removing hydraulic classification, the magnetic seeds could not be matched according to particle size differences. This shows the importance of differentiated modification of raw ore by classification.

[0049] In summary, after weak magnetic field-assisted sedimentation, the flotation wastewater produced by the flotation methods in the various embodiments of this invention has a suspended solids (SS) concentration of ≤50 mg / L in the supernatant, meeting the requirements for mineral processing reclaimed water quality. Results from 10 consecutive rounds of closed-loop recycling tests show that the reclaimed water has no significant negative impact on flotation indicators; concentrate grade fluctuation is ≤±0.3%, iron recovery rate fluctuation is ≤±0.5%, and separation indicators show no significant deterioration. This demonstrates that the reclaimed water quality after magnetic sedimentation treatment is stable and can be recycled long-term.

[0050] The magnetic seed recovery rate remained stable at 85%~90% per cycle, with a magnetic seed loss rate of 11%~14% per cycle. The amount of magnetic seed replenished was 11%~14% of the initial amount. After 10 consecutive cycles, the magnetic seed maintained good activity, and the sorting index showed no downward trend, proving that the magnetic seed did not undergo significant surface oxidation or activity decay during the cycle.

[0051] The entire wastewater treatment system requires no continuous addition of polyacrylamide flocculant, a stark contrast to Comparative Example 1 where the artificial addition of polyacrylamide led to continuous deterioration of the reclaimed water quality. This system truly achieves zero discharge of mineral processing wastewater and eliminates the accumulation of organic reagents. The magnetic seed recycling system is stable and reliable, offering both environmental and economic benefits.

[0052] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A flotation method for fine-grained symbiotic siderite, characterized in that, Includes the following steps: S1 Classification Grinding and Particle Size Classification After crushing the low-grade symbiotic siderite, the slurry was classified by ball milling and hydrocyclone multiple times to obtain coarse-grained slurry, fine-grained slurry and ultrafine-grained slurry respectively. S2 fractional in-situ differentiated surface modification (S21) Modification of coarse-grained slurry: After adjusting the pH of the coarse-grained slurry, sodium silicate is added, and after reacting for a period of time, modified coarse-grained slurry is obtained. (S22) Fine-grained mineral slurry modification: After adjusting the pH of the fine-grained mineral slurry, sodium silicate and citric acid are added, and after reacting for a period of time, modified fine-grained mineral slurry is obtained. (S23) Modification of ultrafine mineral slurry: After adjusting the pH of ultrafine mineral slurry, magnetic seeds are added and reacted for a period of time, then modified cationic flocculant is added and reacted for a period of time to obtain modified ultrafine mineral slurry; S3 forward and reverse flotation Modified coarse-grained slurry, modified fine-grained slurry, and modified ultrafine-grained slurry are mixed to obtain a mixed slurry. After adjusting the pH of the mixed slurry, sodium oleate is added, and aeration flotation is performed to obtain primary iron concentrate and positive flotation tailings. After the tailings from the direct flotation are concentrated and the pH of the slurry is adjusted, reverse flotation reagents are added to carry out two-stage reverse flotation to obtain reverse flotation tailings and iron concentrate. S4 Concentrate Post-processing After the iron concentrate is concentrated, dehydrated and dried, a high-grade siderite concentrate is obtained.

2. The flotation method for fine-grained symbiotic siderite according to claim 1, characterized in that, It also includes S5. Magnetic seed regeneration: The reverse flotation tailings are sent into a permanent magnet settling tank, a weak static magnetic field of 20~50mT is applied for static settling, and the settling underflow is sent to a weak magnetic separator to separate and recover the magnetic seeds.

3. The flotation method for fine-grained symbiotic siderite according to claim 2, characterized in that, The recovered magnetic seeds are directly recycled in S23.

4. The flotation method for fine-grained symbiotic siderite according to claim 1, characterized in that, In S1, the particle size of the coarse-grained slurry is -0.074 to +0.038 mm, the particle size of the fine-grained slurry is -0.038 to +0.010 mm, and the particle size of the ultrafine-grained slurry is ≤ -0.010 mm.

5. The flotation method for fine-grained symbiotic siderite according to claim 1, characterized in that, In S2, the pH of the coarse-grained slurry is adjusted to 5.0~5.5; And / or, adjust the pH of the fine-grained slurry to 6.0–7.0; And / or, adjust the pH of the ultrafine slurry to 6.5~7.

5.

6. The flotation method for fine-grained symbiotic siderite according to claim 1, characterized in that, In S2, 100~200g / t of sodium silicate is added based on the mass of coarse-grained slurry; Add 150~250g / t of sodium silicate and 50~100g / t of citric acid based on the mass of fine-grained slurry; Based on the mass of ultrafine slurry, first add 5~12mg / L of magnetic seed, then add 50~60g / t of modified cationic flocculant.

7. The flotation method for fine-grained symbiotic siderite according to claim 1, characterized in that, In S2, the modified cationic flocculant is a copolymer of acrylamide and methacryloyloxyethyltrimethylammonium chloride in a mass ratio of 1:1.2~1.

7.

8. The flotation method for fine-grained symbiotic siderite according to claim 1, characterized in that, In S2, the proportion of magnetic seeds with a particle size of -0.005mm is ≥90%.

9. The flotation method for fine-grained symbiotic siderite according to claim 1, characterized in that, In S3, the reverse flotation reagents are calcium chloride, starch, and N-dodecyl-1,3-propanediamine. Based on the mass of the positive flotation tailings, the addition amounts of calcium chloride, starch, and N-dodecyl-1,3-propanediamine are 100~200g / t, 900~1100g / t, and 90~110g / t, respectively.

10. The flotation method for fine-grained symbiotic siderite according to claim 1, characterized in that, In S3, sodium oleate is added after the pH of the mixed slurry is adjusted to 6.5~7.

0. The amount of sodium oleate added is 300~600g / t based on the mass of the mixed slurry.