A staged magnetic separation process for a sulphur-containing magnetite

Abstract

This invention belongs to the field of mineral processing technology. Specifically, it discloses a graded magnetic separation process for sulfur-containing magnetite. By classifying the ore and dynamically adjusting the magnetic field strength according to the characteristics of different particle sizes, the orientation of iron and sulfur minerals is precisely controlled, achieving optimized adjustment of element orientation. This promotes efficient separation of sulfur and magnetite, improves the grade of iron concentrate, reduces sulfur content, and simultaneously reduces iron mineral loss, thereby increasing the resource utilization rate of both iron and sulfur. The process design of this invention is scientifically sound, with controllable operating costs, high resource utilization, and significant environmental benefits, providing a practical solution for the efficient and clean utilization of sulfur-containing magnetite.

Description

Technical Field

[0001] This invention belongs to the field of mineral processing technology and relates to a beneficiation method for iron ore, specifically a graded magnetic separation process for sulfur-containing magnetite. Background Technology

[0002] Sulfur-bearing magnetite is an important source of iron and sulfur minerals in my country. Its mineral composition is complex, with the main iron minerals including magnetite, pyrite, marcasite, and pyrrhotite. Traditional beneficiation processes typically use magnetic separation as a pretreatment step, separating waste rock after crushing and screening the ore into different particle sizes using a magnetic separator. However, in actual production, the complex interaction between ore particle size, magnetite content, sulfur mineral content, and magnetic field strength leads to two prominent problems during magnetic separation: first, some sulfur minerals remain in the iron concentrate, affecting its quality; second, some iron minerals are lost with the tailings, resulting in resource waste. This incomplete separation directly necessitates additional desulfurization and iron removal processes in subsequent steps, increasing production costs and reducing overall process efficiency.

[0003] Existing technologies for treating sulfur-bearing magnetite mainly include magnetic separation, flotation, and roasting. Among these, magnetic separation is widely used due to its simplicity and low cost. However, traditional magnetic separation processes often use a single magnetic field strength to process mixed-size ore, failing to fully consider the differences in the occurrence states of sulfur minerals and magnetite in different particle sizes. For example, in coarse-grained ore, sulfur minerals often exist in the form of inclusions or intergrowths, requiring a higher magnetic field strength for effective separation. In contrast, fine-grained ore has a higher degree of liberation of individual magnetite particles; if the magnetic field strength is too high, it can easily adsorb gangue minerals and sulfur minerals, thus reducing the concentrate grade. While flotation can effectively remove sulfur minerals, it has stringent requirements for pulp concentration and reagent formulation, and it easily generates a large amount of beneficiation wastewater, posing a significant environmental burden. Roasting converts sulfur minerals into sulfur dioxide gas through high-temperature oxidation, achieving sulfur-iron separation, but it consumes a lot of energy, requires large equipment investments, and can easily cause magnetite to oxidize into hematite during roasting, reducing iron recovery. Therefore, developing a graded magnetic separation process that can dynamically adjust the magnetic field strength according to the particle size and composition of the ore, based on the mineral characteristics of sulfur-containing magnetite, is of great significance for improving the quality of iron concentrate, reducing sulfur content, and reducing resource waste. Summary of the Invention

[0004] To address the problem of unsatisfactory sulfur-iron separation in traditional beneficiation processes for sulfur-containing magnetite, this invention proposes a graded magnetic separation process for sulfur-containing magnetite. By classifying the ore and dynamically adjusting the magnetic field strength according to the characteristics of different particle sizes, the orientation of iron and sulfur minerals is precisely controlled, achieving optimized adjustment of element orientation. This promotes efficient separation of sulfur minerals and magnetite, improves the grade of iron concentrate, reduces sulfur content, minimizes iron mineral loss, and simultaneously improves the resource utilization rate of both iron and sulfur.

[0005] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is specifically as follows:

[0006] A grading magnetic separation process for sulfur-containing magnetite, the grading magnetic separation process comprising:

[0007] 1) The sulfur-containing magnetite is crushed and screened to obtain coarse and fine ore particles.

[0008] 2) Perform characteristic analysis on coarse and fine ore particles respectively to obtain characteristic data of coarse and fine ore particles, including particle size, sulfur mineral content and magnetite content.

[0009] 3) Establish a mathematical model for the magnetic field strength of strong magnetic separation of coarse-grained ore (the magnetic field strength in this step is relatively high, so it is called strong magnetic separation for easy distinction). Using the characteristic data of coarse-grained ore as independent variables, the magnetic field strength of strong magnetic separation of coarse-grained ore is calculated through this mathematical model. After the strong magnetic separation is completed, strong magnetic concentrate and strong magnetic tailings are obtained.

[0010] 4) Establish a mathematical model for the magnetic field strength of weak magnetic separation of fine-particle minerals (the magnetic field strength in this step is relatively low, so it is called weak magnetic separation for easy distinction). Using the characteristic data of fine-particle minerals as independent variables, the magnetic field strength of weak magnetic separation of fine-particle minerals is calculated through this mathematical model. After the weak magnetic separation is completed, weak magnetic concentrate and weak magnetic tailings are obtained.

[0011] Preferably, in step 1), the particle size range of the coarse-grained mineral material is 3~30mm (i.e., greater than 3mm and less than or equal to 30mm). The particle size range of the fine-grained mineral material is ≤3mm.

[0012] Preferably, in step 3), the mathematical model for the magnetic field strength of the coarse-grained ore in strong magnetic separation is:

[0013] (I).

[0014] In the formula: H1 is the magnetic field strength during strong magnetic separation, in GS. K1 is the magnetic field strength adjustment coefficient during strong magnetic separation, with a value of 3000~4000. S1 is the mass content of sulfur minerals in coarse-grained ore, %. M1 is the mass content of magnetite in coarse-grained ore, %. r1 is the magnetite content adjustment coefficient, with a value of 0.01~0.5. D1 is the average particle size of coarse-grained ore, in mm. b1 is the average particle size adjustment index during the strong magnetic separation waste disposal process, with a value of 0.2~1.0.

[0015] Preferably, in step 4), the mathematical model for the magnetic field strength of the weak magnetic separation of fine-particle minerals is:

[0016] (II).

[0017] In the formula: H2 is the magnetic field strength during weak magnetic separation, GS. K2 is the magnetic field strength adjustment coefficient during weak magnetic separation, with a value of 100~500. S2 is the mass content of sulfur minerals in the fine-grained ore, %. M2 is the mass content of magnetite in the fine-grained ore, %. D2 is the average particle size of the fine-grained ore, mm. b2 is the average particle size adjustment index during the weak magnetic separation waste disposal process, with a value of 0.01~0.2.

[0018] Preferably, in step 2), the particle size of coarse and fine ore particles is detected by particle size sieving.

[0019] Preferably, in step 2), the content of sulfur minerals in coarse and fine-grained ore is detected by a sulfur mineral content detection method.

[0020] Preferably, in step 2), the content of magnetite in coarse and fine ore particles is detected by the chemical phase detection method of iron.

[0021] Preferably, in step 3), the strong magnetic separation is dry magnetic separation.

[0022] Preferably, in step 4), the weak magnetic separation is wet magnetic separation.

[0023] As a preferred option, the strong magnetic separation concentrate obtained in step 3) and the weak magnetic separation concentrate obtained in step 4) are further processed by any one of the following processes: magnetic separation, flotation, or roasting, to obtain magnetite concentrate.

[0024] Preferably, the strong magnetic separation tailings obtained in step 3) and the weak magnetic separation tailings obtained in step 4) are further processed by leaching to obtain sulfuric acid and acid production waste residue.

[0025] Preferably, the acid production waste residue is mixed into sulfur-containing magnetite raw material for recycling.

[0026] Preferably, in step 1), the crushing and screening specifically involves: first, using a jaw crusher to coarsely crush the sulfur-containing magnetite, and then using a cone crusher for medium crushing. Finally, the crushed ore is screened through a vibrating screen with a 3mm aperture, wherein the material over the screen is coarse-grained ore and the material under the screen is fine-grained ore.

[0027] In existing technologies, traditional beneficiation processes for sulfur-containing magnetite commonly suffer from sulfur residue and iron loss during magnetic separation and waste disposal, resulting in unsatisfactory sulfur-iron separation and low utilization rates of iron and sulfur resources. This is because factors such as ore particle size, magnetite content, and sulfur mineral content interfere with each other, making it difficult for traditional magnetic separation processes to achieve efficient separation of sulfur and iron. This leads to high sulfur content in iron concentrate and significant iron residue in tailings. This phenomenon is particularly pronounced in ores containing pyrrhotite, where conventional magnetic separation cannot distinguish the strong magnetic differences between magnetite and pyrrhotite, necessitating additional desulfurization and iron removal processes, significantly increasing production costs and process complexity. To address the shortcomings of traditional processes, the researchers of this invention conducted in-depth research and practice, particularly exploring the correlation between the physicochemical properties of ore and the iron-sulfur separation effect. They discovered that dynamically adjusting the magnetic field strength can effectively improve the separation accuracy. Based on this, by real-time detection of ore physicochemical parameters and the establishment of a magnetic field strength control model, precise adaptation of magnetic separation process parameters is achieved, thereby overcoming the limitations of the traditional fixed magnetic field strength mode. A mineral processing method based on raw material crushing, physicochemical property detection, and magnetic field strength control (i.e., CN121490883A) was proposed. Although this method improves the separation effect of sulfur and iron to a certain extent, when all crushed ore is subjected to magnetic separation together, due to the unavoidable presence of -3mm fine particles in the ore to be magnetically separated, a single magnetic field strength is difficult to adapt well to the magnetic separation process of the entire particle size ore. In particular, when there are large fluctuations in the -3mm fine particles, the calculated magnetic field strength is prone to being relatively high or low. When the magnetic field strength is too high, some weakly magnetic iron ores (mainly fine-grained iron ores) are enriched by magnetic separation, resulting in a decrease in the iron grade of the magnetic concentrate. When the magnetic field strength is too low, some iron ores with some magnetic properties (mainly coarse-grained iron ores) are not enriched by magnetic separation and end up in the tailings, resulting in a decrease in iron recovery rate.

[0028] To address the aforementioned issues, this invention, based on the above-mentioned solutions, conducted further practical research and discovered that -3mm particle size ore does not fully conform to the magnetic field strength control model of the above-mentioned solutions. Therefore, this invention proposes a graded magnetic separation concept, which involves pre-crushing and grading the ore, and independently and dynamically adjusting the magnetic field strength of the magnetic separation based on the characteristics of different particle size ore. This precisely controls the orientation of iron and sulfur minerals in coarse and fine particle ore, thereby optimizing the element orientation and achieving efficient separation of sulfur minerals and magnetite. This improves the grade of iron concentrate, reduces sulfur content, and simultaneously reduces the loss of iron minerals, thus improving the resource utilization rate of iron and sulfur.

[0029] In this invention, the graded magnetic separation process specifically includes the following steps: First, sulfur-containing magnetite is crushed and screened to obtain coarse-grained ore and fine-grained ore; then, the coarse-grained ore and fine-grained ore are subjected to characteristic analysis to obtain characteristic data including particle size, sulfur mineral content, and magnetite content; then, mathematical models for the magnetic field strength of strong magnetic separation of coarse-grained ore and weak magnetic separation of fine-grained ore are established respectively. Using the characteristic data of coarse and fine-grained ore as independent variables, different mathematical models are used to calculate the magnetic field strength during magnetic separation. Then, strong magnetic separation is performed on the coarse-grained ore to obtain strong magnetic separation concentrate (magnetite) and strong magnetic separation tailings (sulfur minerals), and weak magnetic separation is performed on the fine-grained ore to obtain weak magnetic separation concentrate (magnetite) and weak magnetic separation tailings (sulfur minerals). This graded magnetic separation method can fully consider the differences in the occurrence state of sulfur minerals and magnetite in different particle sizes of ore, avoiding the problem of incomplete separation when treating mixed particle sizes of ore with a single magnetic field strength. This effectively solves the technical problems of excessive sulfur content in iron concentrate and loss of iron minerals with tailings, and provides an economical and feasible process solution for the efficient utilization of sulfur-containing magnetite.

[0030] In this invention, crushing refers to reducing the ore size through mechanical force, specifically achieved using jaw crushers and cone crushers for staged crushing. The particle size of the crushed particles can be less than 30 mm. Characteristic analysis includes particle size detection, quantitative analysis of magnetic minerals, and sulfur content detection, specifically achieved using laser particle size analyzers, magnetic susceptibility meters, and X-ray fluorescence spectrometers. Magnetic field strength control involves establishing a mathematical model based on the ore particle size, magnetite content, and sulfur content parameters to dynamically calculate the optimal magnetic field strength value, specifically achieved through an electromagnetic coil current adjustment device.

[0031] In this invention, sulfur-containing magnetite undergoes multi-stage crushing and screening to produce coarse and fine particles with uniform particle size distribution. A detection system acquires characteristic data such as particle size distribution, magnetite content, and sulfur mineral content for each particle. Then, based on preset algorithms in their respective magnetic field strength mathematical models, the detection data is substituted into the corresponding models for calculation, and the magnetic separator's operating parameters are adjusted according to the calculation results. During magnetic separation, different magnetic minerals exhibit differentiated trajectories in the gradient magnetic field. Magnetite, due to its strong magnetism, is captured in the magnetite zone, while sulfur minerals, due to their weak magnetism, are discharged with the tailings. This process forms a closed-loop control through parameter feedback, ensuring that the magnetic field strength is always optimally matched to the ore characteristics.

[0032] In the high-intensity magnetic separation process of this invention, sulfur minerals in coarse-grained ore often exist in the form of inclusions or intergrowths. Furthermore, the magnetic difference between magnetite and sulfur minerals is relatively insignificant in the coarse-grained state. By setting a high magnetic field strength, it is ensured that sulfur mineral particles containing or intergrowing with magnetite can also be effectively adsorbed, thereby maximizing the recovery of iron minerals and reducing iron resource loss. For example, when the sulfur mineral content in the coarse-grained ore is high or the average particle size is large, the high-intensity magnetic field strength mathematical model (I) automatically calculates a higher magnetic field strength to overcome the separation difficulty caused by the inclusion or intergrowth of sulfur minerals with magnetite. In this dry high-intensity magnetic separation process, the ore passes through the magnetic field in a loose state, reducing the interference of the slurry on the separation and facilitating the effective separation of coarse-grained ore to obtain high-intensity magnetic concentrate and tailings. The high-intensity magnetic concentrate is mainly enriched in magnetite, while the high-intensity magnetic tailings mainly contain sulfur minerals and some gangue.

[0033] In the weak magnetic separation process of this invention, the fine-particle ore has a high degree of liberation of magnetite monomers and sulfur minerals exist mostly as monomers or micro-particle intergrowths. Using a lower magnetic field strength for wet magnetic separation is problematic because the fine-particle ore has a small particle size and large specific surface area. If the magnetic field strength is too high, a large amount of gangue minerals and sulfur minerals will be adsorbed into the concentrate, thus reducing the iron concentrate grade. Therefore, through the mathematical model (II) of the weak magnetic separation magnetic field strength, based on the sulfur mineral content, magnetite content, and average particle size of the fine-particle ore, a suitable low magnetic field strength is accurately calculated. This ensures effective recovery of magnetite while minimizing the mixing of sulfur minerals. In the wet weak magnetic separation process, the ore passes through the magnetic field in the form of a slurry. The fluidity of the slurry helps to fully disperse and separate the fine-particle magnetite from the gangue and sulfur minerals. The more magnetically charged magnetite particles are adsorbed by the magnetic separator to become the weak magnetic separation concentrate, while the less magnetically charged sulfur minerals and gangue are discharged with the slurry as weak magnetic separation tailings. This low-magnetic-strength wet magnetic separation, tailored to the characteristics of fine-grained ore, can significantly improve the grade of iron concentrate and reduce sulfur content.

[0034] Compared with existing technologies, this invention employs graded magnetic separation and individually adjusts the magnetic separation intensity of coarse and fine ore, which can accurately match the mineral characteristics of different particle sizes. This avoids the problem of fluctuating separation accuracy caused by differences in the magnetic behavior of coarse and fine particles when processing mixed particle sizes with a single magnetic field intensity. For coarse ore, magnetite and sulfur minerals often form inclusions or intergrowths within them, with relatively small magnetic differences. By establishing a mathematical model (I) for strong magnetic separation magnetic field intensity, and comprehensively considering key characteristic data such as sulfur mineral content (S1), magnetite content (M1), and average particle size (D1) of coarse ore, and introducing magnetic field intensity adjustment coefficients (K1), magnetite content adjustment coefficients (r1), and average particle size adjustment index (b1), a higher magnetic field intensity that can overcome inclusion or intergrowth structures and ensure maximum recovery of iron minerals is dynamically calculated, effectively reducing the loss of iron resources. For fine-grained ore, the magnetite monomers have a high degree of liberation, but the fine particles have a large specific surface area. If the magnetic field strength is too high, gangue and sulfur minerals are easily adsorbed. Therefore, through the mathematical model (II) of magnetic field strength for weak magnetic separation, based on the sulfur mineral content (S2), magnetite content (M2), average particle size (D2), magnetic field strength adjustment coefficient (K2), and average particle size adjustment index (b2) of the fine-grained ore, a lower magnetic field strength is accurately calculated. Under the premise of ensuring effective recovery of magnetite, the mixing of sulfur minerals is significantly reduced, and the grade of iron concentrate is improved. In addition, this invention uses dry strong magnetic separation for coarse-grained ore, and the ore passes through the magnetic field in a loose state, reducing slurry interference and facilitating the separation of coarse particles; for fine-grained ore, wet weak magnetic separation is used. The fluidity of the slurry promotes the full dispersion and separation of fine-grained magnetite from gangue and sulfur minerals, further optimizing the separation effect. Meanwhile, by merging strong magnetic separation concentrate and weak magnetic separation concentrate, high-quality magnetite concentrate can be obtained through further processing. The tailings of strong magnetic separation and weak magnetic separation can be leached to recover sulfuric acid and recycle the acid production waste residue, realizing the efficient and comprehensive utilization of iron and sulfur resources, reducing environmental pressure. The whole process has significant advantages such as process optimization, cost control, and high resource utilization.

[0035] The magnetic field strength adjustment coefficient K (including K1 and K2) refers to the parameter used to adjust the basic value of the magnetic field strength. This can be achieved by adjusting the operating current or the number of coil turns of the magnetic separator, and is used to match the magnetic separation requirements of different ore types. The sulfur mineral content S (including S1 and S2) refers to the mass percentage of sulfur ore in sulfur-bearing magnetite, which can be detected using X-ray fluorescence spectroscopy or chemical titration. This parameter reflects the degree of interference of sulfur minerals on the magnetic separation process. The magnetite content M (including M1 and M2) refers to the mass percentage of magnetite in the ore, which can be detected using a magnetic material content analyzer or chemical phase analysis. This parameter characterizes the enrichment degree of the target mineral in the ore. The magnetite content adjustment coefficient r1 is a proportional factor for adjusting the magnetic field strength according to the magnetite content, mainly used to balance the magnetic field strength requirements of high magnetite content. The average particle size D (including D1 and D2) refers to the geometric mean size of the ore particles, which can be determined using a laser particle size analyzer or sieving. This parameter characterizes the degree of ore crushing. The particle size adjustment index b (including b1 and b2) refers to the nonlinear coefficient of the effect of particle size on magnetic field strength, which is mainly used to reflect the differences in the motion characteristics of particles of different sizes in a magnetic field.

[0036] In step 1) of this invention, the sulfur-containing magnetite ore generally needs to be pre-treated before crushing to remove large pieces of waste rock and metallic impurities mixed in the ore, in order to prevent damage to the crushing equipment. The pre-treatment process can be carried out by manual sorting or preliminary separation using a drum screen. The sorted ore is then evenly fed into the feed inlet of a jaw crusher via a belt conveyor. The jaw crusher employs a deep-cavity design, with the angle between the moving jaw and the fixed jaw controlled at 20-25 degrees to improve crushing efficiency and the ore crushing ratio. The discharge port size can be adjusted according to the feeding requirements of the subsequent cone crusher, typically set to 50-100 mm. A Simons cone crusher is selected, employing the principle of layered crushing. The particle size of the ore after medium crushing is controlled by adjusting the gap between the crushing wall and the jaw wall. The maximum particle size of the ore after medium crushing is controlled within 50 mm to ensure uniform particle size of the ore entering the vibrating screen. The vibrating screen uses a double-layer vibrating screen. The upper screen has a 30mm mesh size and is used to separate ultra-coarse particles, which are then returned to the cone crusher for further crushing. The lower screen has a 3mm mesh size and achieves the final separation of coarse and fine particles. During the screening process, to reduce material adhesion to the screen surface, the screen surface is made of polyurethane and undergoes a special anti-slip treatment. Spring damping devices are also installed on both sides of the screen to reduce vibration noise during screening, keeping the noise level below 85 decibels. For materials with high moisture content, a preheating device can be used to heat the material to 40-50℃ before screening to reduce its stickiness and further improve the screening effect. This grading method effectively separates materials of different particle sizes, laying the foundation for subsequent differentiated magnetic separation based on the characteristics of different particle sizes.

[0037] In step 2) of this invention, the coarse and fine ore particles obtained in step 1) are subjected to characteristic analysis. For the coarse ore particles, a laser particle size analyzer or particle size sieve analysis is used to detect their particle size distribution, focusing on the proportion of particles in the 3mm to 30mm range and the average particle size (D1). The content of magnetite (M1) is accurately determined using a magnetic susceptibility analyzer combined with chemical phase analysis. The sulfur content (S1) is obtained by quantitative analysis of the sulfur element in the ore using X-ray fluorescence spectrometry. For the fine ore particles, the particle size distribution is also detected using a laser particle size analyzer or particle size sieve analysis, focusing on the particle distribution characteristics and average particle size (D2) within the -3mm particle size range. The magnetite content (M2) is quickly determined using a magnetic content analyzer. The sulfur content (S2) is determined by X-ray fluorescence spectrometry or high-precision chemical titration. During the characteristic analysis process, to ensure the accuracy and representativeness of the data, each type of ore must be tested at least three times in parallel, and the average value is taken as the final characteristic data. These characteristic data will serve as key input parameters for establishing a mathematical model of magnetic field strength and calculating the optimal magnetic field strength, directly affecting the precise control of the magnetic separation process and the final sorting effect.

[0038] Particle size distribution screening refers to the method of classifying and screening particulate materials using standard sieves to determine their particle size distribution. Specifically, this can be achieved using multi-layer vibrating screens or rotary screens with sieves of different aperture sizes. After each stage of screening, the mass of particles remaining on each sieve layer is weighed to calculate the average particle size. This screening process directly reflects the actual physical size of the particles, providing fundamental parameters for adjusting the magnetic field strength in subsequent magnetic separation processes, ensuring that the magnetic field waste removal process matches the material particle size. Specifically, after the raw material crushing process, the obtained coarse or fine ore samples are placed in a screening device and classified and screened according to preset sieve specifications. During screening, particles larger than the sieve aperture size are retained on the sieve, while particles smaller than the aperture size pass through to the next layer. By recording the particle mass percentage of each sieve layer and combining it with the sieve aperture size data, the average particle size of the material can be calculated. This data, along with the sulfur mineral content and magnetite content, is input into the mathematical model of strong or weak magnetic separation magnetic field strength to dynamically adjust the operating parameters of the magnetic separation equipment, thereby optimizing the magnetic separation efficiency.

[0039] The chemical phase detection method for iron utilizes the selective solubility characteristics of different chemical reagents for the occurrence forms of iron, determining the content of magnetite through stepwise dissolution and quantitative analysis. Specifically, acidic solutions such as hydrochloric acid, sulfuric acid, or nitric acid are used to leach the sample in stages. The iron content in the dissolved solution is then measured using atomic absorption spectroscopy or inductively coupled plasma atomic emission spectroscopy, thus distinguishing the proportion of magnetite from other iron-bearing minerals. This method achieves mineral phase separation through the difference in chemical dissolution, avoiding interference from the mineral embedding morphology during physical separation. Specifically, in the beneficiation of sulfur-containing magnetite, the magnetite content directly affects the magnetic field strength setting of the magnetic separation process. The chemical phase detection method for iron can accurately distinguish the occurrence state of iron in magnetite from sulfur-containing iron minerals such as pyrrhotite and ferrite. For example, under acidic conditions, pyrrhotite dissolves preferentially while magnetite remains stable. By controlling the dissolution conditions and measuring the iron content in stages, the proportion of magnetite can be quantitatively calculated. This detection result provides accurate input parameters for subsequent magnetic field strength calculations, ensuring that the magnetic separation process effectively separates the target mineral.

[0040] The sulfur mineral content detection method refers to the quantitative analysis of the existence form and content ratio of sulfur element in minerals through chemical or physical means. Specifically, it can be achieved by combining X-ray diffraction analysis with chemical phase analysis. By identifying the crystal structure characteristics and elemental composition of sulfur minerals, different sulfide types such as pyrite and pyrrhotite can be distinguished and their mass fractions calculated. This detection method can accurately quantify the actual content of sulfur minerals, providing data support for the dynamic adjustment of subsequent magnetic separation process parameters. Specifically, in the implementation of the sulfur mineral content detection method, the crushed sulfur-containing magnetite sample is first ground and prepared. Then, the sample is scanned with an X-ray diffractometer, and the types and relative proportions of sulfur minerals are determined by matching characteristic peaks. Further, the total sulfur content is determined by chemical titration or inductively coupled plasma atomic emission spectrometry, and the actual content of each sulfur mineral is calculated by combining the phase analysis results. Through this detection process, the content distribution data of different sulfur minerals such as pyrite and pyrrhotite can be accurately obtained, providing key input parameters for the magnetic field strength calculation model.

[0041] This invention further proposes to further process the concentrate (magnetite) obtained from strong and weak magnetic separation through any one of the following steps: magnetic separation, flotation, or roasting, to obtain magnetite concentrate: After preliminary magnetic separation, based on the sulfur residue and iron grade in the strong and / or weak magnetic separation concentrates, secondary magnetic separation is selected to enhance the enrichment of magnetic minerals, or flotation is used to preferentially remove sulfides coated on the surface of magnetite particles, or sulfur minerals are completely decomposed in a high-temperature roasting process. For example, when the sulfur content in the strong and / or weak magnetic separation concentrates is high and the sulfur exists in the form of pyrrhotite, flotation can be preferentially used. By adjusting the pH of the pulp to the acidic range and adding xanthate collectors, pyrrhotite and magnetite can be selectively separated. This forms a multi-process synergistic graded processing mechanism, effectively solving the problem that a single magnetic separation process is insufficient to completely separate magnetite and sulfur minerals.

[0042] This invention further proposes to process the tailings (sulfur-containing ore) obtained from strong and weak magnetic separation through a leaching process to obtain sulfuric acid and acid production waste residue. The leaching process involves selectively dissolving sulfur in sulfur minerals using chemical solvents, specifically by soaking the sulfur-containing ore in a dilute sulfuric acid solution. The acidic environment induces a chemical reaction in the sulfur minerals, generating soluble sulfates. Sulfuric acid is the product formed after concentrating and purifying the sulfur-containing compound solution generated during the leaching reaction; it can be obtained by evaporation and crystallization from the leachate. The acid production waste residue refers to the solid material remaining after the leaching reaction, mainly containing unreacted iron minerals and silicate impurities. This residue can be separated from the leachate through a solid-liquid separation process. Specifically, the leaching process involves mixing the sulfur-containing ore with an acidic solution and reacting it at a specific temperature, converting the sulfur in the sulfur minerals into soluble sulfates that enter the liquid phase. After the reaction, the leachate and solid residue are separated by filtration or centrifugation. After evaporation and concentration, the leachate yields sulfuric acid. The solid residue has a high iron mineral content and can be recycled back into the mineral processing stage. This process achieves efficient sulfur extraction through chemical dissolution, avoiding gas pollution problems caused by high-temperature roasting. In some specific embodiments, a 5-30% sulfuric acid solution can be used as the acidic solution, and the reaction temperature can be controlled within the range of 50-90°C. The leaching reaction time can be dynamically adjusted according to the sulfur mineral content; for example, when the sulfur content is high, the reaction time can be extended to 2-4 hours. After dehydration and drying, the sulfuric acid waste residue can be mixed with newly added sulfur-containing magnetite raw material and re-entered into the crushing and screening process for mineral processing.

[0043] This invention further proposes a method of mixing acid production waste residue into sulfur-containing magnetite raw materials for cyclic beneficiation. The acid production waste residue refers to the solid waste generated during the roasting of pyrite to produce acid, containing iron, sulfur, and silicon-phosphorus impurities. Specifically, it can be the residue from the roasting of pyrite in the sulfuric acid production process. This waste residue has a high iron content but excessive impurities, making it unsuitable for direct iron smelting. Circular beneficiation refers to re-inputting the acid production waste residue as raw material into the beneficiation process. Specifically, this can be achieved by crushing and screening the waste residue, mixing it with the original sulfur-containing magnetite, and then entering a magnetic separation process. Through further separation, residual iron and sulfur minerals can be extracted from the waste residue. Specifically, the acid production waste residue, after crushing and screening, is mixed with the original sulfur-containing magnetite raw material in a certain proportion and then enters the magnetic separation waste disposal process. Under the control of a mathematical model of magnetic field strength, the magnetite and sulfur minerals in the waste residue are separated and recovered. Waste residue that is not separated can be returned to the process for recycling. This process reduces waste residue accumulation and lowers raw material consumption by reusing valuable components in the waste residue.

[0044] It should be noted that all models or formulas in this invention were fitted by the inventor based on experimental and engineering applications. All calculations are obtained by converting values ​​to specified units and substituting the converted values ​​into the formulas (after unit conversion, only the values ​​are substituted into the formulas, not the units; the units are only used to adjust the magnitude of the values. It should be noted that "%" is not used as a unit but is substituted into the formulas for calculation; for example, 21% has a value of 0.21 when substituted into the formulas).

[0045] Compared with the prior art, the technical solution provided by the present invention has the following beneficial technical effects:

[0046] 1. This invention achieves differentiated separation of coarse and fine-grained magnetite through graded magnetic separation, effectively avoiding the low separation efficiency caused by particle size differences in traditional single magnetic separation processes. For coarse-grained magnetite, dry high-intensity magnetic separation is used, utilizing its loose state and the characteristics of passing through the magnetic field to reduce slurry interference and significantly improve the separation effect of coarse-grained magnetite from gangue and sulfur minerals. For fine-grained magnetite, wet low-intensity magnetic separation is used, leveraging the good fluidity of the slurry to promote the full dispersion and effective separation of fine-grained magnetite. This graded magnetic separation strategy not only optimizes the separation accuracy but also significantly improves the grade and recovery rate of iron concentrate.

[0047] 2: This invention establishes mathematical models for strong and weak magnetic field strengths and introduces key parameters such as magnetic field strength adjustment coefficient, sulfur mineral content, magnetite content, average particle size, and particle size adjustment index to achieve precise control of the magnetic separation process, ensuring that ores of different types and characteristics can achieve optimal separation conditions.

[0048] 3. This invention also comprehensively recovers iron and sulfur from magnetic separation concentrate and tailings, reducing the environmental pressure caused by solid waste emissions. The entire process has multiple advantages, including scientific and reasonable process design, controllable operating costs, high resource utilization rate, and significant environmental benefits, providing a practical solution for the efficient and clean utilization of sulfur-containing magnetite. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the graded magnetic separation process described in this invention. Detailed Implementation

[0050] The technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0051] Example 1

[0052] A grading magnetic separation process for sulfur-containing magnetite, the grading magnetic separation process comprising:

[0053] 1) The sulfur-containing magnetite is crushed and screened to obtain coarse and fine ore particles.

[0054] 2) Perform characteristic analysis on coarse and fine ore particles respectively to obtain characteristic data of coarse and fine ore particles, including particle size, sulfur mineral content and magnetite content.

[0055] 3) Establish a mathematical model for the magnetic field strength of strong magnetic separation of coarse-grained ore. Using the characteristic data of coarse-grained ore as independent variables, the magnetic field strength of coarse-grained ore during strong magnetic separation is calculated through this mathematical model. After the strong magnetic separation is completed, strong magnetic concentrate and strong magnetic tailings are obtained.

[0056] 4) Establish a mathematical model for the magnetic field strength of weak magnetic separation of fine-particle minerals. Using the characteristic data of fine-particle minerals as independent variables, the magnetic field strength of the fine-particle minerals during weak magnetic separation is calculated through this mathematical model. After the weak magnetic separation is completed, weak magnetic concentrate and weak magnetic tailings are obtained.

[0057] Example 2

[0058] Repeat Example 1, except that in step 1), the particle size range of the coarse ore is 3~30mm, and the particle size range of the fine ore is ≤3mm.

[0059] Example 3

[0060] Repeat Example 2, except that in step 3), the mathematical model for the magnetic field strength of the coarse-grained ore in strong magnetic separation is:

[0061] (I).

[0062] In the formula: H1 is the magnetic field strength during strong magnetic separation, GS. K1 is the magnetic field strength adjustment coefficient during strong magnetic separation, with a value of 3000. S1 is the mass content of sulfur minerals in the coarse-grained ore, %. M1 is the mass content of magnetite in the coarse-grained ore, %. r1 is the magnetite content adjustment coefficient, with a value of 0.1. D1 is the average particle size of the coarse-grained ore, mm. b1 is the average particle size adjustment index during the strong magnetic separation waste disposal process, with a value of 0.3.

[0063] Example 4

[0064] Repeat Example 2, except that in step 4), the mathematical model for the magnetic field strength of the weak magnetic separation of fine-particle minerals is:

[0065] (II).

[0066] In the formula: H2 is the magnetic field strength during weak magnetic separation, GS. K2 is the magnetic field strength adjustment coefficient during weak magnetic separation, with a value of 400. S2 is the mass content of sulfur minerals in the fine-grained ore, %. M2 is the mass content of magnetite in the fine-grained ore, %. D2 is the average particle size of the fine-grained ore, mm. b2 is the average particle size adjustment index during the weak magnetic separation waste disposal process, with a value of 0.05.

[0067] Example 5

[0068] Repeat Example 4, except that in step 2), the particle size of coarse and fine ore particles is detected by particle size sieving.

[0069] Example 6

[0070] Repeat Example 5, except that in step 2), the content of sulfur minerals in coarse and fine-grained ore is detected by a sulfur mineral content detection method.

[0071] Example 7

[0072] Repeat Example 6, except that in step 2), the content of magnetite in coarse and fine ore particles is detected by the chemical phase detection method of iron.

[0073] Example 8

[0074] Repeat Example 7, except that in step 3), the strong magnetic separation is dry magnetic separation.

[0075] Example 9

[0076] Repeat Example 8, except that in step 4), the weak magnetic separation is wet magnetic separation.

[0077] Example 10

[0078] Repeat Example 9, except that the strong magnetic separation concentrate obtained in step 3) and the weak magnetic separation concentrate obtained in step 4) are further processed by any one of the following processes: magnetic separation, flotation, or roasting, to obtain magnetite concentrate.

[0079] Example 11

[0080] Repeat Example 10, except that the strong magnetic separation tailings obtained in step 3) and the weak magnetic separation tailings obtained in step 4) are further processed by leaching to obtain sulfuric acid and acid production waste residue.

[0081] Example 12

[0082] Repeat Example 11, except that the acid production waste residue is mixed into sulfur-containing magnetite raw material for recycling.

[0083] Example 13

[0084] Repeat Example 9, except that in step 1), the crushing and screening are specifically performed as follows: first, a jaw crusher is used to coarsely crush the sulfur-containing magnetite, and then a cone crusher is used for medium crushing. Finally, the crushed ore is screened through a vibrating screen with a 3mm aperture, wherein the material over the screen is coarse ore and the material under the screen is fine ore.

[0085] Application Example 1

[0086] The method described in Example 13 is used to perform graded magnetic separation of sulfur-containing magnetite:

[0087] Sulfur-bearing magnetite raw material: a sulfur-bearing magnetite mine in Hubei Province.

[0088] After crushing and screening, sulfur-containing magnetite is used to obtain coarse and fine particles. The average particle size of the coarse particles is about 10.2 mm, and the average particle size of the fine particles is about 1.7 mm.

[0089] Analysis of coarse-grained ore characteristics: The mass content of sulfur minerals in coarse-grained ore is approximately 21%, and the mass content of magnetite in coarse-grained ore is approximately 65%.

[0090] Based on the obtained coarse-grained ore characteristic data, the magnetic field strength H1 during strong magnetic separation is calculated using a mathematical model of the strong magnetic separation magnetic field strength. Under the current operating conditions, the magnetic field strength adjustment coefficient K1 during strong magnetic separation is taken as 3000, the mass content of sulfur minerals S1 in the coarse-grained ore is approximately 21%, the mass content of magnetite M1 in the coarse-grained ore is approximately 65%, the magnetite content adjustment coefficient r1 is taken as 0.1, and the average particle size adjustment index b1 during the strong magnetic separation waste disposal process is taken as 0.3; therefore:

[0091] .

[0092] The magnetic field strength was controlled at 4767.4 GS during the high-intensity magnetic separation process for coarse-grained ore to obtain high-intensity magnetic concentrate and tailings. Analysis showed that the iron content of the high-intensity magnetic concentrate was approximately 65.2%, the sulfur content was approximately 0.31%, and the iron content of the high-intensity magnetic tailings was approximately 12.3%.

[0093] Analysis of the characteristics of fine-grained minerals: The mass content of sulfur minerals in fine-grained minerals is approximately 18%, and the mass content of magnetite in fine-grained minerals is approximately 69%.

[0094] Based on the detected fine-grained ore characteristic data, the magnetic field strength H2 during weak magnetic separation is calculated using a mathematical model of the weak magnetic separation magnetic field strength. Under the current operating conditions, the magnetic field strength adjustment coefficient K2 during weak magnetic separation is set to 400. The mass content of sulfur minerals S2 in the fine-grained ore is approximately 18%, the mass content of magnetite M2 in the fine-grained ore is approximately 69%, and the average particle size adjustment index b2 during the weak magnetic separation waste disposal process is set to 0.05. Therefore:

[0095] .

[0096] The magnetic field strength was controlled at 801.5 GS during the weak magnetic separation process of fine-particle ore to obtain weak magnetic concentrate and tailings. Analysis showed that the iron content of the obtained weak magnetic concentrate was approximately 67.3%, the sulfur content was approximately 0.15%, and the iron content of the obtained weak magnetic tailings was approximately 11.2%.

Claims

1. A graded magnetic separation process for sulfur-containing magnetite, characterized in that: The graded magnetic separation process includes: 1) The sulfur-containing magnetite is crushed and screened to obtain coarse and fine ore particles; 2) Perform characteristic analysis on coarse and fine ore particles respectively to obtain characteristic data of coarse and fine ore particles, including particle size, sulfur mineral content and magnetite content. 3) Establish a mathematical model for the magnetic field strength of strong magnetic separation of coarse-grained ore. Using the characteristic data of coarse-grained ore as independent variables, the magnetic field strength of coarse-grained ore during strong magnetic separation is calculated through this mathematical model. After the strong magnetic separation is completed, strong magnetic concentrate and strong magnetic tailings are obtained. 4) Establish a mathematical model for the magnetic field strength of weak magnetic separation of fine-particle minerals. Using the characteristic data of fine-particle minerals as independent variables, the magnetic field strength of the fine-particle minerals during weak magnetic separation is calculated through this mathematical model. After the weak magnetic separation is completed, weak magnetic concentrate and weak magnetic tailings are obtained.

2. The graded magnetic separation process according to claim 1, characterized in that: In step 1), the particle size range of the coarse ore is 3~30mm; the particle size range of the fine ore is ≤3mm.

3. The graded magnetic separation process according to claim 1 or 2, characterized in that: In step 3), the mathematical model for the magnetic field strength of the strong magnetic separation of coarse-grained ore is: （I）； In the formula: H1 is the magnetic field strength during strong magnetic separation, GS; K1 is the magnetic field strength adjustment coefficient during strong magnetic separation, with a value of 3000~4000; S1 is the mass content of sulfur minerals in coarse-grained ore, % M1 is the mass content of magnetite in coarse-grained ore, %; r1 is the magnetite content adjustment coefficient, with a value of 0.01~0.5; D1 is the average particle size of coarse-grained ore, mm; b1 is the average particle size adjustment index of the strong magnetic separation waste disposal process, with a value of 0.2~1.

0.

4. The graded magnetic separation process according to any one of claims 1-3, characterized in that: In step 4), the mathematical model for the magnetic field strength of the weak magnetic separation of fine-particle minerals is as follows: (II); In the formula: H2 is the magnetic field strength during weak magnetic separation, GS; K2 is the magnetic field strength adjustment coefficient during weak magnetic separation, with a value of 100~500; S2 is the mass content of sulfur minerals in fine-grained ore, %; M2 is the mass content of magnetite in fine-grained ore, %; D2 is the average particle size of fine-grained ore, mm; b2 is the average particle size adjustment index during the waste disposal process of weak magnetic separation, with a value of 0.01~0.

2.

5. The graded magnetic separation process according to any one of claims 1-4, characterized in that: In step 2), the particle size of coarse and fine ore particles is determined by particle size analysis; and / or In step 2), the content of sulfur minerals in coarse-grained and fine-grained ore is determined by a sulfur mineral content detection method; and / or In step 2), the content of magnetite in coarse and fine-grained ore is determined by the chemical phase detection method of iron.

6. The graded magnetic separation process according to any one of claims 1-5, characterized in that: In step 3), the strong magnetic separation is dry magnetic separation; and / or In step 4), the weak magnetic separation is a wet magnetic separation.

7. The graded magnetic separation process according to any one of claims 1-6, characterized in that: The strong magnetic separation concentrate obtained in step 3) and the weak magnetic separation concentrate obtained in step 4) are further processed through any one of the following processes: magnetic separation, flotation, or roasting, to obtain magnetite concentrate.

8. The graded magnetic separation process according to any one of claims 1-7, characterized in that: The strong magnetic separation tailings obtained in step 3) and the weak magnetic separation tailings obtained in step 4) are further processed by leaching to obtain sulfuric acid and acid production waste residue.

9. The graded magnetic separation process according to claim 8, characterized in that: The acid production waste residue is mixed into sulfur-containing magnetite raw material for recycling.

10. The graded magnetic separation process according to any one of claims 1-9, characterized in that: In step 1), the crushing and screening are specifically as follows: first, a jaw crusher is used to coarsely crush the sulfur-containing magnetite, and then a cone crusher is used for medium crushing; finally, the crushed ore is screened through a vibrating screen with a 3mm aperture, wherein the material on the screen is coarse ore and the material under the screen is fine ore.

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