A method for recovering superfine weakly magnetic hematite from bayer process red mud magnetic separation tailings

Abstract

This application discloses a method for recovering ultrafine weakly magnetic hematite from Bayer process red mud magnetic separation tailings, comprising the following steps: providing Bayer process red mud magnetic separation tailings with a particle size D50 of 10μm~20μm, iron-bearing minerals including weakly magnetic hematite, and gangue minerals containing 55%~60% aluminosilicates and 0~20% calcite; mixing the Bayer process red mud magnetic separation tailings with water and adding an inorganic dispersant for stirring and dispersion to obtain a dispersed slurry, the inorganic dispersant including a first dispersant and a second dispersant, the first dispersant including sodium pyrophosphate and / or water glass, the second dispersant including sodium hexametaphosphate and / or sodium tripolyphosphate, the mass ratio of the first dispersant and the second dispersant being (1~3):(1~3); subjecting the dispersed slurry to high gradient magnetic separation under a background field strength of not less than 1.5 T, collecting the concentrate as hematite rough concentrate, and collecting the tailings as beneficiation tailings. This method improves the TFe grade of hematite rough and concentrate and the recovery rate of hematite.

Description

Technical Field

[0001] This application relates to the field of comprehensive utilization technology of red mud resources, and in particular to a method for recovering ultrafine weakly magnetic hematite from the tailings of Bayer process red mud magnetic separation. Background Technology

[0002] Red mud is an industrial waste generated during alumina production. Approximately 0.8 to 1.5 tons of red mud are produced for every ton of alumina produced. Bayer process red mud, due to its large production volume and high iron content (typically 20% to 40% TFe), has significant iron resource recovery value. Currently, iron recovery from Bayer process red mud mainly employs magnetic separation. However, because the iron minerals in red mud are mostly ultrafine-grained, weakly magnetic hematite (particle size often less than 20 μm), conventional magnetic separation processes have limited recovery efficiency, resulting in a large amount of iron resources remaining in the magnetic separation tailings (TFe can reach over 30%), causing a serious waste of iron resources.

[0003] To improve the recovery efficiency of ultrafine hematite, related technologies often employ a combination of "flotation reagent-assisted" and "magnetic separation" processes. For example, organic collectors such as oleic acid and kerosene are added to achieve hydrophobic agglomeration of the hematite, or inorganic dispersants are added to improve the dispersion of the slurry, followed by magnetic separation or flotation recovery. However, organic reagents enter the Bayer process alumina main flow with the tailings or slurry after beneficiation, leading to problems such as reduced alumina dissolution rate, severe foaming in the decomposition tank, finer aluminum hydroxide particle size, and filtration difficulties. Long-term accumulation can even pollute the entire alumina production system, hindering industrial application. Inorganic dispersants, on the other hand, have poor adaptability. The gangue composition of red mud tailings varies significantly among different alumina plants, making precise dispersion difficult with inorganic dispersants, especially for calcite-containing or high-aluminosilicate red mud tailings. Summary of the Invention This application provides a method for recovering ultrafine weakly magnetic hematite from Bayer process red mud magnetic separation tailings, solving one of the technical problems of poor dispersion effect on calcite-containing red mud tailings or high silicate aluminate red mud tailings.

[0004] A first aspect of this application provides a method for recovering ultrafine weakly magnetic hematite from Bayer process red mud magnetic separation tailings, comprising the following steps: providing Bayer process red mud magnetic separation tailings, wherein the particle size D50 of the Bayer process red mud magnetic separation tailings is 10μm~20μm, the iron-containing minerals in the Bayer process red mud magnetic separation tailings include weakly magnetic hematite, and the gangue minerals include 55%~60% aluminosilicates and 0~20% calcite; mixing the Bayer process red mud magnetic separation tailings with water to obtain a slurry with a mass concentration of 20%~30%; adding an inorganic dispersant to the slurry and stirring to disperse it to obtain a dispersed slurry, wherein the inorganic dispersant includes a first dispersant and a second dispersant, the first dispersant includes sodium pyrophosphate and / or water glass, the second dispersant includes sodium hexametaphosphate and / or sodium tripolyphosphate, the mass ratio of the first dispersant to the second dispersant is (1~3):(1~3), and the amount of the inorganic dispersant added is 1% based on dry tailings. kg / t ~4 kg / t; and subjecting the dispersed slurry to high-gradient magnetic separation under a background field strength of not less than 1.5 T, collecting the concentrate as hematite rough concentrate and the tailings as beneficiation tailings.

[0005] Optionally, the first dispersant is water glass, and the second dispersant is sodium hexametaphosphate, wherein the mass ratio of the water glass to the sodium hexametaphosphate is (1~3):1; and / or, The step of adding an inorganic dispersant to the slurry for stirring and dispersion includes first adding water glass for first stirring, and then adding sodium hexametaphosphate for second stirring. The first stirring speed is 600 rpm to 800 rpm and the first stirring time is 5 min to 6 min. The second stirring speed is 600 rpm to 800 rpm and the second stirring time is 8 min to 10 min.

[0006] Optionally, the first dispersant is sodium pyrophosphate, the second dispersant is sodium hexametaphosphate, and the mass ratio of the sodium pyrophosphate to the sodium hexametaphosphate is (1~3):3; and / or, In the step of adding an inorganic dispersant to the slurry and stirring to disperse it, sodium pyrophosphate and sodium hexametaphosphate are added simultaneously. The stirring time is 10 min to 15 min, and the stirring speed is 600 rpm to 800 rpm.

[0007] Optionally, the first dispersant is water glass, and the second dispersant is sodium tripolyphosphate, wherein the mass ratio of the water glass to the sodium tripolyphosphate is (0.5~1.5); and / or, The step of adding an inorganic dispersant to the slurry and stirring to disperse it includes first adding sodium tripolyphosphate for a third stirring, and then adding water glass for a fourth stirring. The third stirring speed is 600 rpm to 800 rpm and the third stirring time is 5 min to 6 min. The fourth stirring speed is 600 rpm to 800 rpm and the fourth stirring time is 8 min to 10 min.

[0008] Optionally, the high gradient magnetic separation process includes a first coarse separation, a first scan, and a second scan, wherein the background field strength of the first coarse separation is 1.5 T ~ 1.6 T, the background field strength of the first scan is 1.7 T ~ 1.8 T, and the background field strength of the second scan is 1.6 T ~ 1.7 T.

[0009] Optionally, the magnetic separation equipment for the high gradient magnetic separation process is a vertical ring high gradient magnetic separator, wherein the magnetic separation medium in the vertical ring high gradient magnetic separator is stainless steel wool with a diameter of 0.1 mm to 0.2 mm, and the filling rate of the stainless steel wool is 8% to 12%.

[0010] Optionally, the slurry flow rate of the high gradient magnetic separation treatment is 0.8 m / min ~ 1.2 m / min.

[0011] Optionally, the magnetic separation temperature of the high gradient magnetic separation process is 20℃~25℃.

[0012] Optionally, after the steps of performing high-gradient magnetic separation on the dispersed slurry under a background field strength of not less than 1.5 T, collecting the concentrate as hematite rough concentrate, and collecting the tailings as beneficiation tailings, the method further includes adjusting the pH of the beneficiation tailings to 10-12 using a pH adjuster, and controlling the residual amount of the inorganic dispersant in the beneficiation tailings to ≤60mg / L before sending it to the sedimentation process of Bayer process alumina production.

[0013] Optionally, the pH adjuster is waste alkaline solution generated during the Bayer process of alumina production.

[0014] Optionally, after the steps of performing high-gradient magnetic separation on the dispersed slurry under a background field strength of not less than 1.5 T, collecting the concentrate as hematite rough concentrate, and collecting the tailings as beneficiation tailings, the method further includes performing fine magnetic separation on the hematite rough concentrate, wherein the background field strength of the fine magnetic separation is 1.4T~1.5T, and the fine magnetic separation time is 3 min~5 min, to obtain hematite concentrate.

[0015] Optionally, the TFe grade of the Bayer process red mud magnetic separation tailings is less than 35%.

[0016] Compared with the prior art, the technical solution provided in this application has the following beneficial effects: The method for recovering ultrafine weakly magnetic hematite from Bayer process red mud magnetic separation tailings disclosed in this application uses Bayer process red mud magnetic separation tailings as raw material, with a particle size D50 of 10μm~20μm. The main iron-bearing mineral component is weakly magnetic hematite, and the gangue minerals contain 55%~60% aluminosilicates and 0~20% calcite. Then, the Bayer process red mud magnetic separation tailings are prepared into a slurry with a mass concentration of 20%~30%, and 1 kg / t~4 kg / t (based on dry tailings) of a specific inorganic dispersant (including a first dispersant and a second dispersant) is added to the slurry. After dispersion, high-gradient magnetic separation is performed under a background field strength of not less than 1.5 T, thereby achieving the recovery of ultrafine (particle size D50 of 10μm~20μm) hematite. A specific inorganic dispersant (including a first dispersant and a second dispersant) of 1 kg / t to 4 kg / t (based on dry tailings) works synergistically within a specific concentration window (20% to 30% mass concentration of slurry). It can effectively disperse ultrafine mineral particles (D50 of 10 μm to 20 μm) without the addition of any organic reagents, achieving effective dispersion of solid particles in tailings with different compositions (gangue minerals containing 55% to 60% aluminosilicates and 0 to 20% calcite). At the same time, combined with high-gradient strong magnetic separation treatment under specific conditions (background field strength not less than 1.5 T), iron-bearing minerals are separated from gangue minerals, achieving efficient enrichment of weakly magnetic hematite, improving the TFe grade of hematite rough concentrate and the recovery rate of hematite. Specifically, in a slurry with a mass concentration of 20%–30%, the solid particles have a suitable interaction distance. This ensures that the inorganic dispersant can fully act on the surface of the solid particles, while also providing sufficient space for the solid particles to move and disperse fully in response to the dispersing effect of the inorganic dispersant, forming a stable dispersion system. This also provides the necessary separation fluid conditions for high-gradient magnetic separation, facilitating more uniform passage of solid particles through the separation process, thereby synergistically improving the TFe grade of hematite rough and concentrate and the recovery rate of hematite. The inorganic dispersant includes a first dispersant and a second dispersant. The first dispersant includes sodium pyrophosphate and / or water glass, and the second dispersant includes sodium hexametaphosphate and / or sodium tripolyphosphate. The first dispersant can first act on Ca²⁺. + Eliminate Ca² +The inorganic dispersant has a negative impact on the dispersion system and simultaneously provides electrostatic repulsion or steric hindrance effect on the surface of solid particles adsorbed on the Bayer process red mud magnetic separation tailings. The second dispersant can stabilize the surface of solid particles on the Bayer process red mud magnetic separation tailings, while providing steric hindrance effect or stronger electrostatic repulsion. The two work synergistically to break the heterogeneous agglomeration of iron-bearing minerals and gangue minerals at a pulp concentration of 20%~30%, achieving the individual dissociation of all solid particles in ultrafine Bayer process red mud magnetic separation tailings (particle size D50 of 10μm~20μm). Furthermore, the dual effect of electrostatic repulsion combined with steric hindrance effectively solves the dispersion attenuation problem of the pulp under the dynamic conditions of high gradient strong magnetic separation, thereby improving the TFe grade of hematite rough and concentrate and the recovery rate of hematite. The dosage of inorganic dispersant is 1kg / t~4 kg / t can fully utilize the inorganic dispersant and solid particles in the Bayer process red mud magnetic separation tailings, thereby achieving the individual dissociation of all solid particles and improving the TFe grade of hematite rough concentrate and the recovery rate of hematite. In addition, the background field strength of not less than 1.5 T in the high gradient strong magnetic separation treatment can ensure that the magnetic medium is fully magnetized and generate a sufficiently high magnetic field gradient, which can effectively capture magnetic particles in the Bayer process red mud magnetic separation tailings with a particle size D50 of 10μm~20μm, thereby improving the TFe grade of hematite rough concentrate and the recovery rate of hematite.

[0017] This method is simple, energy-efficient, widely adaptable, and highly industrially applicable. It achieves secondary recovery of iron resources from red mud tailings while avoiding interference with the main alumina process, thus possessing significant economic, environmental, and industrial application value. Attached Figure Description

[0018] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and disclosure, and together with the description serve to explain the principles of this application and disclosure.

[0019] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic flowchart of a method for recovering ultrafine weakly magnetic hematite from Bayer process red mud magnetic separation tailings according to some embodiments of this application. Figure 2 This is a schematic flowchart of a method for recovering ultrafine weakly magnetic hematite from Bayer process red mud magnetic separation tailings according to some embodiments of this application. Figure 3This is a schematic flowchart of a method for recovering ultrafine weakly magnetic hematite from Bayer process red mud magnetic separation tailings according to some other embodiments of this application. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments 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, 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.

[0022] Any method steps, processes, and operations described in this application should not be construed as necessarily requiring them to be performed in a specific order as discussed or shown, unless explicitly specified. It should also be understood that additional or alternative steps may be used unless otherwise stated.

[0023] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0024] Any specific numerical values ​​disclosed herein (including the endpoints of numerical ranges) are not limited to their exact values, but should be understood to also include values ​​close to the exact value, such as all possible values ​​within ±5% of the exact value. Furthermore, with respect to the disclosed numerical ranges, one or more new numerical ranges can be obtained by arbitrarily combining the endpoint values ​​of the range, the endpoint values ​​with specific point values ​​within the range, and the specific point values ​​themselves; these new numerical ranges should also be considered as specifically disclosed herein.

[0025] Unless otherwise stated, the terms used herein have the same meaning as commonly understood by those skilled in the art, and if a term is defined herein and its definition differs from the common understanding in the art, the definition herein shall prevail.

[0026] The “ultrafine weakly magnetic hematite” mentioned in this article refers to hematite with a particle size D50 of 10μm to 20μm.

[0027] The term "TFe grade" as used in this article refers to the mass percentage of iron (Fe) in materials (ore, tailings, concentrate, etc.). "TFe content" and "TFe grade" are interchangeable in this article.

[0028] Unless otherwise specified, "%" in this article refers to the percentage content by mass.

[0029] For red mud tailings containing high-aluminosilicate gangue minerals (such as kaolinite, illite, nepheline, etc. with a high-aluminosilicate content greater than 55%), the gangue minerals have ultra-fine particle size and large specific surface area. The layered structure of the clay minerals leads to the aggregation of opposite charges on the edges and faces, and some minerals have water absorption and swelling properties. In addition, the slurry has a high concentration of Na+ ions. + K + Compression of the electric double layer interferes with electrostatic dispersion. These factors together make conventional dispersion methods ineffective, resulting in high consumption of conventional inorganic dispersants, high pulp viscosity, and the inability of iron-bearing minerals such as hematite and gangue minerals to separate into individual particles, thus affecting the subsequent magnetic separation effect.

[0030] For red mud tailings containing calcite as gangue minerals, the main drawback lies in the Ca²⁺ leached from the calcite. + Chemical interference with the dispersion system. Ca² + Compressing the electric double layer weakens electrostatic repulsion; if certain conventional inorganic reagents are used, calcium precipitates will be generated, leading to dispersion failure. Conventional dispersion methods also make it difficult to achieve the individual dissociation of the iron-bearing mineral hematite and gangue minerals.

[0031] For red mud tailings containing gangue minerals such as calcite and high-aluminosilicates, on the one hand, high-aluminosilicates (such as kaolinite, illite, and nepheline) have ultra-fine particle size, large specific surface area, and complex surface charge, easily forming stable 'edge-face' agglomerates, resulting in high slurry viscosity and difficulty in dispersion; on the other hand, calcite and calcium-containing aluminosilicates release Ca²⁺ into the slurry. + This process compresses the electric double layer, weakens electrostatic repulsion, and can even lead to the formation of calcium precipitates with conventional inorganic dispersants. These two factors make it more difficult for conventional dispersion methods to achieve the individual dissociation of hematite and gangue minerals.

[0032] Please see Figure 1 Some embodiments of this application provide a method for recovering ultrafine weakly magnetic hematite from Bayer process red mud magnetic separation tailings, comprising the following steps: S1 provides Bayer process red mud magnetic separation tailings with a particle size D50 of 10μm~20μm. The iron-bearing minerals include weakly magnetic hematite, and the gangue minerals contain 55%~60% aluminosilicates and 0~20% calcite. S2, mix the Bayer process red mud magnetic separation tailings with water to obtain a slurry with a mass concentration of 20%~30%; S3, An inorganic dispersant is added to the slurry and stirred to disperse it, resulting in a dispersed slurry. The inorganic dispersant includes a first dispersant and a second dispersant. The first dispersant includes sodium pyrophosphate and / or water glass, and the second dispersant includes sodium hexametaphosphate and / or sodium tripolyphosphate. The mass ratio of the first dispersant to the second dispersant is (1~3):(1~3). The amount of inorganic dispersant added is 1 kg / t to 4 kg / t based on dry tailings. S4. The dispersed slurry is subjected to high-gradient magnetic separation under a background field strength of not less than 1.5 T. The concentrate is collected as hematite rough concentrate and the tailings are collected as beneficiation tailings.

[0033] It should be noted that the above method does not add any organic reagents. Organic reagents refer to any one or more of organic collectors, foaming agents, and flocculants.

[0034] The method for recovering ultrafine weakly magnetic hematite from Bayer process red mud magnetic separation tailings in this application embodiment uses Bayer process red mud magnetic separation tailings as raw material, with a particle size D50 of 10μm~20μm. The main iron-bearing mineral component is weakly magnetic hematite, and the gangue minerals contain 55%~60% aluminosilicates and 0~20% calcite. Then, the Bayer process red mud magnetic separation tailings are prepared into a slurry with a mass concentration of 20%~30%, and 1 kg / t~4 kg / t (based on dry tailings) of a specific inorganic dispersant (including a first dispersant and a second dispersant) is added to the slurry. After dispersion, high-gradient magnetic separation is performed under a background field strength of not less than 1.5 T, thereby realizing the recovery of ultrafine (particle size D50 of 10μm~20μm) hematite. A specific inorganic dispersant (including a first dispersant and a second dispersant) of 1 kg / t to 4 kg / t (based on dry tailings) works synergistically within a specific concentration window (20% to 30% mass concentration of slurry). It can effectively disperse ultrafine mineral particles (D50 of 10 μm to 20 μm) without the addition of any organic reagents, achieving effective dispersion of solid particles in tailings with different compositions (gangue minerals containing 55% to 60% aluminosilicates and 0 to 20% calcite). At the same time, combined with high-gradient strong magnetic separation treatment under specific conditions (background field strength not less than 1.5 T), iron-bearing minerals are separated from gangue minerals, achieving efficient enrichment of weakly magnetic hematite, improving the TFe grade of hematite rough concentrate and the recovery rate of hematite. Specifically, in a slurry with a mass concentration of 20%–30%, the solid particles have a suitable interaction distance. This ensures that the inorganic dispersant can fully act on the surface of the solid particles, while also providing sufficient space for the solid particles to move and disperse fully in response to the dispersing effect of the inorganic dispersant, forming a stable dispersion system. This also provides the necessary separation fluid conditions for high-gradient magnetic separation, facilitating more uniform passage of solid particles through the separation process, thereby synergistically improving the TFe grade of hematite rough and concentrate and the recovery rate of hematite. The inorganic dispersant includes a first dispersant and a second dispersant. The first dispersant includes sodium pyrophosphate and / or water glass, and the second dispersant includes sodium hexametaphosphate and / or sodium tripolyphosphate. The first dispersant can first act on Ca²⁺. + Eliminate Ca² +The inorganic dispersant has a negative impact on the dispersion system and simultaneously provides electrostatic repulsion or steric hindrance effect on the surface of solid particles adsorbed on the Bayer process red mud magnetic separation tailings. The second dispersant can stabilize the surface of solid particles on the Bayer process red mud magnetic separation tailings, while providing steric hindrance effect or stronger electrostatic repulsion. The two work synergistically to break the heterogeneous agglomeration of iron-bearing minerals and gangue minerals at a pulp concentration of 20%~30%, achieving the individual dissociation of all solid particles in ultrafine Bayer process red mud magnetic separation tailings (particle size D50 of 10μm~20μm). Furthermore, the dual effect of electrostatic repulsion combined with steric hindrance effectively solves the dispersion attenuation problem of pulp under the dynamic conditions of high gradient strong magnetic separation, thereby improving the TFe grade of hematite rough and concentrate and the recovery rate of hematite. The dosage of inorganic dispersant is 1 kg / t~4 kg / t. kg / t can fully utilize the inorganic dispersant and solid particles in the Bayer process red mud magnetic separation tailings, thereby achieving the individual dissociation of all solid particles and improving the TFe grade of hematite rough concentrate and the recovery rate of hematite. In addition, the background field strength of not less than 1.5 T in the high gradient strong magnetic separation treatment can ensure that the magnetic medium is fully magnetized and generate a sufficiently high magnetic field gradient, which can effectively capture magnetic particles in the Bayer process red mud magnetic separation tailings with a particle size D50 of 10μm~20μm, thereby improving the TFe grade of hematite rough concentrate and the recovery rate of hematite.

[0035] In some embodiments, the inorganic dispersant is industrial grade with a purity of ≥98%.

[0036] In some implementations, the modulus of the water glass is 2.8 to 3.2.

[0037] The phrase "particle size D50 is 10μm~20μm" can be understood as the particle size D50 being 10μm, 12μm, 14μm, 16μm, 18μm, 20μm, or any value between them or any range between any two values.

[0038] The above "mass concentration of 20%~30%" can be understood as the mass concentration being 20%, 22%, 24%, 26%, 28%, 30%, or any value between them or any two values.

[0039] The above "1 kg / t ~ 4 kg / t" can be understood as the amount of inorganic dispersant added, calculated based on dry tailings, being 1 kg / t, 1.5 kg / t, 2 kg / t, 2.5 kg / t, 3 kg / t, 3.5 kg / t, 4 kg / t, and any value between them or any range between any two values.

[0040] In some embodiments, the first dispersant is water glass, and the second dispersant is sodium hexametaphosphate, with a mass ratio of water glass to sodium hexametaphosphate of (1~3):1, for example, 1:1, 2:1, or 3:1. Water glass adsorbs onto the surface of gangue minerals, providing steric hindrance, while sodium hexametaphosphate adsorbs onto the surface of gangue minerals, providing strong electrostatic repulsion. The synergistic effect of water glass and sodium hexametaphosphate at a mass ratio of (1~3):1 is more conducive to achieving efficient dispersion and monomer dissociation of the iron-bearing mineral hematite and gangue minerals, thereby further improving the TFe grade of hematite rough concentrate and the recovery rate of hematite.

[0041] Optionally, the order of adding water glass and sodium hexametaphosphate is to add water glass first and then sodium hexametaphosphate. Step S3 includes adding water glass for the first stirring and then adding sodium hexametaphosphate for the second stirring. The first stirring speed is 600 rpm to 800 rpm, and the first stirring time is 5 min to 6 min. The second stirring speed is 600 rpm to 800 rpm, and the second stirring time is 8 min to 10 min. Adding water glass first and then sodium hexametaphosphate "quickly precipitates / solidifies calcium ions, and then prevents excessive agglomeration or hardening through complexation and dispersion, thereby obtaining adjustable fluidity, stability, and coagulation characteristics." This can further enhance the dispersion effect between the iron-bearing mineral hematite and gangue minerals, and is more conducive to improving the TFe grade of hematite rough concentrate and the recovery rate of hematite. The speed and time of the first stirring, as well as the speed and time of the second stirring, are more conducive to the uniform and sufficient contact between the inorganic dispersant and the solid particles.

[0042] In some embodiments, the first dispersant is sodium pyrophosphate, and the second dispersant is sodium hexametaphosphate, with a mass ratio of sodium pyrophosphate to sodium hexametaphosphate of (1~3):3, for example, 1:3, 2:3, or 3:3. Sodium pyrophosphate molecules are small and diffuse quickly, preferentially reacting with free Ca²⁺ in the slurry. + Formation of soluble complexes, rapidly reducing Ca² + The concentration eliminates the compression effect on the double electric layer of particles, while providing electrostatic repulsion and preventing subsequent calcium precipitation, thus providing a stable environment for sodium hexametaphosphate. This allows the long-chain molecules of sodium hexametaphosphate to be firmly adsorbed onto the surface of solid particles, providing a higher density of negative charge and generating strong electrostatic repulsion. After the long-chain molecules of sodium hexametaphosphate are adsorbed on the particle surface, some chain segments extend into the solution, combining with water molecules to form a hydration layer, thereby creating an auxiliary steric hindrance effect. The synergistic effect of sodium pyrophosphate and sodium hexametaphosphate at a mass ratio of (1~3):3 is more conducive to achieving efficient dispersion and monomer dissociation of iron-bearing minerals hematite and gangue minerals, further improving the TFe grade of hematite rough concentrate and the recovery rate of hematite.

[0043] Optionally, in step S3, sodium hexametaphosphate and sodium pyrophosphate are added simultaneously, with the third stirring speed at 600 rpm to 800 rpm and the stirring time at 10 min to 15 min. The simultaneous addition of sodium hexametaphosphate and sodium pyrophosphate further enhances the dispersion effect between the iron-bearing mineral hematite and gangue minerals, which is more conducive to improving the TFe grade of hematite rough concentrate and the recovery rate of hematite. The third stirring speed and time are also more conducive to the uniform and sufficient contact between the inorganic dispersant and the solid particles.

[0044] In some embodiments, the first dispersant is water glass, and the second dispersant is sodium tripolyphosphate, with a mass ratio of water glass to sodium tripolyphosphate of 1:(0.5~1.5), for example, 1:0.5, 1:1, or 1:1.5. In this embodiment, sodium tripolyphosphate adsorbs onto the surface of gangue minerals to provide strong electrostatic repulsion, while water glass adsorbs onto the surface of gangue minerals to provide steric hindrance. The synergistic effect of sodium tripolyphosphate and water glass at a mass ratio of (0.5~1.5):1 is more conducive to achieving efficient dispersion and monomer dissociation of the iron-bearing mineral hematite and gangue minerals.

[0045] Optionally, the order of adding sodium tripolyphosphate and water glass is as follows: sodium tripolyphosphate is added first, followed by water glass. Step S3 includes adding sodium tripolyphosphate first for a fourth stirring, and then adding water glass for a fifth stirring. The fourth stirring speed is 600 rpm to 800 rpm, and the fourth stirring time is 5 min to 6 min. The fifth stirring speed is 600 rpm to 800 rpm, and the fifth stirring time is 8 min to 10 min. Adding sodium tripolyphosphate first, followed by water glass, can further enhance the dispersion effect between the iron-bearing mineral hematite and gangue minerals, which is more conducive to improving the TFe grade of hematite rough concentrate and the recovery rate of hematite. The speed and time of the fourth stirring, as well as the speed and time of the fifth stirring, are all more conducive to the uniform and sufficient contact between the inorganic dispersant and the solid particles.

[0046] In some implementations, high-gradient magnetic separation employs a process of one roughing and two scavenging stages. The background field strength for the roughing stage is 1.5 T to 1.6 T, for the first scavenging stage it is 1.7 T to 1.8 T, and for the second scavenging stage it is 1.6 T to 1.7 T. This high-gradient magnetic separation process provides better magnetic separation performance, further improving the TFe grade in hematite concentrate and the recovery rate of hematite.

[0047] In some implementations, the high gradient magnetic separation process employs a vertical ring high gradient magnetic separator, in which the magnetic separation medium is stainless steel wool with a diameter of 0.1 mm to 0.2 mm, and the filling rate of the stainless steel wool is 8% to 12%.

[0048] In some embodiments, the slurry flow rate for high-gradient magnetic separation is 0.8 m / min to 1.2 m / min, and may also be 0.9 m / min, 1.0 m / min, or 1.1 m / min. Within this range, the slurry flow rate can further improve the TFe grade of hematite roughing concentrate and the recovery rate of hematite.

[0049] In some implementations, the magnetic separation temperature for high gradient magnetic separation is 20°C to 25°C.

[0050] In some implementations, such as Figure 2 As shown, the above method further includes step S5, adjusting the pH of the beneficiation tailings to 10-12 using a pH adjuster, and controlling the residual amount of inorganic dispersant in the beneficiation tailings to ≤60mg / L before sending it to the settling process of Bayer process alumina production. After pH adjustment and control of the residual amount of inorganic dispersant, the beneficiation tailings can be directly returned to the Bayer process alumina production, realizing the recycling of red mud tailings.

[0051] Optionally, the pH adjuster is waste alkaline solution generated during the Bayer process for alumina production. Using waste alkaline solution allows for further comprehensive resource utilization.

[0052] In some implementations, such as Figure 3 As shown, the above method further includes step S6, which involves subjecting the hematite rough concentrate to a fine magnetic treatment to obtain hematite concentrate. Optionally, the background field strength of the fine magnetic treatment is 1.4T~1.5T, and the fine magnetic treatment time is 3 min~5 min.

[0053] In some embodiments, the TFe grade of the Bayer process red mud magnetic separation tailings is less than 35%, and can be selected as 32% to 35%. The method provided in this application also has a great dispersing effect on Bayer process red mud magnetic separation tailings with a TFe grade of less than 35% and can effectively recover the ultrafine weak magnetic hematite (particle size D50 of 10μm to 20μm).

[0054] In some implementations, Bayer red mud magnetic separation tailings can be obtained from Bayer red mud through conventional magnetic separation processes.

[0055] In some embodiments, the tailings from the Bayer process red mud magnetic separation can be further obtained through a pretreatment step, which may include dispersing and slurrying the tailings obtained by conventional magnetic separation, and then removing coarse particulate impurities with a particle size greater than 0.1 mm from the slurry after stirring evenly.

[0056] Example To better understand this application, the following description, in conjunction with embodiments, further illustrates this application. However, the scope of protection claimed in this application is not limited to the scope of the embodiments.

[0057] In the following examples, unless otherwise specified, all experimental instruments, raw materials, and quantities involved are commercially available products or can be prepared by known methods. Experimental methods not specifying particular conditions in the examples were performed under conventional conditions, such as those described in literature, books, or methods recommended by the manufacturer.

[0058] Unless otherwise specified, the specific parameters used in each step of the preparation process of the materials in each embodiment and comparative example are the same.

[0059] Example 1 S1, Bayer process red mud magnetic separation tailings: TFe content 33%, the main iron-bearing mineral is ultrafine weak magnetic hematite, gangue minerals include 60% aluminosilicate and 10% calcite, pH is 11.2.

[0060] The Bayer process red mud magnetic separation tailings were fed into a disperser and dispersed. Water was added to adjust the slurry concentration to 25%. The slurry was stirred at 600 rpm for 6 minutes. Coarse particles larger than 0.1 mm were removed by hydraulic classification. After drying, Bayer process red mud magnetic separation tailings with a D50 of 15 μm were obtained.

[0061] S2, Bayer red mud magnetic separation tailings with a D50 of 15μm are mixed with water to prepare a slurry with a mass concentration of 25%.

[0062] S3. Add an inorganic dispersant to the above slurry and stir to disperse it. The inorganic dispersant includes sodium hexametaphosphate and water glass, with a total dosage of 2.4 kg / t, of which sodium hexametaphosphate is 0.8 kg / t and water glass is 1.6 kg / t. The mass ratio of sodium hexametaphosphate to water glass is 1:2. First add water glass and stir for 5 min, then add sodium hexametaphosphate and continue stirring for 10 min at a speed of 650 rpm.

[0063] S4. The dispersed slurry is fed into a vertical ring high gradient magnetic separator. The magnetic separation medium is stainless steel wool with a diameter of 0.15 mm and a filling rate of 10%. The process consists of one roughing and two scavenging: the background field strength of the roughing is 1.55 T and the magnetic separation flow rate is 1.0 m / min, and the roughing concentrate is collected; the background field strength of the first scavenging is 1.75 T and the magnetic separation flow rate is 0.9 m / min, and the first scavenging concentrate is collected; the background field strength of the second scavenging is 1.65 T and the magnetic separation flow rate is 1.1 m / min, and the second scavenging concentrate is collected; the three concentrates are combined to obtain hematite rough concentrate; the three tailings are combined to obtain the beneficiation tailings.

[0064] S5, the pH of the tailings after selection is adjusted to 11.5 using Bayer process waste alkaline solution, and the residual sodium hexametaphosphate is tested to be 42 mg / L, and then directly sent to the sedimentation process of Bayer process alumina production.

[0065] Example 2 S1 is prepared in a manner that is basically the same as that in Example 1, except that the mass percentage of calcite in the gangue minerals of the Bayer process red mud magnetic separation tailings is 20%.

[0066] S2, Bayer red mud magnetic separation tailings with a D50 of 15μm are mixed with water to prepare a slurry with a mass concentration of 25%.

[0067] S3. Add an inorganic dispersant to the above slurry and stir to disperse it. The inorganic dispersant includes sodium hexametaphosphate and sodium pyrophosphate, with a total dosage of 2.0 kg / t, of which sodium hexametaphosphate is 1.2 kg / t and sodium pyrophosphate is 0.8 kg / t. The mass ratio of sodium hexametaphosphate to sodium pyrophosphate is 3:2. Sodium hexametaphosphate and sodium pyrophosphate are added at the same time and stirred for 12 min at a speed of 750 rpm.

[0068] S4, same as Example 1.

[0069] S5. The pH of the tailings after selection is adjusted to 11.5 using Bayer process waste alkali solution. The residual sodium hexametaphosphate is tested and found to be 40 mg / L. The tailings are then directly sent to the sedimentation process of Bayer process alumina production.

[0070] Example 3 S1 is prepared in a manner similar to that of Example 1, except that the TFe content in the Bayer process red mud magnetic separation tailings is 30%, the D50 is 10 μm, and the pH is 10.8.

[0071] S2, Bayer red mud magnetic separation tailings with a D50 of 10μm are mixed with water to prepare a slurry with a mass concentration of 20%.

[0072] S3. Add an inorganic dispersant to the above slurry and stir to disperse it. The inorganic dispersant includes sodium tripolyphosphate and water glass, with a total dosage of 3.0 kg / t, of which sodium tripolyphosphate is 1.5 kg / t and water glass is 1.5 kg / t. The mass ratio of sodium tripolyphosphate to water glass is 1:1. First add sodium tripolyphosphate and stir for 6 min, then add water glass and stir for 8 min at a speed of 600 rpm.

[0073] S4. The dispersed slurry is fed into a vertical ring high gradient magnetic separator. The magnetic separation medium is stainless steel wool with a diameter of 0.1 mm and a filling rate of 8%. The process consists of one roughing and two scavenging: the background field strength of the roughing is 1.5T and the magnetic separation flow rate is 0.8 m / min, and the roughing concentrate is collected; the background field strength of the first scavenging is 1.7T and the magnetic separation flow rate is 0.8 m / min, and the first scavenging concentrate is collected; the background field strength of the second scavenging is 1.6T and the magnetic separation flow rate is 1.0 m / min, and the second scavenging concentrate is collected; the three concentrates are combined to obtain hematite rough concentrate; the three tailings are combined to obtain the beneficiation tailings.

[0074] S5. The pH of the tailings after selection is adjusted to 10.8 using Bayer process waste alkali solution. The residual sodium hexametaphosphate is tested and found to be 53 mg / L. The tailings are then directly sent to the sedimentation process of Bayer process alumina production.

[0075] Example 4 S1 is prepared in a manner similar to that of Example 1, except that the TFe content in the Bayer process red mud magnetic separation tailings is 32%, the gangue minerals include 55% aluminosilicates and 18% calcite, the D50 is 14 μm, and the pH is 11.1.

[0076] S2, Bayer red mud magnetic separation tailings with a D50 of 14μm are mixed with water to prepare a slurry with a mass concentration of 24%.

[0077] S3. Add an inorganic dispersant to the above slurry and stir to disperse it. The inorganic dispersant includes sodium hexametaphosphate and sodium pyrophosphate, with a total dosage of 2.2 kg / t, of which sodium hexametaphosphate is 1.32 kg / t and sodium pyrophosphate is 0.88 kg / t. The mass ratio of sodium hexametaphosphate to sodium pyrophosphate is 3:2. Sodium hexametaphosphate and sodium pyrophosphate are added at the same time and stirred for 12 min at a speed of 720 rpm.

[0078] S4. The dispersed slurry is fed into a vertical ring high gradient magnetic separator. The magnetic separation medium is stainless steel wool with a diameter of 0.15 mm and a filling rate of 10%. The process consists of one roughing and two scavenging: the background field strength of the roughing is 1.55 T and the magnetic separation flow rate is 0.95 m / min, and the roughing concentrate is collected; the background field strength of the first scavenging is 1.75 T and the magnetic separation flow rate is 0.85 m / min, and the first scavenging concentrate is collected; the background field strength of the second scavenging is 1.65 T and the magnetic separation flow rate is 1.05 m / min, and the second scavenging concentrate is collected; the three concentrates are combined to obtain hematite rough concentrate; the three tailings are combined to obtain the beneficiation tailings.

[0079] S5. The pH of the tailings after selection is adjusted to 10.8 using Bayer process waste alkali solution. The residual sodium hexametaphosphate is tested and found to be 53 mg / L. The tailings are then directly sent to the sedimentation process of Bayer process alumina production.

[0080] S6, the hematite rough concentrate is refined by a field strength of 1.45T and a refining time of 4min to obtain hematite concentrate.

[0081] Comparative Example 1 (Single agent: Sodium hexametaphosphate) It is basically the same as Example 1, except that the inorganic dispersant consists of only 2.4 kg / t of sodium hexametaphosphate.

[0082] Comparative Example 2 It is basically the same as Example 1, except that the inorganic dispersant consists of only 2.4 kg / t of sodium hexametaphosphate.

[0083] Comparative Example 2 (Single Agent: Sodium Pyrophosphate) It is basically the same as Example 2, except that the inorganic dispersant consists of only 2.0 kg / t of sodium pyrophosphate.

[0084] Comparative Example 3 (Single Agent: Water Glass) It is basically the same as Example 3, except that the inorganic dispersant is only 3.0 kg / t of water glass.

[0085] Comparative Example 4 (Single Agent: Sodium Tripolyphosphate) It is basically the same as Example 3, except that the inorganic dispersant is only 3.0 kg / t sodium tripolyphosphate.

[0086] Test case The TFe grade of hematite rough and concentrate, the TFe grade of hematite concentrate, and the recovery rate of hematite were tested, and the test results are listed in Table 1: Table 1

[0087] The above comparison shows that the method for recovering ultrafine weakly magnetic hematite from Bayer process red mud magnetic separation tailings provided in this application has a higher TFe grade in the hematite concentrate and a higher hematite recovery rate.

[0088] Compared with existing technologies, the method for recovering ultrafine weakly magnetic hematite from Bayer process red mud magnetic separation tailings provided in this application has at least the following beneficial effects: No organic pollution: No organic agents (collectors, foaming agents, flocculants, etc.) are added throughout the process, completely avoiding the toxicity of organic agents to the Bayer process alumina main process. The tailings after beneficiation can be directly returned to the Bayer process production process, achieving process compatibility and solving the pain points of industrial implementation.

[0089] Wide dispersion adaptability: Through the selection and synergistic design of multiple inorganic dispersants, it is suitable for Bayer process red mud magnetic separation tailings with different compositions such as aluminosilicate type, calcium-magnesium type, and ultrafine particle type, achieving precise dispersion and solving the industry problem of poor adaptability of single dispersants.

[0090] High recovery efficiency: Through the synergistic effect of "adsorption-chelation-stabilization", the compound reagent further improves the dispersion effect of ultrafine weak magnetic hematite while reducing the total amount of reagent used. The TFe grade of the concentrate can reach 51-57%, and the hematite recovery rate can reach 63-79%, which is 3-5 percentage points higher than that of the single reagent.

[0091] The process is simple and energy-saving: the process is short and easy to operate. It uses room temperature magnetic separation and does not require roasting or complex flotation equipment. The dispersants used are all commonly used industrial inorganic reagents, which are easy to obtain, cost-controllable, and easy to promote on a large scale.

[0092] Environmentally friendly and energy-saving: It realizes the recycling of red mud tailings, reduces stockpiling pollution, and the dispersant is an inorganic component, which does not cause secondary pollution, and meets the policy requirements for green mine construction and comprehensive resource utilization.

[0093] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

[0094] Although preferred embodiments have been described in this specification, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this specification.

[0095] Obviously, those skilled in the art can make various modifications and variations to this specification without departing from its spirit and scope. Therefore, if such modifications and variations fall within the scope of the claims and their equivalents, this specification is also intended to include such modifications and variations.

Claims

1. A method for recovering ultrafine weakly magnetic hematite from Bayer process red mud magnetic separation tailings, characterized in that, Includes the following steps: Provide Bayer process red mud magnetic separation tailings, wherein the particle size D50 of the Bayer process red mud magnetic separation tailings is 10μm~20μm, and the iron-containing minerals in the Bayer process red mud magnetic separation tailings include weakly magnetic hematite, and the gangue minerals include 55%~60% aluminosilicates and 0~20% calcite. The tailings from the Bayer process red mud magnetic separation were mixed with water to obtain a slurry with a mass concentration of 20% to 30%. An inorganic dispersant is added to the slurry and stirred to disperse it, resulting in a dispersed slurry. The inorganic dispersant includes a first dispersant and a second dispersant. The first dispersant includes sodium pyrophosphate and / or water glass, and the second dispersant includes sodium hexametaphosphate and / or sodium tripolyphosphate. The mass ratio of the first dispersant to the second dispersant is (1~3):(1~3). The amount of the inorganic dispersant added is 1 kg / t to 4 kg / t based on dry tailings. The dispersed slurry is subjected to high-gradient magnetic separation under a background field strength of not less than 1.5 T. The concentrate is collected as hematite rough concentrate, and the tailings are collected as beneficiation tailings.

2. The method according to claim 1, characterized in that, The first dispersant is water glass, and the second dispersant is sodium hexametaphosphate, wherein the mass ratio of the water glass to the sodium hexametaphosphate is (1~3):1; and / or, The step of adding an inorganic dispersant to the slurry for stirring and dispersion includes first adding water glass for first stirring, and then adding sodium hexametaphosphate for second stirring. The first stirring speed is 600 rpm to 800 rpm and the first stirring time is 5 min to 6 min. The second stirring speed is 600 rpm to 800 rpm and the second stirring time is 8 min to 10 min.

3. The method according to claim 1, characterized in that, The first dispersant is sodium pyrophosphate, and the second dispersant is sodium hexametaphosphate, wherein the mass ratio of sodium pyrophosphate to sodium hexametaphosphate is (1~3):3; and / or, In the step of adding an inorganic dispersant to the slurry and stirring to disperse it, sodium pyrophosphate and sodium hexametaphosphate are added simultaneously. The stirring time is 10 min to 15 min, and the stirring speed is 600 rpm to 800 rpm.

4. The method according to claim 2, characterized in that, The first dispersant is water glass, and the second dispersant is sodium tripolyphosphate, wherein the mass ratio of the water glass to the sodium tripolyphosphate is 1:(0.5~1.5); and / or, The step of adding an inorganic dispersant to the slurry and stirring to disperse it includes first adding sodium tripolyphosphate for a third stirring, and then adding water glass for a fourth stirring. The third stirring speed is 600 rpm to 800 rpm and the third stirring time is 5 min to 6 min. The fourth stirring speed is 600 rpm to 800 rpm and the fourth stirring time is 8 min to 10 min.

5. The method according to claim 1, characterized in that, The high gradient magnetic separation process includes a first coarse separation, a first sweep separation, and a second sweep separation. The background field strength of the first coarse separation is 1.5 T ~ 1.6 T, the background field strength of the first sweep separation is 1.7 T ~ 1.8 T, and the background field strength of the second sweep separation is 1.6 T ~ 1.7 T.

6. The method according to claim 1, characterized in that, The magnetic separation equipment for the high gradient magnetic separation process is a vertical ring high gradient magnetic separator. The magnetic separation medium in the vertical ring high gradient magnetic separator is stainless steel wool with a diameter of 0.1 mm to 0.2 mm, and the filling rate of the stainless steel wool is 8% to 12%.

7. The method according to claim 1, characterized in that, The slurry flow rate for the high-gradient magnetic separation treatment is 0.8 m / min ~ 1.2 m / min; and / or, The magnetic separation temperature for the high gradient magnetic separation process is 20℃~25℃.

8. The method according to any one of claims 1 to 7, characterized in that, After the steps of performing high-gradient magnetic separation on the dispersed slurry under a background field strength of not less than 1.5 T, collecting the concentrate as hematite rough concentrate and collecting the tailings as beneficiation tailings, the process further includes: adjusting the pH of the beneficiation tailings to 10-12 using a pH adjuster, and controlling the residual amount of the inorganic dispersant in the beneficiation tailings to ≤60mg / L before sending it to the sedimentation process of Bayer process alumina production.

9. The method according to claim 8, characterized in that, The pH adjuster is waste alkaline solution generated during the Bayer process of alumina production.

10. The method according to any one of claims 1 to 7, characterized in that, After the step of performing high-gradient magnetic separation on the dispersed slurry under a background field strength of not less than 1.5 T to collect the concentrate as hematite rough concentrate and the tailings as beneficiation tailings, the method further includes: performing fine magnetic separation on the hematite rough concentrate to obtain hematite concentrate; wherein the background field strength of the fine magnetic separation is 1.4T~1.5T and the time of the fine magnetic separation is 3 min~5 min.

Images