Method for upgrading bauxite after bauxite mother liquor grinding

Abstract

This application provides a method for upgrading bauxite after grinding with mother liquor, belonging to the field of mineral processing. The method includes: grinding a mixed slurry of bauxite to be upgraded and circulating mother liquor to obtain an alkaline slurry with fully liberated aluminum and gangue minerals; using the circulating mother liquor as both a separation and auxiliary medium throughout the process, performing mineral processing and upgrading on the alkaline slurry to separate iron and silicon impurities in the circulating mother liquor medium, obtaining a concentrate slurry and a tailings slurry; sending the concentrate slurry to an alumina leaching process; and separating the tailings slurry to obtain circulating mother liquor and tailings byproducts. This application, through systematic process reengineering and closed-loop media design, successfully develops a bauxite pretreatment method that can be deeply coupled and seamlessly integrated with the Bayer process main process, avoiding interference from external media, and achieving efficient impurity removal under fully liberated mineral conditions.

Description

Technical Field

[0001] This application relates to the field of mineral processing technology, and in particular to a method for upgrading bauxite mother liquor after grinding. Background Technology

[0002] Bauxite is the core raw material for alumina production, and its quality (purity, impurity content, and aluminum-silicon ratio) directly determines the technical and economic indicators of the Bayer process. With the depletion of high-quality alumina resources, existing bauxite generally faces the need for quality improvement: low-grade bauxite (Al2O3 30%–45%) suffers from a low aluminum-silicon ratio and excessive levels of impurities such as iron and silicon; medium / high-grade bauxite (Al2O3 45%–60%) may be accompanied by excessive levels of single impurities (such as iron or titanium), affecting leaching efficiency. These impurity minerals (such as Fe2O3 and SiO2) bring a series of serious problems during the Bayer process: silicon minerals react to consume alkali and form red mud, causing irreversible losses of alumina and alkali; iron minerals increase the amount of red mud, exacerbating liquid loss and potentially encapsulating aluminum minerals, hindering leaching and reducing alumina leaching efficiency.

[0003] To reduce impurities in ore, existing technologies typically include a separate pre-concentration process outside the Bayer process main flow, aiming to improve ore grade. Current mainstream pre-treatment technologies include magnetic separation for high-iron ores and flotation (or reverse flotation) for low-alumina-silica ores. However, when these traditional pre-treatment processes are integrated into the Bayer process system, they generally suffer from the following problems: process fragmentation and media incompatibility: Traditional pre-concentration is mostly conducted in aqueous media or low-alkalinity recycled water, which has significantly different physicochemical properties from the high-temperature, high-alkalinity circulating mother liquor system of the Bayer process main flow. This results in the pre-concentration system and the main process becoming two relatively independent units, making integration difficult. The introduction of external media disrupts system balance: A large amount of fresh water or recycled water used in pre-concentration enters the Bayer process system along with water other than concentrate. To evaporate this water to maintain the dissolution concentration, a large amount of steam is required, significantly increasing production costs and potentially disrupting the system's water and heat balance. The process flow is lengthy and complex: independent pre-selection systems require a series of supporting equipment for grinding, sorting, concentrate dewatering, tailings treatment, and wastewater treatment. This results in large investments, high energy consumption, numerous operational steps, and complex management. Furthermore, after concentrate dewatering, it needs to be re-mixed and homogenized with circulating mother liquor before entering the leaching process, leading to low overall process efficiency. Therefore, developing a bauxite pretreatment method that can be deeply coupled and seamlessly integrated with the Bayer process, avoiding interference from external media, and achieving efficient impurity removal under fully liberated mineral conditions is an urgent need to overcome current industry bottlenecks and realize the large-scale economic utilization of low-quality bauxite resources. Summary of the Invention

[0004] This application provides a method for upgrading bauxite mother liquor after grinding, in order to develop a bauxite pretreatment method that can be deeply coupled and seamlessly connected with the Bayer process main process, avoid interference from external media, and achieve efficient impurity removal in a fully liberated mineral state.

[0005] This application provides a method for upgrading bauxite mother liquor after grinding, the method comprising: The mixed slurry of bauxite to be upgraded and the circulating mother liquor is ground to obtain an alkaline slurry in which the aluminum minerals and gangue minerals are fully liberated; the circulating mother liquor is a caustic alkali circulating liquid produced in the alumina leaching process. The entire process uses the circulating mother liquor as the sorting and auxiliary medium to perform mineral processing and upgrading on the alkaline slurry, so as to separate iron and silicon impurities in the circulating mother liquor medium to obtain concentrate slurry and tailings slurry. The concentrate slurry is fed into the alumina leaching process; The tailings slurry is separated to obtain the circulating mother liquor and tailings by-products.

[0006] Optionally, in the bauxite to be upgraded, the content of Al2O3 is 40% to 60% by mass fraction, the content of gangue minerals is 10% to 35%, the content of SiO2 is 40% to 24%, and the content of Fe2O3 is 1.5% to 31.5%.

[0007] Optionally, the solids content of the alkaline slurry is 200 g / L to 400 g / L, and the grinding fineness of the alkaline slurry is 70% to 95% of that of -200 mesh.

[0008] Optionally, the temperature of the circulating mother liquor is 50℃~80℃, and the alkaline concentration of the circulating mother liquor, calculated as NaOH, is 150g / L~300g / L.

[0009] Optionally, the mineral processing and upgrading process includes at least one of magnetic separation, flotation, and gravity separation.

[0010] Optionally, the magnetic separation process employs a vertical ring high-gradient magnetic separator or a pulsed high-gradient magnetic separator; The flotation process employs a mechanically agitated flotation machine or an aerated agitated flotation machine. The reselection process employs a shaking table or a spiral chute.

[0011] Optionally, in the mineral processing and upgrading process, the parts of the equipment that come into contact with the slurry or circulating mother liquor are made of alkali-resistant, high-temperature-resistant, and corrosion-resistant materials, which are selected from titanium and titanium alloys, super austenitic stainless steel, or special ceramics.

[0012] Optionally, the yield of the concentrate product corresponding to the concentrate slurry is 72% to 92%, and the content of Al2O3 in the concentrate product is 46.5% to 62.5% by mass fraction, the content of SiO2 is 4.5% to 12%, and the content of Fe2O3 is 1.5% to 22.5%.

[0013] Optionally, the yield of the tailings by-product is 8.5% to 27.5%.

[0014] Optionally, the tailings by-products include iron concentrate and silicon concentrate.

[0015] The technical solutions provided in this application have the following advantages compared with the prior art: This application provides a method for upgrading bauxite mother liquor after grinding. Through systematic process reconstruction and media closed-loop design, a bauxite pretreatment method that can be deeply coupled and seamlessly connected with the Bayer process main process, avoids interference from external media, and achieves efficient impurity removal in a fully liberated mineral state has been successfully developed.

[0016] This application precisely positions the mineral processing and upgrading process after grinding and before alumina leaching, breaking the traditional pattern of independent pre-processing systems and the Bayer process main flow. By embedding the upgrading step between the inherent processes of the Bayer process, grinding, upgrading, and leaching form a continuous, straight-through process. This layout ensures that the fully dissociated slurry after grinding can directly enter the mineral processing operation without intermediate transfer, and the upgraded concentrate slurry can be directly sent to the leaching process without dewatering and conditioning. This achieves direct material flow and parameter matching between the preceding and following processes, and at the process architecture level, achieves deep coupling and seamless connection with the Bayer process main flow.

[0017] This application uses the caustic alkali circulating liquid generated from the alumina leaching process as the sole liquid medium throughout the entire process. This circulating mother liquor is used as the separation medium and auxiliary medium in both grinding and beneficiation upgrading. This design ensures that the entire pretreatment process is completed within the Bayer process's own high-temperature, high-alkali medium system, eliminating interference from external media caused by the introduction of clean water or recycled water in traditional processes. Since the beneficiation medium and the subsequent leaching medium are circulating mother liquors of the same origin and composition, the upgraded concentrate slurry is completely consistent with the requirements of the leaching process in terms of temperature, alkalinity, and chemical composition, eliminating water balance disturbances and additional steam consumption problems caused by medium switching.

[0018] This application achieves complete liberation of aluminum minerals from gangue minerals such as iron and silicon during the grinding stage, laying the foundation for subsequent efficient separation. During grinding, the bauxite and circulating mother liquor work together to completely liberate valuable and impurity minerals from the intergrowth, exposing fresh mineral surfaces. Subsequently, in the beneficiation and upgrading stage, the fully liberated minerals are precisely separated in the circulating mother liquor medium using processes such as magnetic separation, flotation, or gravity separation, enabling efficient removal of iron and silicon impurities. This process logic of liberation before separation avoids the low separation efficiency caused by insufficient mineral liberation in traditional pre-grinding selection, ensuring efficient removal of impurities and effective recovery of aluminum minerals.

[0019] This application separates and treats tailings slurry generated from mineral processing, recovering the entrained circulating mother liquor and returning it to the front end of the process for recycling, forming a closed-loop alkali solution circulation system and eliminating wastewater discharge. The separated tailings byproducts, due to separation in the circulating mother liquor medium, have low alkali content and relatively concentrated minerals, and can be directly utilized as resource products such as iron concentrate and silicon concentrate. This design not only achieves internal recycling of the medium but also reduces the total amount of impurities entering the leaching process from the source, lowering red mud production and alkali consumption, giving the entire pretreatment method the dual advantages of high-efficiency impurity removal and environmental friendliness. Attached Figure Description

[0020] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0021] 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.

[0022] Figure 1 A schematic flow diagram of a method for upgrading bauxite mother liquor after grinding, provided for an embodiment of this application; Figure 2 This is a schematic diagram illustrating the process principle of a method for upgrading bauxite mother liquor after grinding, as provided in an embodiment of this application. Detailed Implementation

[0023] 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.

[0024] The range descriptions used herein, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1 to 6" cover all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "including" and "contains" as used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship; "and / or" indicates that multiple situations can exist individually or simultaneously; expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships mentioned herein, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained through commercial purchase or prepared using existing methods.

[0025] Figure 1 A schematic flow diagram of a method for upgrading bauxite mother liquor after grinding, provided for an embodiment of this application; Figure 2 This is a schematic diagram illustrating the process principle of a method for upgrading bauxite mother liquor after grinding, as provided in an embodiment of this application.

[0026] like Figure 1 and Figure 2 As shown in the embodiment of this application, a method for upgrading bauxite mother liquor after grinding is provided, the method comprising: S1. Grind the mixed slurry of bauxite to be upgraded and the circulating mother liquor to obtain an alkaline slurry in which the aluminum minerals and gangue minerals are fully liberated; the circulating mother liquor is a caustic alkali circulating liquid produced in the alumina leaching process. S2. The entire process uses the circulating mother liquor as the separation medium and auxiliary medium to carry out mineral processing and upgrading of alkaline slurry, so as to separate iron and silicon impurities in the circulating mother liquor medium to obtain concentrate slurry and tailings slurry. S3. The concentrate slurry is fed into the alumina leaching process. S4. Separate the tailings slurry to obtain circulating mother liquor and tailings by-products.

[0027] It should be noted that S1 is the grinding and media matching step, whose core function is to achieve sufficient mineral liberation and provide qualified feed conditions for subsequent separation. Specifically, the bauxite to be upgraded is mixed with the circulating mother liquor from the alumina leaching process and then ground. This effectively breaks the symbiotic relationship between aluminum minerals and gangue minerals such as iron and silicon in an alkaline medium, allowing them to achieve a state of full liberation, which is a prerequisite for ensuring the efficiency of subsequent separation. In this step, the circulating mother liquor serves a dual role as both the grinding medium and the subsequent reaction medium. Its temperature is controlled at 50–80℃, and the alkali concentration (calculated as NaOH) is 150–300 g / L. These parameter settings ensure that the slurry system is highly consistent with the subsequent leaching process. The grinding operation requires adjusting the slurry solids content to 200–400 g / L and controlling the grinding fineness within the range of 70%–95% of -200 mesh. This parameter range can create favorable particle size conditions for subsequent separation operations while ensuring sufficient mineral liberation.

[0028] S2 is the mineral processing and upgrading step, which utilizes the differences in physical or physicochemical properties between bauxite and impurity minerals to achieve efficient separation in a circulating mother liquor medium. The key innovation of this step is the use of the same circulating mother liquor as the grinding step as the sole separation and auxiliary medium throughout the process, without introducing any liquid media outside the Bayer process, thus maintaining the consistency of the system medium. Depending on the main impurity types in the bauxite, the mineral processing and upgrading step can be flexibly configured with at least one of magnetic separation, flotation, or gravity separation processes. When processing high-iron bauxite, a vertical ring or pulsed high-gradient magnetic separator is used to capture and separate magnetic iron minerals under the action of a magnetic field; when processing high-silica, low-grade bauxite, a mechanically agitated or aerated flotation machine is used, in conjunction with alkali-resistant collectors and frothers, to remove silica minerals through flotation; when processing ores with significant density differences, shaking tables or spiral sluices can be used for gravity separation. To ensure the long-term stable operation of the equipment in a high-temperature and highly alkaline environment, all parts in contact with the slurry are made of alkali-resistant, high-temperature-resistant, and corrosion-resistant materials such as titanium and titanium alloys, super austenitic stainless steel, or special ceramics.

[0029] S3 is the direct leaching step of the concentrate slurry. The concentrate slurry obtained after beneficiation and upgrading still uses the circulating mother liquor as its liquid phase medium, while the solid phase consists of enriched aluminum minerals. Since the temperature, alkalinity, and solids content of the concentrate slurry naturally match the requirements of subsequent leaching processes, it can be directly fed into the alumina leaching process without the need for intermediate steps such as dehydration, drying, or re-mixing. This direct-flow process design simplifies the production process to the greatest extent possible, avoiding energy losses and equipment investment caused by material transfer and medium conversion.

[0030] S4 is the tailings separation and media recovery step, aimed at achieving media recycling and by-product resource utilization. The tailings slurry produced during mineral processing and upgrading carries some circulating mother liquor, which needs to be separated from the solid tailings through sedimentation concentration and / or filtration and washing. The recovered circulating mother liquor is returned to steps S1 and S2 for recycling, achieving a closed-loop circulation of the alkali solution and eliminating wastewater discharge. The solid tailings by-products obtained after separation can be used to obtain high-grade iron concentrate (Fe2O3 content greater than 65%) or silica-rich tailings, depending on the type of raw ore and the separation process. These can be used as raw materials for iron smelting or for other industrial applications, achieving comprehensive utilization of associated resources.

[0031] In some embodiments, the bauxite to be upgraded contains, by mass fraction, 40%–60% Al2O3, 10%–35% gangue minerals, 40%–24% SiO2, and 1.5%–31.5% Fe2O3.

[0032] In some embodiments, the solids content of the alkaline slurry is 200 g / L to 400 g / L, and the grinding fineness of the alkaline slurry is -200 mesh, accounting for 70% to 95%.

[0033] Solids content in ore pulp is a key process parameter in the leaching process, directly affecting upgrading efficiency, process economy, process efficiency, and process stability. Excessive solids content leads to excessive pulp viscosity, hindering the action of the separation media (e.g., flotation bubbles cannot disperse, magnetic particles are difficult to capture, and gravity separation minerals are difficult to separate). Insufficient solids content results in insufficient mineral particle concentration per unit volume, low probability of impurities colliding with the separation media (magnetic field / bubble / gravity), difficulty in effectively separating impurities such as iron and silicon, decreased separation efficiency, reduced equipment ore processing capacity, and a significant increase in energy consumption per unit capacity, leading to a significant increase in production costs. Examples of suitable solids contents for ore pulp include 200, 250, 300, 350, and 400 g / L.

[0034] Grinding fineness is a core prerequisite for effective ore upgrading. Before separation, it is essential to ensure sufficient dissociation of aluminum minerals from impurities such as iron and silicon to prevent intergrowths from causing separation failure. If the grinding fineness is too low, aluminum minerals and impurities will not be fully dissociated, and intergrowths cannot be captured by the separation medium. The upgraded ore will not meet leaching requirements, and undissociated impurities will enter the leaching process with the slurry, increasing alkali consumption and red mud volume. If the grinding fineness is too high, grinding energy consumption increases, requiring more electricity for finer grinding, accelerating wear on steel balls and liners, and significantly raising production costs. Simultaneously, ultrafine aluminum minerals are easily carried into the tailings by impurities, leading to a decrease in alumina recovery rate. For example, the fineness of the slurry after grinding may be 70%, 75%, 80%, 85%, 90%, or 95% of the material at -200 mesh.

[0035] In some embodiments, the temperature of the circulating mother liquor is 50°C to 80°C, and the alkaline concentration of the circulating mother liquor, calculated as NaOH, is 150 g / L to 300 g / L.

[0036] Controlling the temperature of the circulating mother liquor is crucial to maintaining consistency with the temperature of subsequent leaching processes, eliminating the need for additional heating, reducing steam consumption, and maintaining system thermal balance. Excessively low temperatures lead to increased slurry viscosity, hindered magnetic particle movement, easy merging of flotation bubbles, and slow gravity separation stratification, all of which negatively impact separation efficiency. Furthermore, excessively large temperature differences with the leaching process necessitate additional steam heating of the slurry, increasing steam consumption. Conversely, excessively high temperatures create a highly alkaline environment that exacerbates the wear and tear on alkali-resistant materials such as titanium alloys and special ceramics, shortening equipment lifespan, increasing maintenance costs, and altering the physical properties of the slurry, thus affecting separation performance. For example, the temperature of the circulating mother liquor can be 50℃, 60℃, 65℃, 70℃, or 80℃.

[0037] Controlling the alkalinity of the circulating mother liquor is primarily to match the caustic alkali concentration in the leaching process. After upgrading, the slurry requires no additional alkali or dilution and can be directly leached, avoiding fluctuations in alkali concentration that could affect reaction stability. For example, the alkalinity of the circulating mother liquor can be 150, 200, 250, or 300 g / L.

[0038] In some implementations, the mineral processing and upgrading process includes at least one of magnetic separation, flotation, and gravity separation.

[0039] The reason for adopting different upgrading processes is to accurately match the upgrading needs of different ore types and different types of impurity minerals, and to achieve targeted impurity removal.

[0040] Magnetic separation is based on the magnetic difference between aluminum minerals (non-magnetic) and iron-based impurity minerals (strongly magnetic / weakly magnetic). Under the action of a magnetic field, magnetic iron minerals are adsorbed and separated by magnetic separation equipment, while non-magnetic aluminum minerals flow out with the slurry, thus achieving iron removal and quality improvement. It is suitable for separating Fe2O3 minerals such as hematite, magnetite, and limonite, as well as magnetic impurities with magnetic response in iron-aluminum intergrowths.

[0041] The flotation process uses alkali-resistant flotation reagents (collector + depressant) to regulate the difference in hydrophobicity of mineral surfaces, so that the target impurity minerals (silicon-based) adsorb the collector and become hydrophobic, attaching to bubbles and floating to separate. Aluminum minerals are inhibited by the depressant and remain in the pulp, thus achieving desilication and quality improvement. It is suitable for removing SiO2-type mineral impurities such as kaolinite, illite, and pyrophyllite.

[0042] Gravity separation is based on the density difference between aluminum minerals and impurity minerals. Under the action of gravity, centrifugal force, mineral particles of different densities undergo stratification and sedimentation, and high-density impurity minerals are separated from low-density aluminum minerals, thus improving the quality. It is suitable for removing impurity minerals with large density differences from aluminum minerals.

[0043] In some implementations, the magnetic separation process employs a vertical ring high-gradient magnetic separator or a pulsed high-gradient magnetic separator; The flotation process employs either a mechanically agitated flotation machine or an aerated agitated flotation machine. The gravity separation process uses a shaking table or a spiral chute.

[0044] In some embodiments, during mineral processing and upgrading, the components of the equipment that come into contact with the slurry or circulating mother liquor are made of alkali-resistant, high-temperature-resistant, and corrosion-resistant materials, selected from titanium and titanium alloys, super austenitic stainless steel, or special ceramics.

[0045] In some embodiments, the magnetic separation iron removal process is arranged after the grinding process and before the leaching process.

[0046] The process described in this application fully utilizes the grinding process to achieve the dissociation of aluminum and iron minerals. The current grinding → magnetic separation → leaching process uses the logic of dissociation followed by separation to remove iron minerals in a single grinding operation, while simultaneously meeting the particle size requirements of the leaching process. This avoids the cumbersome process of conventional processes involving crushing and grinding to remove iron, sedimentation and filtration of the concentrate, and further grinding before entering the alumina process. It also reduces the amount of moisture carried into the alumina process by the concentrate, achieving a triple improvement in quality improvement efficiency, leaching effect, and resource utilization.

[0047] In some embodiments, the yield of the concentrate product corresponding to the concentrate slurry is 72% to 92%, and the content of Al2O3 in the concentrate product is 46.5% to 62.5% by mass fraction, the content of SiO2 is 4.5% to 12%, and the content of Fe2O3 is 1.5% to 22.5%.

[0048] In some implementations, the yield of tailings by-products is 8.5% to 27.5%.

[0049] In some implementations, tailings byproducts include iron concentrate and silicon concentrate.

[0050] In some implementations, the recovered recycled mother liquor is returned to steps S1 and S2 for recycling.

[0051] In some embodiments, the tailings slurry is subjected to sedimentation concentration and / or filtration washing, and the resulting washing liquid is returned to the Bayer process.

[0052] The method for upgrading bauxite mother liquor after grinding provided in this application embodiment can effectively separate aluminum minerals and gangue minerals in bauxite, reduce production costs, improve ore grade, and achieve efficient utilization of bauxite resources, resulting in significant social and economic benefits. In summary, the method for upgrading bauxite mother liquor after grinding provided in this application embodiment has the following advantages: (1) Reduce moisture introduction and lower production costs: Conventional mineral processing and upgrading processes are mainly carried out in aqueous slurry. The resulting aluminum concentrate is filtered after sedimentation and pressure filtration, with a moisture content of 15-20%. This external moisture will enter the subsequent regrinding and leaching processes with the aluminum concentrate, increasing the energy consumption for evaporation. This application embeds the upgrading process between the two inherent processes of grinding and leaching, and carries out upgrading in the circulating mother liquor slurry, avoiding the introduction of moisture and reducing production costs.

[0053] (2) Simplify the process flow and reduce equipment investment and maintenance costs: Conventional mineral processing and upgrading requires dehydration, drying, storage, transportation, and secondary batching and homogenization of the concentrate with the circulating mother liquor, which is a lengthy process. The process of this application is transformed into a direct-through mode of: single-stage grinding → slurry upgrading → direct leaching. The process is essentially simplified, the equipment configuration is compact, the operation control is centralized, no additional auxiliary processes are required, and the process connection is smooth.

[0054] (3) Flexible and scalable modular platform with broad ore adaptability: This application provides a methodological framework and platform technology. The key beneficiation and upgrading unit is a functional module that can be flexibly configured according to the type of target impurities. For iron-based ores, a magnetic separation module can be configured; for silicon-based ores, an alkali-resistant flotation module can be configured. This modular design enables this application to provide an efficient and economical technical solution platform for low-grade bauxite with various impurity characteristics, and has broad ore adaptability.

[0055] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards / industry standards / the disclosure herein; if there are no corresponding national standards / industry standards / the disclosure herein, they are performed according to generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer.

[0056] Example 1 High-iron bauxite was mixed with circulating mother liquor to prepare a slurry, which was then fed into a grinding mill to obtain an alkaline slurry. The high-iron bauxite contained 40.16% Al2O3, 4.20% SiO2, and 31.21% Fe2O3 by mass. The circulating mother liquor temperature was 65℃, the alkaline concentration was 200 g / L, the slurry solids content was 250 g / L, and the proportion of -200 mesh in the slurry was 79.68%. A vertical ring high-gradient magnetic separator was used for magnetic separation to remove iron. The magnetic field strength was 0.9T, and the unloading medium was the circulating mother liquor, which accounted for 15% of the ore weight. After magnetic separation, the alumina content in the concentrate slurry was 46.65%. The magnetic product (iron-rich tailings) was subjected to sedimentation and pressure filtration to obtain an iron concentrate with a Fe2O3 grade of 70.14%. The filtrate was recycled.

[0057] Example 2 Low-grade bauxite was mixed with circulating mother liquor to prepare a slurry, which was then fed into a grinding mill to obtain an alkaline slurry. The low-grade bauxite contained 55.52% Al₂O₃, 21.45% SiO₂, and 2.84% Fe₂O₃, with an A / S ratio of 2.59. The circulating mother liquor temperature was 50℃, the alkaline concentration was 150 g / L, the slurry solids content was 200 g / L, and the -200 mesh content was 84.79%. Aerated flotation was used for desilication, with sodium fatty acid polyoxyethylene ether carboxylate as the collector (600 g / t of raw ore) and ethoxylated alkyl glycoside as the frother (200 g / t of raw ore). The flotation aeration rate was 1.5 m³ / t. 3 / h. The alumina content in the concentrate slurry after flotation is 58.17%, and the A / S ratio is 5.01. The tailings are subjected to sedimentation and pressure filtration, and the filtrate is returned for recycling.

[0058] Example 3 High-iron bauxite was mixed with circulating mother liquor to prepare a slurry, which was then fed into a grinding mill to obtain an alkaline slurry. The high-iron bauxite contained 45.32% Al2O3, 6.33% SiO2, and 22.57% Fe2O3 by mass. The circulating mother liquor temperature was 70℃, the alkaline concentration was 300 g / L, the slurry solids content was 350 g / L, and the proportion of -200 mesh particles in the slurry was 70.22%. A pulsed high-gradient magnetic separator was used for magnetic separation to remove iron. The magnetic field strength was 1.0 T, and the unloading medium was the circulating mother liquor, used at 12% of the ore weight. After magnetic separation, the alumina content in the concentrate slurry was 54.83%. The magnetic product (iron-rich tailings) was subjected to sedimentation and pressure filtration to obtain an iron concentrate with a Fe2O3 grade of 68.51%. The filtrate was recycled.

[0059] Example 4 Low-grade bauxite was mixed with circulating mother liquor to prepare a slurry, which was then fed into a grinding mill to obtain an alkaline slurry. The low-grade bauxite contained 59.63% Al₂O₃, 20.10% SiO₂, and 1.79% Fe₂O₃, with an A / S ratio of 2.97. The circulating mother liquor temperature was 80℃, the alkaline concentration was 250 g / L, the slurry solids content was 400 g / L, and the -200 mesh content was 94.57%. Aerated flotation was used for desilication, with coconut oil fatty acid diethanolamide as the collector (800 g / t of raw ore) and alkyl glycoside phosphate as the frother (250 g / t of raw ore). The flotation aeration rate was 2.5 m³ / t. 3 / h. The alumina content in the concentrate slurry after flotation is 62.32%, and the A / S ratio is 5.75. The tailings are subjected to sedimentation and pressure filtration, and the filtrate is recycled.

[0060] Example 5 Low-grade bauxite was mixed with circulating mother liquor to prepare a slurry, which was then fed into a grinding mill to obtain an alkaline slurry. The low-grade bauxite contained 50.21% Al₂O₃, 23.75% SiO₂, and 6.32% Fe₂O₃, with an A / S ratio of 2.11. The circulating mother liquor temperature was 60℃, the alkaline concentration was 200 g / L, the slurry solids content was 300 g / L, and the -200 mesh content was 76.34%. Gravity separation and desilication were performed using a spiral sluice with a diameter of φ600 mm and a pitch-to-diameter ratio of 0.7. After gravity separation, the concentrate slurry contained 59.31% alumina and an A / S ratio of 5.37. The tailings were subjected to sedimentation and pressure filtration, and the filtrate was recycled.

[0061] Comparative Example 1 Using the high-iron bauxite raw material from Example 1, the upgrading process parameters remained consistent, but the medium was replaced with clean water instead of circulating mother liquor. After upgrading, the alumina content in the concentrate slurry was 46.17%, and the moisture content of the concentrate after filtration was 19.64%. The magnetic product (iron-rich tailings) was subjected to sedimentation and pressure filtration to obtain an iron concentrate with a Fe2O3 grade of 68.34%.

[0062] Comparative Example 2 Using the low-grade bauxite raw material from Example 2, the upgrading process parameters remained the same, but the medium was changed from circulating mother liquor to clean water. After upgrading, the alumina content in the concentrate slurry was 58.39%, the A / S ratio was 4.95, and the water content of the concentrate after filtration was 20.81%.

[0063] Comparative Example 3 Using the high-iron bauxite raw material from Example 3, the upgrading process parameters remained consistent, but the medium was replaced with clean water instead of circulating mother liquor. After upgrading, the alumina content in the concentrate slurry was 54.67%, and the moisture content of the concentrate after filtration was 18.93%. The magnetic product (iron-rich tailings) was subjected to sedimentation and pressure filtration to obtain an iron concentrate with a Fe2O3 grade of 67.92%.

[0064] Comparative Example 4 Using the low-grade bauxite raw material from Example 4, the upgrading process parameters remained the same, but the medium was changed from circulating mother liquor to clean water. After upgrading, the alumina content in the concentrate slurry was 62.41%, the A / S ratio was 5.70, and the water content of the concentrate after filtration was 17.53%.

[0065] Comparative Example 5 Using the low-grade bauxite raw material from Example 5, the upgrading process parameters remained the same, but the medium was changed from circulating mother liquor to clean water. After upgrading, the alumina content in the concentrate slurry was 59.18%, the A / S ratio was 4.99, and the water content of the concentrate after filtration was 21.49%.

[0066] The experimental results of Examples 1-5 and Comparative Examples 1-5 are summarized in Tables 1-3.

[0067] Table 1. Chemical composition and aluminum-silicon ratio of the raw ores in Examples 1-5 and Comparative Examples 1-5

[0068] Table 2. Concentrate product indicators of Examples 1-5 and Comparative Examples 1-5

[0069] Table 3. Tailings product indicators of Examples 1-5 and Comparative Examples 1-5

[0070] As can be seen from the comparison of the test results in Tables 1-3, under the same raw material conditions and process parameters, the technical solution of this embodiment using circulating mother liquor as the sorting medium (Examples 1-5) shows significant technical advantages compared with using clean water as the sorting medium (Comparative Examples 1-5).

[0071] Regarding the separation effect, when the circulating mother liquor was used in the examples, the concentrate yield was generally higher, the alumina content in the concentrate was effectively increased, the aluminum-silicon ratio was significantly improved, and the alumina content in the tailings was lower, indicating that the loss of aluminum minerals during the separation process was smaller and the separation selectivity was better. This shows that the circulating mother liquor, as a separation medium, not only did not have an adverse effect on the separation process, but also, due to its consistency with the media in the grinding and leaching processes, helped maintain the stability of the slurry system, thereby ensuring the realization of efficient separation.

[0072] Regarding the connection of the process flow, the liquid phase of the concentrate slurry obtained in the example is the circulating mother liquor, which is exactly the same as the medium in the subsequent alumina leaching process. Therefore, the concentrate slurry does not need to go through intermediate treatment steps such as dehydration, drying, and re-mixing, and can be directly sent to the leaching process, realizing the seamless connection between the front and back processes and significantly simplifying the process flow.

[0073] In the comparative example, when using water as the separation medium, although the alumina content and aluminum-silicon ratio of the separated concentrate were similar to those in the example, the concentrate slurry needed to be dewatered by pressure filtration, resulting in a concentrate filter cake with a moisture content of approximately 17%–21%. This external moisture, existing in the form of water, will disrupt the water balance of the Bayer process after entering the alumina leaching process with the concentrate, requiring additional steam consumption for evaporation and removal, thus significantly increasing production energy consumption. Furthermore, the addition of the dewatering process also extends the process flow, correspondingly increasing equipment investment and operating costs.

[0074] In summary, the scheme of using circulating mother liquor as the mineral processing and upgrading medium in this invention not only achieves good separation effect, but also fundamentally avoids the introduction of external water, eliminates the additional energy consumption of subsequent evaporation processes, and realizes deep coupling and seamless connection with the Bayer process main process, demonstrating significant technological progress.

[0075] Furthermore, one or more technical solutions in the embodiments of this application have at least the following technical effects or advantages: (1) Systematic process innovation to achieve deep coupling: This invention breaks the boundary between the traditional pre-selection system and the Bayer process main process, and directly embeds the core quality improvement link (mineral processing and quality improvement unit) between the two inherent processes of grinding and leaching in the main process. It achieves deep coupling of the entire process and smooth process connection.

[0076] (2) Closed-loop utilization of the medium eliminates the influence of external water: The Bayer process uses its own circulating mother liquor as the only liquid medium in the entire upgrading process, eliminating the problem of a surge in system steam consumption caused by the introduction of external water, resulting in significant energy-saving benefits. At the same time, the temperature and alkalinity of the mother liquor are consistent with the subsequent leaching requirements, ensuring the stability of the thermal and material balance of the entire process; (3) Simplified process flow and improved technical and economic indicators: The process of mother liquor grinding → mother liquor media separation and upgrading → direct leaching is formed. It eliminates many links in the traditional upgrading process, such as concentrate dewatering, drying, transportation, and re-mixing, as well as the huge auxiliary facilities, which greatly reduces infrastructure investment, operating energy consumption and labor costs.

[0077] (4) Green and environmentally friendly, and recyclable: No wastewater is discharged during the entire process, and the alkaline solution is recycled within the system. The separated impurities (such as iron concentrate and silicon slag) are easier to utilize or safely dispose of because they contain less alkali and are relatively rich in minerals, which reduces the amount of red mud discharged from the source and is environmentally friendly.

[0078] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for upgrading bauxite mother liquor after grinding, characterized in that, The method includes: The mixed slurry of bauxite to be upgraded and the circulating mother liquor is ground to obtain an alkaline slurry in which the aluminum minerals and gangue minerals are fully liberated; the circulating mother liquor is a caustic alkali circulating liquid produced in the alumina leaching process. The circulating mother liquor is used as the sorting and auxiliary medium throughout the process to beneficiate and upgrade the alkaline slurry, so as to separate iron and silicon impurities in the circulating mother liquor medium to obtain concentrate slurry and tailings slurry. The concentrate slurry is fed into the alumina leaching process; The tailings slurry is separated to obtain the circulating mother liquor and tailings by-products.

2. The method according to claim 1, characterized in that, In the bauxite to be upgraded, the content of Al2O3 is 40% to 60% by mass fraction, the content of gangue minerals is 10% to 35%, the content of SiO2 is 40% to 24%, and the content of Fe2O3 is 1.5% to 31.5%.

3. The method according to claim 1, characterized in that, The solids content of the alkaline slurry is 200 g / L to 400 g / L, and the grinding fineness of the alkaline slurry is -200 mesh, accounting for 70% to 95%.

4. The method according to claim 1, characterized in that, The temperature of the circulating mother liquor is 50℃~80℃, and the alkaline concentration of the circulating mother liquor, calculated as NaOH, is 150g / L~300g / L.

5. The method according to claim 1, characterized in that, The mineral processing and upgrading process includes at least one of magnetic separation, flotation, and gravity separation.

6. The method according to claim 5, characterized in that, The magnetic separation process employs a vertical ring high-gradient magnetic separator or a pulsed high-gradient magnetic separator. The flotation process employs a mechanically agitated flotation machine or an aerated agitated flotation machine. The reselection process employs a shaking table or a spiral chute.

7. The method according to claim 1, characterized in that, In the mineral processing and upgrading process, the parts of the equipment that come into contact with the slurry or circulating mother liquor are made of alkali-resistant, high-temperature-resistant, and corrosion-resistant materials, which are selected from titanium and titanium alloys, super austenitic stainless steel, or special ceramics.

8. The method according to claim 1, characterized in that, The yield of the concentrate product corresponding to the concentrate slurry is 72% to 92%, and the content of Al2O3 in the concentrate product is 46.5% to 62.5%, the content of SiO2 is 4.5% to 12%, and the content of Fe2O3 is 1.5% to 22.5% by mass fraction.

9. The method according to claim 1, characterized in that, The yield of the tailings by-products is 8.5% to 27.5%.

10. The method according to claim 9, characterized in that, The tailings by-products include iron concentrate and silicon concentrate.

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