Method for upgrading low-grade bauxite ore after grinding and flotation of mother liquor

Abstract

The application provides a method for upgrading low-grade bauxite by flotation after grinding, and belongs to the field of mineral processing. The method comprises: grinding a mixed ore slurry of low-grade bauxite and a circulating mother liquor to obtain an alkaline ore slurry; the circulating mother liquor is a caustic alkali circulating liquid generated in an alumina dissolution process; the alkaline ore slurry is sent into a flotation device for desilication treatment by using the circulating mother liquor as a pulp conditioning and froth washing medium to obtain a concentrate slurry and a tailing slurry; the concentrate slurry is sent into an alumina dissolution process; and the tailing slurry is subjected to separation treatment to obtain tailings and the circulating mother liquor. The application places the desilication process after grinding and before dissolution, and uses the circulating mother liquor as a whole-process medium, thereby changing the direction of silicon minerals from the source, and realizing system process optimization and material consumption reduction.

Description

Technical Field

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

[0002] Bauxite is the core raw material for alumina production, and its aluminum-silicon ratio (A / S) directly determines the alkali consumption, leaching efficiency, and economic benefits of the Bayer process. With the increasing scarcity of high-quality bauxite resources, the efficient utilization of low-grade bauxite (A / S below 5) has become crucial for the industry. Low-grade bauxite is characterized by a low aluminum-silicon ratio (typically A / S < 4.0) and generally high SiO2 content (10%–20%), severely restricting alumina production efficiency. During the Bayer process, silica minerals (mainly kaolinite, illite, pyrophyllite, etc.) react with alkali solutions to form sodium aluminosilicate. This not only consumes a large amount of caustic alkali, leading to a surge in alkali consumption, but also results in sodium aluminosilicate entering the red mud, increasing red mud production, exacerbating the environmental pressure of red mud separation and storage, and causing irreversible alumina loss, thus reducing alumina recovery rate.

[0003] Currently, the main technology for processing low-grade bauxite is flotation desilication. Existing technologies generally place the flotation desilication process before the mother liquor grinding process. This involves first coarsely or finely grinding the crushed coarse bauxite, then adding flotation reagents to an aqueous medium or low-alkalinity aqueous solution for flotation. The resulting bauxite concentrate is dewatered, then mixed with Bayer process circulating mother liquor for secondary grinding, and finally sent to the leaching process for leaching. This traditional process has the following core problems: Disruption of system water balance and increased steam consumption: Traditional flotation is conducted in an aqueous solution, and even after dewatering, the resulting concentrate still contains 15%-20% water. This water enters the subsequent Bayer process system with the concentrate. To maintain the alkali concentration and temperature required for leaching, a large amount of additional steam must be consumed for evaporation, leading to a significant increase in production costs. The process is lengthy, cumbersome, and lacks stability: It requires multiple independent steps, including pre-flotation grinding, flotation, concentrate dewatering, and secondary mixing and regrinding with circulating mother liquor. The process is lengthy, involves numerous devices, and has complex control points. Fluctuations in the particle size, concentration, temperature, and alkali concentration of the slurry can affect the stability of the final leaching reaction, leading to significant fluctuations in the alumina leaching rate. Therefore, improving the alumina leaching efficiency, reducing alkali consumption, and minimizing red mud content in low-grade bauxite are urgent technical challenges that need to be addressed. Summary of the Invention

[0004] This application provides a method for upgrading low-grade bauxite mother liquor by flotation after grinding, in order to solve the following technical problems: how to improve the leaching efficiency of alumina in low-grade bauxite, reduce alkali consumption, and reduce the amount of red mud.

[0005] This application provides a method for upgrading low-grade bauxite mother liquor through flotation after grinding. The method includes: The mixed slurry of low-grade bauxite and circulating mother liquor is ground to obtain an alkaline slurry; the circulating mother liquor is a caustic alkali circulating liquid produced in the alumina leaching process. The alkaline slurry is fed into a flotation device for desilication treatment using circulating mother liquor as the slurry conditioning and foam washing 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 tailings and the circulating mother liquor.

[0006] Optionally, in the low-grade bauxite, the content of Al2O3 is 40% to 60% by mass fraction, the content of SiO2 is 10% to 20%, and the aluminum-silicon ratio is 2.0 to 5.0.

[0007] Optionally, the solids content of the alkaline slurry is 250 g / L to 350 g / L, and the grinding fineness of the alkaline slurry is -200 mesh, accounting for 80% to 95%.

[0008] Optionally, the temperature of the circulating mother liquor is 60℃~80℃, and the alkaline concentration of the circulating mother liquor, calculated as NaOH, is 200g / L~260g / L.

[0009] Optionally, the flotation equipment for desilication treatment is a mechanically agitated or aerated agitated flotation machine. The parts of the flotation equipment that come into contact with the slurry are made of materials that are resistant to strong alkalis, high temperatures, and wear. These materials are titanium and titanium alloys, austenitic stainless steel, or special ceramic materials.

[0010] Optionally, the flotation reagents for the flotation desilication treatment include collectors and frothers.

[0011] Optionally, the collector includes: modified fatty acid collector or naphthenic acid soap alkali-resistant collector, and the amount of the collector is 500-1000 g / t of raw ore.

[0012] Optionally, the foaming agent is an alkyl glycoside, and the amount of the foaming agent used is 200-300 g / t of raw ore.

[0013] Optionally, the flotation aeration rate for the flotation desilication treatment is 0.5–2.5 m³. 3 / h.

[0014] Optionally, the aluminum-silicon ratio of the concentrate slurry is ≥6.5.

[0015] The technical solutions provided in this application have the following advantages compared with the prior art: This application provides a method for upgrading low-grade bauxite by flotation after grinding with mother liquor. By placing the flotation desilication process after grinding and before leaching, and using circulating mother liquor as the medium throughout the process, the orientation of silicon minerals is changed from the source, thereby systematically improving leaching efficiency and reducing consumption.

[0016] First, this method selectively separates most of the silica minerals through pre-flotation desilication, before the bauxite enters the leaching process. Since silica minerals (such as kaolinite and illite) are the main substances that react with alkali solutions to form sodium aluminosilicate (sodium silicate slag) during the Bayer process leaching, pre-removal of silica minerals directly reduces the total amount of silica entering the leaching system. Reduced silica entering the leaching system means that the reaction to form sodium aluminosilicate is effectively suppressed, thus avoiding irreversible loss of alumina due to sodium aluminosilicate entering the red mud, thereby improving the alumina leaching efficiency.

[0017] Secondly, the reduction of silica minerals directly reduces alkali consumption. In the Bayer process, the reaction of silica with caustic alkali to form sodium aluminosilicate consumes a large amount of alkali solution. This method removes silica minerals before leaching, cutting off the reaction pathway between the alkali solution and silica minerals at the source. This allows the caustic alkali in the circulating mother liquor to act more efficiently on the leaching of aluminum minerals, significantly reducing the amount of alkali consumed due to the formation of sodium silicate slag.

[0018] Finally, this method effectively reduces the amount of red mud produced. On the one hand, the silica minerals, the main component of red mud, are separated and enter the tailings during the flotation stage, no longer entering the leaching system, directly reducing the basis for red mud formation. On the other hand, due to the reduction of silica minerals in the leaching system, the newly formed sodium aluminosilicate (sodium silicate slag) generated from its reaction with alkali is also reduced simultaneously, further decreasing the total volume of the final red mud. This strategy of reducing silica minerals entering the leaching system at the source not only alleviates the environmental pressure of red mud separation and storage but also reduces the associated treatment costs. Attached Figure Description

[0019] 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.

[0020] 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.

[0021] Figure 1 A schematic flowchart of a method for upgrading low-grade bauxite mother liquor by flotation after grinding, provided for an embodiment of this application; Figure 2 A schematic diagram illustrating the process principle of a method for upgrading low-grade bauxite mother liquor by grinding and flotation, provided in an embodiment of this application. Detailed Implementation

[0022] 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.

[0023] 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.

[0024] Figure 1 A schematic flowchart of a method for upgrading low-grade bauxite mother liquor by flotation after grinding, provided for an embodiment of this application; Figure 2 A schematic diagram illustrating the process principle of a method for upgrading low-grade bauxite mother liquor by grinding and flotation, provided in an embodiment of this application.

[0025] like Figure 1 and Figure 2 As shown in the embodiment of this application, a method for upgrading low-grade bauxite mother liquor by flotation after grinding is provided. The method includes: S1. Grind the mixed slurry of low-grade bauxite and circulating mother liquor to obtain an alkaline slurry; the circulating mother liquor is a caustic alkali circulating liquid produced in the alumina leaching process. S2. Using circulating mother liquor as the slurry conditioning and foam washing medium, the alkaline slurry is fed into the flotation equipment for flotation desilication treatment 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 tailings and circulating mother liquor.

[0026] It should be noted that the grinding and pulping step in S1 is fundamental to the effective separation of minerals and subsequent beneficiation. Its core function is to mix and finely grind low-grade bauxite with the high-temperature, high-alkalinity circulating mother liquor from the alumina leaching process. Through grinding, not only is the bauxite particle size reduced to meet the requirements of subsequent flotation and leaching (typically reaching a fineness of -200 mesh, accounting for 80%–95%), but more importantly, it promotes the full liberation of aluminum and silicon minerals, creating the necessary particle size and degree of liberation conditions for flotation desilication. Simultaneously, using the circulating mother liquor (temperature 60–80℃, alkali concentration 200–260 g / L) as the grinding medium allows for preheating and alkali pre-leaching of the pulp during grinding, ensuring that the pulp's solids content (250–350 g / L), temperature, and chemical environment are highly matched to downstream processes, eliminating the need for separate pulp preparation in traditional processes.

[0027] The mother liquor flotation desilication in S2 is the core separation step of the entire process, responsible for selectively removing silica minerals and improving ore grade. Following grinding and liberation, an alkaline slurry is introduced into an alkali-resistant flotation unit, using the circulating mother liquor as the slurry conditioning and foam washing medium. By adding an alkali-resistant collector (500–1000 g / t) and a frother (200–300 g / t), the differences in the surface physicochemical properties of aluminum and silica minerals are utilized. In the alkaline environment created by the circulating mother liquor, aluminum minerals selectively float hydrophobically, forming concentrate foam, while hydrophilic silica minerals remain in the slurry as tailings. This step innovatively completes the upgrading and separation within the Bayer process's own mother liquor medium, ensuring that the temperature, alkalinity, and concentration of the concentrate slurry are completely consistent with the original system, eliminating process fluctuations caused by medium switching.

[0028] The direct leaching of the S3 concentrate slurry is the final stage for resource conversion and value recovery. The concentrate slurry obtained after flotation desilication has a significantly increased aluminum-to-silicon ratio of over 6.5, and its particle size, concentration, temperature, and alkali concentration perfectly match the feed requirements of the Bayer process leaching. Therefore, this concentrate slurry can be directly pumped to the high-pressure leaching process for alumina leaching without any dewatering, pressure filtration, or secondary slurry preparation. This seamless design completely eliminates the moisture introduction problem caused by concentrate filtration in traditional processes, ensuring stable thermal and water balance in the leaching system and creating ideal conditions for efficient leaching.

[0029] The tailings separation and mother liquor recycling in S4 serve a dual function of resource recovery and environmental friendliness. The tailings slurry from flotation undergoes sedimentation, concentration, filtration, and washing. On one hand, the removed silica minerals are discharged from the system as tailings, reducing the amount of SiO2 entering the leaching process at the source, thereby lowering subsequent alkali consumption and red mud production. On the other hand, through efficient liquid-solid separation, the recycled mother liquor entrained in the tailings is fully recovered and returned to the S1 grinding and S2 flotation stages for reuse. This closed-loop design achieves zero-discharge recycling of high-value caustic soda solution, significantly reducing reagent and alkali consumption costs and demonstrating the green and economical nature of the process.

[0030] In some embodiments, the low-grade bauxite contains 40%–60% Al2O3, 10%–20% SiO2, and has an aluminum-to-silicon ratio of 2.0–5.0 by mass fraction.

[0031] In some embodiments, the solids content of the alkaline slurry is 250 g / L to 350 g / L, and the grinding fineness of the alkaline slurry is -200 mesh, accounting for 80% to 95%.

[0032] The solids content of the pulp is a key process parameter for flotation desilication and subsequent leaching, directly affecting flotation efficiency, gas-liquid-solid three-phase contact, and process stability. A solids content higher than 350 g / L leads to excessive pulp viscosity, uneven bubble dispersion, and difficulty in effectively adsorbing and floating aluminum mineral particles, resulting in alumina loss. Conversely, a solids content lower than 250 g / L reduces the concentration of aluminum mineral particles per unit volume, decreases the probability of collision between bubbles and aluminum minerals, reduces flotation efficiency, decreases equipment processing capacity, and significantly increases energy consumption per unit capacity. Excessive liquid phase during subsequent leaching can lead to excessive system thermal buffering, affecting the precise control of leaching parameters. Examples of pulp solids contents include 250, 280, 300, 320, and 350 g / L.

[0033] Grinding particle size affects the liberation degree of aluminum and silicon minerals in the ore, thus impacting flotation and leaching efficiency. If the grinding fineness is too low, the aluminum and silicon minerals are not fully liberated, resulting in a large amount of aluminum-silicon intergrowth being carried into the concentrate by the collector. This leads to excessive SiO2 content in the concentrate, preventing the aluminum-silicon ratio (A / S) from reaching the standard required for the Bayer process. This directly affects the subsequent alumina leaching efficiency, increases alkali consumption, and some individual aluminum minerals, due to their coarse particles, cannot effectively adhere to air bubbles and enter the tailings along with the silicon minerals, resulting in a decrease in aluminum mineral recovery. If the grinding fineness is too high, a large amount of secondary siliceous slime is generated. This slime covers the surface of aluminum minerals, hindering the selective adsorption of the collector and preventing effective collection of aluminum minerals. The slime also increases the cementitious properties of red mud, making red mud settling and separation difficult. For example, the fineness of the slurry after grinding may be 80%, 85%, 90%, or 95% of the material at -200 mesh.

[0034] In some embodiments, the temperature of the circulating mother liquor is 60°C to 80°C, and the alkaline concentration of the circulating mother liquor, calculated as NaOH, is 200 g / L to 260 g / L.

[0035] In some embodiments, the flotation equipment for desilication treatment is a mechanically agitated or aerated agitated flotation machine. The parts of the flotation equipment that come into contact with the slurry are made of materials that are resistant to strong alkalis, high temperatures, and wear, such as titanium and titanium alloys, austenitic stainless steel, or special ceramic materials.

[0036] In some embodiments, the flotation reagents for desilication flotation include collectors and frothers.

[0037] In some embodiments, the collector includes modified fatty acid collectors or naphthenic acid soap-based alkali-resistant collectors, and the amount of collector used is 500-1000 g / t of raw ore.

[0038] In some embodiments, the foaming agent is an alkyl glycoside, and the amount of foaming agent used is 200-300 g / t of raw ore.

[0039] Bauxite flotation primarily involves altering the hydrophobicity of minerals under specific acid / alkali flotation conditions. This alteration increases the difference between the target mineral and gangue minerals, selectively hydrophobizing the surface of aluminum minerals to allow them to adhere to air bubbles and enter the concentrate, while minimizing the adsorption of silica minerals, thus achieving effective aluminum-silicon separation. Insufficient collector dosage results in only a discontinuous hydrophobic film forming on the aluminum mineral surface, or even no collector adsorption on some aluminum mineral surfaces. This leads to insufficient hydrophobicity of the aluminum minerals, preventing them from effectively binding with air bubbles during their residence time in the flotation cell, reducing separation efficiency. Conversely, excessive collector dosage can lead to the adhesion of excess collector to the silica mineral surface through physical covering or electrostatic adsorption, increasing the hydrophobicity of the silica minerals. This results in some silica minerals being carried into the concentrate along with the aluminum minerals, increasing leaching alkali consumption. Examples of collector dosages are 500, 600, 700, 800, 900, and 1000 g / t of raw ore.

[0040] The core function of frothers is to generate a stable and moderately brittle foam system under specific acid / alkaline flotation conditions. This provides an upward carrier for hydrophobic aluminum minerals, while simultaneously optimizing the surface properties of the slurry to improve bubble-particle collision efficiency. This synergistic effect with the collector achieves efficient aluminum-silica separation. Insufficient frother results in fewer, larger, and more easily broken bubbles in the slurry, leading to an insufficient foam layer height. Hydrophobic aluminum mineral particles cannot effectively collide and adhere to the bubbles, or may detach during ascent due to bubble breakage, preventing the hydrophobic particles from being carried to the foam layer and reducing aluminum mineral recovery. Excessive frother results in overly stable foam, an excessively thick foam layer, and excessively small bubble diameters. This type of foam has strong entrainment properties, carrying large amounts of hydrophilic siliceous mud and silica mineral particles into the concentrate, increasing alkali consumption during leaching. Furthermore, excessive frother entering the concentrate generates a large amount of foam in the Bayer process leaching, affecting the stirring efficiency and heat transfer of the leaching slurry. Examples of foaming agent dosages are 200, 220, 240, 260, 280, and 300 g / t of raw ore.

[0041] In some embodiments, the flotation aeration rate for the desilication process is 0.5–2.5 m³. 3 / h.

[0042] The core function of aeration in flotation is to provide a stable air source for the flotation system, synergistically forming a suitable bubble cluster with the frother, enhancing the interaction between mineral particles, reagents, and bubbles, regulating the flotation froth layer, and ultimately achieving efficient collection of aluminum minerals and effective removal of silica minerals. Insufficient aeration results in a small number of bubbles in the pulp, uneven distribution, and larger, more easily broken bubbles. The low aeration also fails to provide sufficient air source for the frother, preventing it from effectively stabilizing the bubbles. Excessive aeration, on the other hand, causes a sharp increase in pulp turbulence intensity and bubble rising speed. This high-speed turbulence washes away aluminum mineral particles already adhering to the bubble surface, causing them to detach and reducing aluminum mineral recovery. Simultaneously, it synergistically generates numerous small bubbles with the frother, forming an excessively thick and highly stable froth layer that can encapsulate and carry large amounts of silica mineral particles into the concentrate, lowering the concentrate grade. Exemplary flotation aeration amounts are 0.5, 1.0, 1.5, 2.0, and 2.5 m³. 3 / h etc.

[0043] In some implementations, the aluminum-to-silicon ratio of the concentrate slurry is ≥6.5.

[0044] In some embodiments, alkaline pulp flotation desilication occurs after the mother liquor grinding process and before the alumina leaching process.

[0045] This process fully utilizes the grinding process to achieve the dissociation of aluminum and silicon minerals. The current grinding → flotation → leaching process uses the logic of dissociation followed by separation to remove iron minerals in one grinding step, while meeting the particle size requirements of the leaching process. This avoids the cumbersome process of conventional crushing, grinding, desilication → concentrate settling and pressure filtration → re-grinding and mixing. It also reduces the amount of water brought into the alumina process by the concentrate, thereby improving flotation efficiency, leaching effect, and resource utilization.

[0046] This application provides a method for upgrading low-grade bauxite mother liquor through grinding and flotation. This method effectively separates aluminum and silicon minerals in bauxite, reduces production costs, increases ore grade, and achieves efficient utilization of low-grade bauxite resources, resulting in significant social and economic benefits. In summary, the method for upgrading low-grade bauxite mother liquor through grinding and flotation provided in this application has the following advantages: (1) Reduce moisture introduction and lower production costs In conventional flotation desilication processes, the flotation stage is mainly carried out in an aqueous slurry. The resulting aluminum concentrate, after settling and filtration, is pressure filtered, with a moisture content of 15-20%. This external moisture will enter the subsequent regrinding and leaching processes with the aluminum concentrate, adding extra energy consumption for evaporation. This invention shifts the flotation stage to after grinding and before leaching, performing magnetic separation in the circulating mother liquor slurry, avoiding the introduction of moisture and reducing production costs.

[0047] (2) Reduce grinding costs and decrease energy and material consumption. Conventional processes require two grinding stages: a first coarse grinding of the raw ore (to prepare for flotation) followed by a second grinding of the concentrate for pulp preparation. This results in high overall energy consumption. Furthermore, during regrinding of the concentrate, some alumina minerals have already been liberated, and over-grinding can produce a large amount of ultrafine bauxite particles, leading to colloidation and sedimentation difficulties during leaching. This application achieves complete liberation of silica minerals with only one grinding stage, while simultaneously meeting the leaching particle size requirements, reducing grinding energy consumption and the consumption of steel balls / liners.

[0048] (3) Simplify the process flow and reduce equipment investment and maintenance costs. Conventional flotation desilication processes require additional steps such as concentrate settling, filtration, and transportation, increasing equipment maintenance costs. This invention features a tightly integrated grinding, flotation, and leaching process, eliminating the need for additional auxiliary steps and ensuring smooth process flow.

[0049] 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.

[0050] Example 1 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 45.08% Al₂O₃ and 14.36% SiO₂, with an A / S ratio of 3.14. The circulating mother liquor temperature was 65℃, the alkaline concentration was 220 g / L, the slurry solids content was 280 g / L, and the -200 mesh content was 85.14%. Desilication was carried out using a mechanically stirred flotation machine. The collector was sodium methyl ester sulfonate of fatty acids, used at a dosage of 600 g / t of raw ore, and the frother was ethoxylated alkyl glycoside, used at a dosage of 200 g / t of raw ore. The flotation aeration rate was 1.0 m³ / t. 3 / h. The alumina content in the concentrate slurry after flotation is 47.93%, and the A / S ratio is 6.84. The tailings are subjected to sedimentation and pressure filtration, and the filtrate is recycled.

[0051] 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 59.87% Al₂O₃ and 13.57% SiO₂, with an A / S ratio of 4.41. The circulating mother liquor temperature was 80℃, the alkaline concentration was 250 g / L, the slurry solids content was 320 g / L, and the -200 mesh content was 81.03%. Aerated flotation was used for desilication, with sodium fatty acid polyoxyethylene ether carboxylate as the collector (800 g / t of raw ore) and hydroxyl-modified alkyl glycoside as the frother (240 g / t of raw ore). The flotation aeration rate was 2.0 m³ / t. 3 / h. The alumina content in the concentrate slurry after flotation is 63.09%, and the A / S ratio is 11.96. The tailings are subjected to sedimentation and pressure filtration, and the filtrate is returned for recycling.

[0052] Example 3 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 40.29% Al₂O₃, 11.35% SiO₂, and an A / S ratio of 3.55. The circulating mother liquor temperature was 75℃, the alkaline concentration was 200 g / L, the slurry solids content was 250 g / L, and the -200 mesh content was 94.37%. Aerated flotation was used for desilication, with sodium dihydroxystearate as the collector (700 g / t raw ore) and alkyl glycoside phosphate as the frother (280 g / t raw ore). The flotation aeration rate was 0.5 m³ / t. 3 / h. The alumina content in the concentrate slurry after flotation is 43.72%, and the A / S ratio is 7.52. The tailings are subjected to sedimentation and pressure filtration, and the filtrate is returned for recycling.

[0053] 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 50.01% Al₂O₃, 10.49% SiO₂, and an A / S ratio of 4.77. The circulating mother liquor temperature was 70℃, the alkaline concentration was 240 g / L, the slurry solids content was 300 g / L, and the -200 mesh content was 89.54%. Desilication was carried out using a mechanically stirred flotation machine. The collector was sodium fatty acid amide sulfonate at a dosage of 1000 g / t of raw ore, and the frother was carboxymethylated alkyl glycoside at a dosage of 300 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 53.78%, and the A / S ratio is 9.39. The tailings are subjected to sedimentation and pressure filtration, and the filtrate is recycled.

[0054] 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 56.92% Al₂O₃, 19.11% SiO₂, and an A / S ratio of 2.98. The circulating mother liquor temperature was 60℃, the alkaline concentration was 230 g / L, the slurry solids content was 350 g / L, and the -200 mesh content was 83.95%. Aerated flotation was used for desilication, with a naphthenic acid-phosphate composite salt as the collector (900 g / t of raw ore) and an alkyl glycoside phosphate as the frother (260 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 59.79%, and the A / S ratio is 6.62. The tailings are subjected to sedimentation and pressure filtration, and the filtrate is returned for recycling.

[0055] Comparative Example 1 Using the low-grade bauxite raw material from Example 1, the upgrading process parameters remained consistent, but the medium was changed from circulating mother liquor to clean water. After upgrading, the alumina content in the concentrate slurry was 47.90%, the A / S ratio was 6.50, and the water content of the concentrate after filtration was 21.37%.

[0056] 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 63.07%, the A / S ratio was 11.56, and the water content of the concentrate after filtration was 18.59%.

[0057] Comparative Example 3 Using the low-grade bauxite raw material from Example 3, the upgrading process parameters remained consistent, but the medium was changed from circulating mother liquor to clean water. After upgrading, the alumina content in the concentrate slurry was 43.39%, the A / S ratio was 7.43, and the water content of the concentrate after filtration was 19.26%.

[0058] 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 53.77%, the A / S ratio was 9.52, and the water content of the concentrate after filtration was 20.07%.

[0059] 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 59.78%, the A / S ratio was 6.38, and the water content of the concentrate after filtration was 19.84%.

[0060] The test results of the method for upgrading low-grade bauxite mother liquor by grinding and flotation provided in Examples 1-5 and Comparative Examples 1-5 are shown in Tables 1-3.

[0061] Table 1 Chemical composition and aluminum-silicon ratio of low-grade bauxite ore

[0062] Table 2. Flotation concentrate yield, chemical composition and moisture content

[0063] Table 3. Flotation tailings yield and chemical composition

[0064] As shown in Tables 1-3, there is a significant difference in the upgrading effect of using circulating mother liquor as the flotation medium versus using clear water as the flotation medium on low-grade bauxite.

[0065] Regarding the moisture content of the concentrate, the experimental results of Comparative Examples 1 to 5 show that when using water as the flotation medium, the resulting concentrate slurry must undergo pressure filtration, and the moisture content of the concentrate after pressure filtration ranges from 18.59% to 21.37%. This external moisture, existing in the form of water, will enter the alumina leaching process along with the concentrate, inevitably increasing steam consumption in the evaporation process during production. In contrast, Examples 1 to 5 use circulating mother liquor as the grinding and flotation medium throughout the process. The resulting desilication concentrate slurry is an alkaline slurry that meets the temperature and alkalinity requirements of the leaching process, eliminating the need for pressure filtration and dewatering, and can be directly fed into the alumina leaching process, completely avoiding the introduction of external moisture.

[0066] In terms of sorting efficiency and product indicators, the data from Examples 1 to 5 are all superior to those of the comparative examples. The concentrate yields obtained in the examples range from 70.36% to 90.21%, the alumina content in the concentrate increases to 43.72% to 63.09%, and the aluminum-silicon ratio of the concentrate reaches 6.62 to 11.96. In contrast, under the same raw materials and process parameters, the comparative examples, simply by replacing the medium with clean water, showed a slight decrease in concentrate yield and alumina content, and the aluminum-silicon ratio of the concentrate was generally lower than that of the corresponding examples. For example, the aluminum-silicon ratio of the concentrate in Example 1 was 6.84, while that in Comparative Example 1 was 6.50.

[0067] Regarding the tailings products, the tailings obtained in the examples showed higher silica content, a lower aluminum-to-silicon ratio, and lower alumina content. This indicates that using circulating mother liquor as the medium results in better selectivity in the flotation process, more thorough removal of silica minerals, and less loss of aluminum minerals in the tailings.

[0068] Furthermore, one or more technical solutions in the embodiments of this application have at least the following technical effects or advantages: (1) This application completely avoids the introduction of external water and directly uses the circulating mother liquor within the system, which has a matching temperature and alkali concentration, as the only medium in the entire flotation process, without any disturbance to the water balance and heat balance of the main process. It completely solves the problem of increased steam consumption caused by water carried over the concentrate in traditional flotation.

[0069] (2) Simplified process flow and stable operation: A short process flow of mother liquor grinding → mother liquor medium flotation → direct leaching has been formed. The qualified concentrate slurry after flotation meets the requirements for leaching feed in terms of particle size, concentration, temperature and alkalinity. No intermediate dewatering, re-mixing and re-grinding are required, which realizes seamless and stable connection between the front and back processes, and greatly reduces equipment investment and operation and maintenance complexity.

[0070] (3) Green environmental protection and resource recycling: Flotation is carried out in a closed-loop circulating mother liquor, with no additional wastewater generated. After the tailings slurry is settled and filtered, the alkali solution can be completely returned to the system, realizing the recycling of the mother liquor. At the same time, it reduces the SiO2 entering the leaching system from the source, directly reducing the consumption of alkali solution and the output of red mud, resulting in outstanding environmental benefits.

[0071] 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 low-grade bauxite mother liquor through flotation after grinding, characterized in that, The method includes: The mixed slurry of low-grade bauxite and circulating mother liquor is ground to obtain an alkaline slurry; the circulating mother liquor is a caustic alkali circulating liquid produced in the alumina leaching process. The alkaline slurry is fed into a flotation device for desilication treatment using circulating mother liquor as the slurry conditioning and foam washing 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 tailings and the circulating mother liquor.

2. The method according to claim 1, characterized in that, In the low-grade bauxite, the content of Al2O3 is 40%–60% by mass fraction, the content of SiO2 is 10%–20%, and the aluminum-silicon ratio is 2.0–5.

0.

3. The method according to claim 1, characterized in that, The alkaline slurry has a solids content of 250 g / L to 350 g / L, and the grinding fineness of the alkaline slurry is -200 mesh, accounting for 80% to 95%.

4. The method according to claim 1, characterized in that, The temperature of the circulating mother liquor is 60℃~80℃, and the alkaline concentration of the circulating mother liquor, calculated as NaOH, is 200g / L~260g / L.

5. The method according to claim 1, characterized in that, The flotation equipment for desilication treatment is a mechanically agitated or aerated agitated flotation machine. The parts of the flotation equipment that come into contact with the slurry are made of materials that are resistant to strong alkalis, high temperatures, and wear. These materials are titanium and titanium alloys, austenitic stainless steel, or special ceramic materials.

6. The method according to claim 1, characterized in that, The flotation reagents used in the flotation desilication treatment include collectors and frothers.

7. The method according to claim 6, characterized in that, The collector includes modified fatty acid collectors or naphthenic acid soap-based alkali-resistant collectors, and the amount of the collector used is 500-1000 g / t of raw ore.

8. The method according to claim 6, characterized in that, The foaming agent is an alkyl glycoside, and the amount of the foaming agent used is 200-300 g / t of raw ore.

9. The method according to claim 1, characterized in that, The flotation aeration rate for the desilication process is 0.5–2.5 m³. 3 / h.

10. The method according to claim 1, characterized in that, The aluminum-silicon ratio of the concentrate slurry is ≥6.5.

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