A method for desilication of high-silica bauxite by reverse flotation
By using reverse flotation desilication technology, combined with activators and inhibitors, and optimizing the reagent system, the problems of high reagent cost and difficult foam transportation in direct flotation have been solved, achieving efficient desilication of bauxite and recovery of alumina.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CENT SOUTH UNIV
- Filing Date
- 2026-05-09
- Publication Date
- 2026-06-30
AI Technical Summary
The existing positive flotation desilication process is poorly adapted to bauxite with high mud content, has high reagent costs, and is difficult to transport and defoam, which affects production operations. Furthermore, it is difficult to dewater the aluminum concentrate product.
The reverse flotation desilication method is adopted, combining activators, collectors and depressants, and optimizing the reagent system, including diaspore depressants, anionic collectors and metal ion activators, controlling the pH value under neutral or weakly acidic conditions for flotation, and optimizing the grinding fineness and reagent dosage.
It improved the aluminum-silicon ratio and alumina recovery rate of bauxite concentrate, reduced reagent costs, improved foam viscosity and defoaming difficulty, and simplified the process flow.
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Figure CN122298585A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of mineral flotation separation technology, specifically to a method for reverse flotation desilication of high-silica bauxite. Technical Background
[0002] Aluminum is a silvery-white metal with low density and light weight. It possesses good ductility, electrical conductivity, thermal conductivity, heat resistance, and radiation resistance. In air, aluminum forms a dense oxide film on its surface, giving it excellent corrosion resistance. Due to its abundance and excellent properties, aluminum has become the world's second most consumed metal after steel. It is commonly made into various shapes such as rods, sheets, and foils and is widely used in important industrial sectors such as aerospace, construction, automotive, and power.
[0003] Bauxite is the primary raw material for the industrial production of metallic aluminum. It mainly refers to a mineral aggregate primarily composed of diaspore, boehmite, and gibbsite. Since Bayer optimized the Bayer process for alumina production in 1889, bauxite resources have become a crucial mineral resource supporting human economic development. Approximately 90% of the world's alumina is produced using the Bayer process, but this process requires bauxite raw materials with an aluminum-to-silicon ratio (ASI) of at least 8. However, over 70% of my country's bauxite ore has an ASI below 7, which does not meet the requirements of the Bayer process. Therefore, pre-desiliconization treatment of the bauxite is necessary to increase its ASI to meet the requirements of this production process.
[0004] Bauxite is typically desilicated using direct flotation. For example, patent CN119406577A describes a desulfurization and desilication process for high-sulfur, high-silica bauxite, employing a process of first reverse flotation for desulfurization, followed by direct flotation for desilication. Commonly used collectors in existing direct flotation desilication processes can be categorized as follows: fatty acids and soaps, sulfonates, and hydroxamic acids. However, current direct flotation has several drawbacks: 1. Poor adaptability to bauxite with high mud content, resulting in large fluctuations in process parameters. 2. A large variety and dosage of reagents are required to handle slime and complex minerals, leading to excessively high yields. 3. Undissolved reagents remain in the bauxite concentrate obtained from direct flotation, making the concentrate viscous and hindering dewatering and filtration. 4. Collectors remain in the bauxite concentrate, causing side effects in subsequent Bayer process alumina production. Therefore, in recent years, reverse flotation desilication technology has received more attention and research for these difficult-to-process ores to overcome the inherent shortcomings of direct flotation.
[0005] Amine collectors are commonly used for desilication of bauxite via reverse flotation. For example, patent CN119747097A describes the use of amine collectors for desilication, but these collectors are relatively complex. While amine collectors combined with gibbsite depressants can effectively perform desilication via reverse flotation, they suffer from drawbacks such as high reagent cost, strong foaming properties, sticky foam, and sensitivity to slime. In actual production, this leads to difficulties in foam transport and defoaming, affecting operational efficiency. Therefore, it is necessary to invent a cost-effective and efficient method for desilication of high-silica bauxite via reverse flotation. Summary of the Invention
[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for desilication of high-silica bauxite via reverse flotation. This method, through the process concept of reverse flotation desilication combined with activators, collectors, and depressants, achieves the desilication target of high-silica bauxite, resulting in bauxite concentrate with a high aluminum-silicon ratio and high alumina recovery rate. This method has advantages such as low reagent cost, improved foam viscosity, reduced defoaming difficulty, and simple process.
[0007] To achieve the above-mentioned technical objectives, the present invention provides a method for reverse flotation desilication of high-silica bauxite. The method uses high-silica bauxite as the processing object. The raw ore is crushed, ground, and slurry-adjusted to obtain a slurry. After the slurry is adjusted to 5.0-9, a diaspore inhibitor, an activator, and an anionic collector are added for reverse flotation desilication. The froth product is mainly kaolinite, and the residue at the bottom of the tank is bauxite concentrate. The high-silica bauxite contains an aluminum content of greater than or equal to 65 wt%.
[0008] As a preferred embodiment, the present invention involves grinding the ore to a fineness of -200 mesh, where the mass of the particles accounts for 80%-90% of the total particle mass; and the pulp concentration is 30wt%-40wt%. The purpose of grinding is to effectively liberate gangue minerals such as kaolinite and gibbsite monohydrate, which is beneficial for subsequent flotation separation. In industrial applications, grinding can generally be completed in 10-20 minutes.
[0009] As a preferred embodiment, the pH adjustment agent for the slurry is sodium hydroxide or hydrochloric acid, with a dosage relative to the raw ore of 100-500 g / t; and the pH is maintained at 5.0-9 throughout the slurry preparation process, more preferably 6.5-7.5, and even more preferably 6.8-7.2, which naturally includes 7. This invention achieves efficient and rapid reverse flotation of silicon only under weakly acidic or neutral conditions. If the alkalinity of the slurry is too high, it will lead to problems such as poor flotation performance of kaolinite.
[0010] As a preferred embodiment, the diatomite inhibitor is selected from one or a mixture of several of water glass, tannic acid, sodium pyrophosphate, and polyacrylamide.
[0011] The amount of water glass or polyacrylamide used relative to the raw ore is 2000-3500 g / t; the amount of tannic acid and sodium pyrophosphate used relative to the raw ore is 50-200 g / t.
[0012] As a preferred embodiment, the activator is selected from one of copper sulfate, lead acetate, and aluminum chloride, with a relative dosage of 1000-2500 g / t of raw ore. Metal ions can activate kaolinite under suitable pH conditions without activating diaspore (including diaspore monohydrate), facilitating their separation. Furthermore, metal ions can improve the problems of excessive foam and high viscosity during flotation; copper sulfate is a further preferred option.
[0013] As a preferred embodiment, the anionic collector is selected from one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and sodium dodecyl sulfonate, with a relative dosage of 400-1000 g / t relative to the raw ore; sodium dodecyl sulfate is more preferred.
[0014] As a preferred approach, a reagent system employing tannic acid and water glass as a combined dester at a mass ratio of 1:20-1:100, more preferably 1:20-25, copper sulfate as an activator, and sodium dodecylbenzenesulfonate as a collector, exhibits good desilication performance in reverse flotation. This further enhances the aluminum-silicon ratio in the product.
[0015] As a preferred embodiment, the reverse flotation desilication process consists of one roughing and one scavenging phase.
[0016] As a preferred embodiment, the reagent dosage in the scavenging reagent system during the reverse flotation desilication process is 1 / 4 to 1 / 2 of that used in the roughing process.
[0017] As a preferred embodiment, the reverse flotation is carried out at a stirring speed of 1900-2300 r / min.
[0018] This invention provides a method for desilication of high-silica bauxite by reverse flotation, specifically including the following steps:
[0019] (1) The high-silica bauxite is crushed, ground, and slurry-adjusted to obtain a slurry with suitable particle size and concentration;
[0020] (2) Add appropriate amounts of pH adjuster, inhibitor, activator and collector to the slurry to be treated in sequence. After each addition of reagents, wait 2-4 minutes to allow the reagents and slurry to react fully and ensure that the pH of the slurry remains constant throughout the process.
[0021] (3) Under neutral conditions, a roughing and a scavenging process is used to obtain foam products (mainly kaolinite) and bottom products (bauxite concentrate).
[0022] According to the present invention, after optimization, the aluminum-silicon ratio of the obtained bauxite concentrate is greater than 8.0 and the recovery rate is greater than 80%.
[0023] Compared with existing technologies, the advantages of this invention patent are:
[0024] (1) The present invention is preferably carried out under neutral or weakly acidic conditions to avoid corrosion of mineral processing equipment and pipelines under acidic conditions.
[0025] (2) The present invention adopts the reverse flotation desilication method, which overcomes the problems of large reagent consumption, high cost and difficulty in dewatering concentrate products in the direct flotation desilication process.
[0026] (3) This invention employs a reagent system combining metal ions as activators with anionic collectors to float gangue minerals such as kaolinite. Because metal ions possess the ability to weaken the foaming properties of collectors, this greatly improves problems such as excessive foam, high viscosity, and difficulty in defoaming during the flotation process. Furthermore, compared to amine collectors, the combination of metal ions and anionic collectors reduces reagent costs. Attached Figure Description
[0027] Figure 1 This is a process flow diagram of a method for desilication of high-silica bauxite by flotation according to the present invention.
[0028] Figure 2 This is the XRD pattern of the raw materials used in Example 1 of the present invention. Detailed Implementation
[0029] The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the invention. Any modifications and substitutions made to the method steps or conditions of the present invention without departing from the spirit and essence of the invention are within the scope of the invention.
[0030] Example 1
[0031] This embodiment uses high-silica bauxite from Zunyi, Guizhou Province as raw material. Measurements showed that the Al₂O₃ and SiO₂ contents in this high-silica bauxite were 62.17% and 13.42%, respectively; the aluminum-silica ratio was 4.63. The X-ray diffraction pattern of this ore is shown below. Figure 2 It can be seen that the main components of the ore are bauxite and kaolinite.
[0032] This case study provides a method for desilication of high-silica bauxite by reverse flotation, which specifically includes the following steps:
[0033] (1) Place 500 g of high-silica bauxite ore in a ball mill and grind for 16 min until the grinding fineness reaches 80% or more of the -200 mesh. Put the ground product that has reached the fineness into a 1.5L flotation machine, add an appropriate amount of water to adjust the slurry concentration to 35%.
[0034] (2) Add an appropriate amount of sodium hydroxide to adjust the pH of the pulp to 7.0. The pulp pH must be maintained at 7.0 throughout the entire flotation process. Add 3000 g / t of inhibitor (water glass), 1500 g / t of activator (copper sulfate), and 350 g / t of collector (sodium dodecyl sulfate) in sequence. After each addition of reagents, adjust the pH to 7.0 and allow it to react with the pulp for 3 minutes. Then, aerate for 1 minute and scrape the foam for 5 minutes to perform a roughing process, obtaining frothy product and roughing tailings. Then, maintain the pulp pH at 7.0, reduce the amount of inhibitor by one-third, and halve the amounts of activator and collector to perform a scavenging process, obtaining frothy product and residual bottom product. The residual bottom product is bauxite concentrate.
[0035] After steps (1-2), high-purity bauxite concentrate can be obtained. The bauxite concentrate contains 69.87% Al2O3 and 6.91% SiO2, with an aluminum-to-silicon ratio of 10.11 and a bauxite recovery rate of approximately 85%.
[0036] Example 2
[0037] This embodiment differs from Example 1 only in that the collector in step (2) is replaced with sodium dodecylbenzenesulfonate at a relative amount of 400 g / t of raw ore; all other steps and conditions are the same.
[0038] After steps (1-2), high-purity bauxite concentrate can be obtained. The bauxite concentrate contains 68.82% Al2O3 and 7.52% SiO2, with an aluminum-silicon ratio of 9.15 and a bauxite recovery rate of approximately 80%.
[0039] Example 3
[0040] This embodiment differs from Example 1 only in that the inhibitor in step (2) is replaced with tannic acid at a relative amount of 60 g / t of raw ore; all other steps and conditions remain the same.
[0041] After steps (1-2), high-purity bauxite concentrate can be obtained. The bauxite concentrate contains 69.25% Al2O3 and 7.00% SiO2, with an aluminum-silicon ratio of 9.89 and a bauxite recovery rate of approximately 82%.
[0042] Example 4
[0043] This embodiment differs from Example 1 only in that the activator in step (2) is replaced with lead acetate at a relative amount of 1800 g / t of the original ore, and the slurry pH is adjusted to 6.0. All other steps and conditions are the same.
[0044] After steps (1-2), high-purity bauxite concentrate can be obtained. The bauxite concentrate contains 68.97% Al2O3 and 7.45% SiO2, with an aluminum-to-silicon ratio of 9.26 and a bauxite recovery rate of approximately 80%.
[0045] Example 5
[0046] This embodiment differs from Example 1 only in that the activator in step (2) is replaced with aluminum chloride at a relative amount of 1500 g / t of raw ore, and the slurry pH is adjusted to 5.0. All other steps and conditions are the same.
[0047] After steps (1-2), high-purity bauxite concentrate can be obtained. The bauxite concentrate contains 69.13% Al2O3 and 7.00% SiO2, with an aluminum-to-silicon ratio of 9.87 and a bauxite recovery rate of approximately 80%.
[0048] Example 6
[0049] This embodiment differs from Example 1 only in that the inhibitor in step (2) is replaced with tannic acid at a relative amount of 50 g / t and 1000 g / t relative to the original ore, while the remaining steps and conditions are the same.
[0050] After steps (1-2), high-purity bauxite concentrate can be obtained. The bauxite concentrate contains 71.98% Al2O3 and 6.68% SiO2, with an aluminum-to-silicon ratio of 10.78 and a bauxite recovery rate of approximately 82%.
[0051] Exploration Example 1
[0052] This exploratory example differs from Example 1 only in that the amount of activator in step (2) is changed to 1000 g / t, and no inhibitor is added. All other steps and conditions are the same.
[0053] After steps (1-2), high-purity bauxite concentrate can be obtained. The bauxite concentrate contains 65.58% Al₂O₃ and 9.21% SiO₂, with an aluminum-to-silicon ratio of 7.12 and a bauxite recovery rate of approximately 68%. Compared to Example 1, in this comparative example, when only metal ion and anion collectors were used in the reverse flotation desilication process, the flotation entrainment was large, and some gibbsite monohydrate was carried over to the froth product, resulting in a decrease in the Al₂O₃ grade and aluminum-to-silicon ratio in the bottom product.
[0054] Exploration Example 2
[0055] The only difference between this exploratory example 2 and example 1 is that the pH of the slurry in step (2) is adjusted to 6.0, while the rest of the steps and conditions are the same.
[0056] After steps (1-2), bauxite concentrate was obtained. The bauxite concentrate contained 66.12% Al₂O₃ and 14.52% SiO₂, with an aluminum-to-silicon ratio of 4.53 and a bauxite recovery rate of approximately 49%. Compared to Example 1, in this comparative example, the pH was only lowered from 7.0 to 6.0 during the reverse flotation desilication process, resulting in a significant difference in flotation results. This is because at pH 7.0, copper sulfate has an activating effect on kaolinite, and when combined with sodium dodecyl sulfate, kaolinite can be floated. Furthermore, at this pH, copper sulfate adsorbs little or no on the surface of gibbsite monohydrate, having no activating effect. Instead, copper sulfate reacts with sodium dodecyl sulfate, thereby damaging the collector's collecting performance and reducing the gibbsite monohydrate recovery rate. This is why copper sulfate acts as an activator in combination with anionic collectors such as sodium dodecyl sulfate to separate kaolinite and gibbsite monohydrate. However, at pH 6.0, copper sulfate does not have this effect, leading to poorer flotation results.
[0057] Exploration Example 3
[0058] The only difference between this exploratory example 3 and example 1 is that the pH of the slurry in step (2) is adjusted to 9.0, while the rest of the steps and conditions are the same.
[0059] After steps (1-2), bauxite concentrate is obtained. The bauxite concentrate contains 64.21% Al2O3 and 13.02% SiO2, with an aluminum-to-silicon ratio of 4.93 and a bauxite recovery rate of approximately 90%.
Claims
1. A method for desilication of high-silica bauxite by reverse flotation, characterized in that: Using high-silica bauxite as the processing target, the raw ore is crushed, ground and slurry adjusted to obtain slurry; after the slurry is adjusted to 5.0-9, diaspore inhibitor, activator and anionic collector are added for reverse flotation desilication, the froth product includes kaolinite, and the residue at the bottom of the tank is bauxite concentrate, the high-silica bauxite contains aluminum content greater than or equal to 65wt%.
2. The method for desilication of high-silica bauxite by reverse flotation according to claim 1, characterized in that: The grinding process is such that the mass of the -200 mesh particles accounts for 80%-90% of the total particle mass; the slurry concentration is 30wt%-40wt%.
3. The method for reverse flotation desilication of high-silica bauxite according to claim 1, characterized in that: The pH adjustment agent for the slurry is sodium hydroxide or hydrochloric acid, with a relative dosage of 100-500 g / t of raw ore; and the pH is maintained at 5.0-9 throughout the slurry preparation process, more preferably 6.5-7.5, and even more preferably 6.8-7.2, which of course includes 7.
4. The method for desilication of high-silica bauxite by reverse flotation according to claim 1, characterized in that: The diatomite inhibitor is selected from one or a mixture of several of water glass, tannic acid, sodium pyrophosphate, and polyacrylamide.
5. The method for reverse flotation desilication of high-silica bauxite according to claim 4, characterized in that: The amount of water glass or polyacrylamide used relative to the raw ore is 2000-3500 g / t; the amount of tannic acid used relative to the raw ore is 50-200 g / t; and the amount of sodium pyrophosphate used relative to the raw ore is 50-200 g / t.
6. The method for reverse flotation desilication of high-silica bauxite according to claim 1, characterized in that: The activator is selected from one of copper sulfate, lead acetate and aluminum chloride, and the relative amount used is 1000-2500 g / t of raw ore.
7. The method for desilication of high-silica bauxite by reverse flotation according to claim 1, characterized in that: The anionic collector is selected from one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and sodium dodecyl sulfonate, with a relative dosage of 400-1000 g / t of raw ore; sodium dodecyl sulfate is more preferred.
8. The method for reverse flotation desilication of high-silica bauxite according to claim 4, characterized in that: Tannic acid and water glass are used as a combined inhibitor in a mass ratio of 1:20-1:100, more preferably 1:20-25. Copper sulfate is used as an activator, and sodium dodecylbenzenesulfonate is used as a collector. The reverse flotation desilication process consists of one roughing and one scavenging phase.
9. The method for desilication of high-silica bauxite by reverse flotation according to claim 1, characterized in that: In the reverse flotation desilication process, the reagent dosage in the scavenging reagent system is 1 / 4 to 1 / 2 of that in the roughing process.
10. The method for reverse flotation desilication of high-silica bauxite according to claim 1, characterized in that: All reverse flotation was carried out at a stirring speed of 1900-2300 r / min.