Technical Field
The present invention relates to a beneficiation method for diaspore-type bauxite used in alumina production.
Background Art
China’s bauxite resources are mainly diaspore-type bauxite, characterized by high alumina, high silica, and a low alumina‑to‑silica ratio, with most having an A/S ratio of 4 to 8. Such ores are mostly processed by the lime sintering process and the Bayer‑sintering combined process for alumina production. These two methods have the disadvantages of high energy consumption, long process flow, and large capital investment. However, the Bayer process, which has a simple flow and good economic benefits, requires a raw material with an alumina‑to‑silica ratio (A/S) greater than 10. In order to remove siliceous gangue minerals from bauxite and increase the A/S ratio of the raw material so that it can be used in the Bayer process, extensive research on removing silica minerals by beneficiation methods has been carried out both domestically and internationally since the 1970s, among which flotation desilication is an effective method.
At present, in the flotation process for diaspore-type bauxite, the grinding fineness is greater than 90% passing 0.074 mm, and sodium carbonate, sodium silicate, sodium hexametaphosphate, sodium sulfide, etc. are used as regulators, while sodium oxidized paraffin soap, tall oil, oleic acid, etc. are used as collectors for bauxite flotation desilication. The dosage of sodium carbonate is 2000‑5000 g/t of raw ore, sodium hexametaphosphate is 150‑500 g/t, and the ratio of sodium carbonate to sodium hexametaphosphate is 7‑30:1, with a large dispersant consumption. The collector dosage is 1700‑3200 g/t of raw ore. The main problems of the above process are: high collector consumption, low recovery of coarse diaspore‑rich locked particles, and significant influence of Ca²⁺ and Mg²⁺ contents in the water medium on flotation desilication, which necessitates fine grinding (grinding fineness >90% passing 0.074 mm), resulting in fine concentrate particle size, difficulty in alumina‑silica separation, and difficulty in ensuring both concentrate quality and recovery, thus making it difficult to meet production requirements technically and economically.
Summary of the Invention
In order to overcome the above shortcomings, the present invention provides a bauxite beneficiation method that can effectively recover diaspore and rich locked particles in various water qualities and achieve good desilication effects, by using a combined regulator and a composite collector.
The present invention comprises processes such as ore grinding and direct flotation, and is characterized in that: in a pulp pH range of 7‑12, a combined regulator and a composite collector are added to carry out direct flotation desilication of bauxite, producing a direct flotation concentrate mainly composed of diaspore and its rich locked particles.
(1) The combined regulator is: high‑dosage sodium carbonate + low‑dosage dispersant. The dispersant is one or more of phosphates, polyphosphates, sodium silicate, lignosulfonic acid and its salts, humic acid and its salts, tannin, carboxymethyl cellulose, carboxyethyl cellulose, and fluorine‑containing compounds. The sodium carbonate dosage range is 3000‑8000 g/t of raw ore, the dispersant dosage is 10‑200 g/t of raw ore, the ratio of sodium carbonate to dispersant is 30‑200:1, and the reagent dosages are calculated on the basis of active content.
Under the above dosage and ratio of the combined regulator, the pulp pH for direct flotation desilication can be ensured, the slime can be effectively dispersed, interference of fine gangue on selective alumina‑silica separation can be overcome, siliceous gangue can be selectively depressed, and the flotation of coarse diaspore and its rich locked particles is facilitated.
(2) The composite collector is: a chelating collector + a hydrocarbon‑containing oxygen acid and its salt. The chelating collector is one or more of C₆‑C₁₈ hydroxamic acid and its salts or derivatives, C₄‑C₁₈ oxime organic compounds, cupferron, 8‑hydroxyquinoline, etc. The hydrocarbon‑containing oxygen acid is one or more of fatty acids and their salts or derivatives, hydrocarbon sulfates, and hydrocarbon sulfonates. The chelating collector dosage range is 10‑500 g/t of raw ore, the dosage of hydrocarbon‑containing oxygen acid and its salt is 500‑2500 g/t of raw ore, and the ratio of chelating collector to hydrocarbon‑containing oxygen acid and its salt is 1:250‑1, with reagent dosages calculated on the basis of active content.
The present invention adopts a composite collector that can strengthen the interaction between the collector and diaspore and its rich locked particles, effectively collect coarse diaspore and its rich locked particles, is insensitive to Ca²⁺ and Mg²⁺ ions in water, has low collector consumption, and can obtain a direct flotation bauxite concentrate product with high A/S ratio, high Al₂O₃ recovery, and coarse particle size.
Features of the Invention
By implementing the direct flotation desilication of bauxite according to the present invention, the collecting ability for coarse diaspore‑rich locked particles is strong. Under different water media (total Ca²⁺+Mg²⁺ content of 40‑180 mg/L), the desilication effect on raw materials with different A/S ratios is good, coarse diaspore‑rich locked particles can be effectively recovered, the content of the +0.074 mm fraction in the flotation concentrate is increased by 2%‑23%, and for raw diaspore‑type bauxite ores containing Al₂O₃ 57%‑67%, SiO₂ 8%‑19%, and an A/S ratio of 3‑9, a direct flotation concentrate with an A/S ratio of 10‑20 can be produced. This concentrate can be directly used in the Bayer process for alumina production, with significant economic benefits.
Detailed Description of Embodiments
The present invention is further described below with reference to examples.
Examples:
The following examples are all carried out using a direct flotation process in which bauxite is ground to 55%‑89% passing 0.074 mm, with one stage of roughing, one stage of scavenging, multiple stages of cleaning, and middlings returned in sequence or in a combined manner, producing concentrate and tailings.
1. Combined Regulator
Raw material: A sample from a mine in Henan Province, with the following main chemical composition (wt%) and A/S ratio:
| Al₂O₃ (%) | SiO₂ (%) | Fe₂O₃ (%) | A/S ratio |
|---|---|---|---|
| 65.12 | 11.14 | 6.02 | 5.85 |
Water quality: Total Ca²⁺+Mg²⁺ content = 140 mg/L
Using a composite collector: sodium hydroxamate 100 g/t of raw ore, oleic acid 1100 g/t of raw ore. The closed‑circuit flotation results under different combined regulator dosages and ratios are as follows:
| Example No. | Sodium carbonate (g/t) | Regulator name and dosage (g/t) | Dosage ratio | Concentrate yield (%) | Concentrate A/S ratio | Al₂O₃ recovery in concentrate (%) |
|---|---|---|---|---|---|---|
| 1 | 3000 | Sodium hexametaphosphate 70 | 43 | 83.12 | 11.15 | 90.32 |
| 2 | 4200 | Sodium humate 45 | 93 | 83.08 | 11.28 | 90.35 |
| 3 | 4100 | Sodium lignosulfonate 65 | 63 | 84.57 | 11.03 | 91.20 |
| 4 | 5000 | Polyphosphate + sodium silicate 160 | 33 | 82.17 | 11.56 | 89.48 |
| 5 | 6000 | Carboxymethyl cellulose 30 | 200 | 84.45 | 10.89 | 91.37 |
2. Composite Collector
Raw material: same as Example 1; Water quality: same as Example 1.
Using a combined regulator: sodium carbonate 4000 g/t of raw ore + sodium hexametaphosphate 80 g/t of raw ore. The closed‑circuit flotation results under different composite collector conditions are as follows:
| Example No. | Collector name | Dosage (g/t) | Concentrate yield (%) | Concentrate A/S ratio | Al₂O₃ recovery in concentrate (%) | +0.074 mm fraction in concentrate (%) |
|---|---|---|---|---|---|---|
| 7 | Oleic acid | 2000 | 74.24 | 11.32 | 77.31 | 15.10 |
| 8 | Hydroxamic acid + Oleic acid | 100 + 1200 | 82.12 | 11.89 | 89.87 | 31.85 |
| 9 | 8‑Hydroxyquinoline + Sodium dodecylbenzenesulfonate + Oleic acid | 150 + 500 + 700 | 83.21 | 11.23 | 90.36 | 31.70 |
3. Adaptability to Water Quality
Main chemical composition (wt%) and A/S ratio of the raw material:
| Al₂O₃ (%) | SiO₂ (%) | Fe₂O₃ (%) | A/S ratio |
|---|---|---|---|
| 64.69 | 11.39 | 4.93 | 5.68 |
Combined regulator: sodium carbonate 4200 g/t of raw ore, sodium hexametaphosphate 60 g/t of raw ore.
Composite collector: hydroxamic acid 200 g/t of raw ore, oleic acid 1100 g/t of raw ore.
Closed‑circuit flotation results (with +0.074 mm in the concentrate being 25‑33%) are as follows:
| Example No. | Total Ca²⁺ + Mg²⁺ (mg/L) | Concentrate yield (%) | Concentrate A/S ratio | Al₂O₃ recovery in concentrate (%) |
|---|---|---|---|---|
| 10 | 40 | 80.54 | 14.18 | 91.87 |
| 11 | 100 | 81.40 | 11.73 | 90.58 |
| 12 | 140 | 79.24 | 11.86 | 88.79 |
| 13 | 180 | 79.26 | 11.35 | 87.36 |
4. Adaptability to Raw Ore
Flotation reagent regime: same as in Example 3; total Ca²⁺ + Mg²⁺ content in the flotation water medium: 110 mg/L.
Main chemical composition (wt%) and A/S ratio of the raw material samples:
| Raw ore sample No. | Al₂O₃ (%) | SiO₂ (%) | Fe₂O₃ (%) | A/S ratio |
|---|---|---|---|---|
| 1 | 59.20 | 18.77 | 2.45 | 3.15 |
| 2 | 57.53 | 13.63 | 7.41 | 4.22 |
| 3 | 63.73 | 12.70 | 2.52 | 5.02 |
| 4 | 65.67 | 10.37 | 4.28 | 6.33 |
| 5 | 60.12 | 13.65 | 6.73 | 4.40 |
| 6 | 63.88 | 14.01 | 5.68 | 4.56 |
Closed‑circuit flotation results (with +0.074 mm in the concentrate being 18‑33%) are as follows:
| Example No. | Raw ore sample No. | Concentrate yield (%) | Concentrate A/S ratio | Al₂O₃ recovery in concentrate (%) |
|---|---|---|---|---|
| 14 | 1 | 63.41 | 9.87 | 75.28 |
| 15 | 2 | 71.72 | 10.52 | 85.32 |
| 16 | 3 | 78.36 | 11.03 | 86.58 |
| 17 | 4 | 85.25 | 12.10 | 92.13 |
| 18 | 5 | 70.86 | 12.65 | 84.27 |
| 19 | 6 | 76.93 | 13.76 | 87.88 |
