This study is based on the selection of refractory fluorite ore in a mining area in Inner Mongolia. The ore structure is complex, and its characteristics are as follows: 1. The ore is high in mud (-200 mesh reaches 31.69%); 2. The impurity mineral in the ore is symbiotic with fluorite; 3. There is a certain amount of iron calcite in the ore. Calcite, limonite, etc., are difficult to choose fluorite ore. The mine was completed and put into operation in June 1990. After many major processes and equipment renovations, high-quality fluorite concentrates are still not available. From the on-site production (Table 1) and past test conditions, the following problems mainly exist: 1. The dissociation degree of useful mineral monomers is not enough; 2. The fluorite concentrate contains SiO ₂ exceeding the standard; 3. The grade of fluorite concentrate is low; 4 Selective investigation of inhibitors; 5, the process structure is unreasonable. The purpose of this study is to develop a technically and economically rational process flow through flotation tests, and to find an effective pharmaceutical system that improves the quality of fluorite concentrates and reduces the amount of impurities.

Table 1 Fluorite concentrate screening and monomer dissociation

First, the nature of the ore

The mine is a medium- and low-temperature hydrothermal metasomatism and filling deposit. There are four types of ore: metasomatic block fluorite ore; metasomatic strip fluorite ore; breccia fluorite ore; fluorite quartz vein. Among them, the latter two ores are more complex in nature. Fluorite-containing quartz veins not only have a low grade of fluorite, but also fluorite is semi-self or his type in the cryptocrystalline or fine-grained quartz veins. The breccia fluorite ore is made of fluorite breccia cemented by later iron minerals, carbonates and siliceous minerals. It has low grade and high iron content, and the granules have a particle diameter of 0.005mm. ~0.030mm quartz.

Fluorspar ore containing, in addition, the gangue minerals are quartz, calcite, limonite, alkali feldspar, iron calcite, kaolin, chlorite, sericite, and a very small amount of apatite and the like. Multi-element analysis results of representative ore samples on site: MgO 0.48, Al ₂ O ₃ 3.66, CaCO ₃ 1.03, Mn 0.064, Fe 6.48, P 0.089, S 0.12, CaF ₂ 62.07, SiO ₂ 18.67.

Second, grinding and floating process test

(1) Five process flows

The ore ore has complex nature and high mud content, which not only consumes a large amount of collector , but also contaminates the surface of the ore, making it difficult to improve the concentrate grade. Due to the lack of water in the mining area, it is not easy to remove the mud in advance. In order to eliminate the impact of the slime on the sorting operation, a reasonable process structure must be adopted to allow the slime to be discharged as early as possible in the flotation operation cycle. Therefore, the following five different structural processes were selected: 1 one-time grinding - 200 mesh up to 90%, six selections, one sweeping, one selected job, abandoned, and the other selected mines returned in sequence To the previous assignment. 2 One-time grinding - 200 mesh up to 90%, six selections, one sweep, the fine one mine abandoned, the rest of the mines returned to the previous operation. 3 One-time grinding - 200 mesh up to 90%, the number of fine and sweeping is the same as 1, 2, only the selected one or two operations in the mine centralized re-election, three or four selected operations in the mine back to a selection In the operation, in the five or six selected operations, the mines will be returned to the second selection operation, and the concentrates will be re-elected and the concentrates will be returned to the rough selection. 4 Re-grinding and re-election process, select a concentrate to re-grind, the mine is discarded, and the fineness is -0.50mm up to 72%. The other selected mines return to the previous operation in sequence. 5 The process structure is the same as 4, and only the regrind fineness is changed to -0.50mm to 90%.

(II) The results of the five process tests are shown in Table 2.

Table 2 Five process test results

(III) Analysis of different process results From the process I and II, it can be seen that the two process concentrate indicators are difficult to pass. The reason is that the internal structure of the process is not suitable for fluorite yield, foam stickiness, poor foam flow, and fine grain size. Features. In the process 3, under the same conditions as the grinding fineness and the chemical conditions, as in the processes 1 and 2, only the internal structure of the process is changed, and the medium ore is concentrated and returned to the primary and secondary selection operations, and the impurity minerals are sufficiently removed. Improve the selection of selected work, which is conducive to the improvement of concentrate grade and satisfactory indicators. Processes 4 and 5 are re-grinding and re-election. It can be seen from the results that the indicators obtained in Process 4 are not satisfactory, and the indicators in Process 5 are the best. The reason is that the mine contains a high amount of mud, coarse grinding can drop a lot of fine mud, reduce the influence of fine mud on the circulation operation, fine grinding of coarse concentrate, make the mineral dissociation fully, a new interface on the mineral surface, easy to catch fluorite The removal of impurity minerals and the re-grinding can reduce the cost of grinding and reduce the cost of chemicals, but the equipment configuration is more complicated than the process 3. According to the site requirements, we choose Process 3.

Third, the process conditions are selected

The crude selection agent test oleic acid is used as a collector of fluorite, which is not only widely used, but also has a good application effect. Most of the new fluorite collectors are in the experimental stage, and they are actually used for production. Especially for quartz-based fluorite ore, oleic acid is still used as a collector. In this study, oleic acid was used as a collector, and the dosage was 0.6-0.8 kg/t.

The adjusting agent is currently used in domestic and international fluorite selection plants, and the pH adjusting agent mostly uses sodium carbonate. It is generally believed that sodium carbonate has two ^[1] 1 hard water softener 2 pH modifiers. This test uses Beijing tap water, its hardness is about 19, the use of sodium carbonate on the one hand can soften the hard water, on the other hand play the role of adjustment value.

The effect of sodium carbonate on the rough selection operation is shown in Figure 1. With the increase of the amount of sodium carbonate, the recovery rate of fluorite gradually increased, while the grade of fluorite first increased slowly and then decreased. This indicates that sodium carbonate has a strong activation effect when oleic acid flotation fluorite, and the quartz is also activated when the dosage is reached to a certain extent. Therefore, the amount of sodium carbonate should be controlled within a certain range, and the pH should be controlled between 9.5 and 10.5. Theoretical studies ^[2] , oleic acid as a collector, in acidic and weakly alkaline media, quartz is not easy to float, but when pH> 10.0, due to the conversion of Ca ^{2 +} and Mg ^{2 +} in the slurry to monovalent Ca The presence of Mg hydroxide ions activates quartz, so when the amount of sodium carbonate is too large, the grade of fluorite coarse concentrate decreases.

Inhibitor: rough selection has been explored using acidified water glass, rubber, water glass and aluminum sulfate combination, lignosulfonate, sodium fluoride, water glass and so on. Among them, the coarse selection index when using water glass is the best. Therefore, the rough selection inhibitor uses water glass, which improves the quality of the fluorite concentrate and places it on the selection of inhibitors for the selected operation.

Fig.1 Relationship between the amount of sodium carbonate and the grade and recovery rate of crude fluorite concentrate

Fig. 2 Relationship between water glass dosage and crude concentrate grade and recovery rate

Figure 2 shows the effect of different water glass dosages on flotation. When the amount of water glass is small, it has an activation effect on fluorite and exhibits effective inhibition of gangue minerals. However, when the amount exceeds a certain range, it exhibits inhibition of fluorite. Therefore, the amount should be strictly controlled in production. Studies on the mechanism of sodium silicate fluorite many ^{[3, 4]} is generally believed, by inhibiting properties of waterglass pH, concentration, part of the metal ions, temperature of the slurry itself modulus and the like.

(2) Temperature test

In the practice of oleic acid flotation fluorite, heating flotation is often used, which has two functions: 1 changing the adsorption form of oleic acid on the surface of fluorite; 2 increasing the solubility of oleic acid. The effect of temperature on flotation is shown in Figure 3. The suitable temperature is 37 °C. The test uses hot water temperature regulation.

Figure 3 Relationship between temperature and crude ore concentrate grade and recovery rate

(III) Selected Tests We put the quality of fluorite concentrate on selected operations. In order to achieve high quality concentrates and to ensure recovery, selective and highly effective inhibitors must be used. Tests have shown that qualified concentrates are not obtained with single water glass as inhibitors. Therefore, this experiment has used a large number of exploratory tests using acidified water glass, silicone rubber, citric acid, sodium hexametaphosphate, acidified CMC, A ₁₀ , A ₂₀ and various possible mixed drugs. It was found that A ₁₀ (mixed inhibitor, polyhydroxy compound) has strong selective inhibition effect on quartz, iron calcite, limonite, etc., and mixed with water glass can obtain better selection index. A ₁₀ is a non-toxic, odorless, soluble, and affordable organic material with a small amount. At a total amount of 0.14 kg/t, a fluorite concentrate having CaF ₂ >97% and SiO ₂ <1% can be obtained. This proves that A ₁₀ is used in combination with water glass and is a selective selective inhibitor (Fig. 4).

Figure 4 Relationship between total A ₁₀ content and concentrate grade and recovery rate

(4) Impact of water quality on flotation

The impact of water quality on flotation, especially on fluorite flotation, is more obvious. We carried out flotation tests on different water quality of on-site production water and Beijing tap water. Tests have shown that on-site water is not conducive to the flotation of fluorite, and the adjustment agent sodium carbonate cannot eliminate its effect on flotation. After testing, it was found that this effect can be eliminated by using H ₁₀ base regulator. The test results are shown in Table 3.

Table 3 Test results of H ₁₀ instead of NaCO ₃

It can be seen from Table 3 that the substitution of H _{10 for} NaCO ₃ can eliminate the effect of water quality on flotation, and the amount thereof is preferably 1.0 kg/t.

In order to find out the cause, we tested the on-site water with a hardness of 5.8. Type, hardening degree 1.924 ~ 2.04g / L, Cl ^- 726.9 ~ 886.4mg / L, SO ^{2 -} ₄ 378, 7 ~ 492.8mg / L. Compared with Beijing tap water: 1 hardness is small (Beijing water hardness is about 19); 2 mineralization degree, high content of Cl ^- and SO ^{2 -} _{4 is} high. It can be seen that the cause of unfavorable flotation is not the hardness of water, but may be caused by high levels of anions in the water. In order to eliminate this effect, H ₁₀ can be used to obtain satisfactory screening indicators.

Fourth, the conclusion

1. Reasonable process structure is an important means to obtain qualified concentrates.

2. The use of highly selective inhibitors can make fluorite concentrates of high quality. For this study ore, water glass and A ₁₀ are an effective combination inhibitor.

3. Different water quality must use different adjusting agents to achieve the desired flotation effect. In this experiment, H ₁₀ can eliminate the adverse effect of high anion water on fluorite flotation. In hard water with low anion, Na ₂ CO ₃ regulator can achieve good sorting effect.

4. Fluorite ore with high mud content and fine grain size. Re-grinding with coarse concentrate is an effective measure to eliminate the influence of slime and obtain qualified concentrate.

references

1. M·A·Egris. Flotation Adjustment Agent. Beijing: Metallurgical Press, 1990.

2. Fuerstenau M.C. Flotation Chemistry (English). Society of Mining Engineers, New York, 1985.

3, Wang Dianzuo et al. Flotation solution chemistry. Changsha: Hunan Science and Technology Press, 1988.

4, Song Ganggong, etc. Research on the role of flotation of sodium silicate. Foreign metal ore dressing , 1976 (4).

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