Experimental Study on Beneficiation of a Molybdenum Ore in Qinghai

China's molybdenum mines are large in scale. Large-scale molybdenum deposits with a reserve of more than 100,000 tons account for 76% of the country's total reserves. The medium-sized deposits with a storage capacity of 10,000 to 100,000 tons account for 20% of the country's total reserves. As far as the ore type is concerned, in the proven reserves of molybdenum ore in China, the molybdenum sulfide ore is mainly used for utilization, and its reserves account for about 99% of the total retained reserves of molybdenum ore, and the molybdenum oxide ore, which is not convenient for use, is mixed with molybdenum. Ore and unidentified molybdenum ore account for only 1% of the country's total reserves. Strengthening the ore dressing experimental research on molybdenum sulfide ore is of great significance for the effective utilization of molybdenum ore resources. A large skarn-type molybdenum deposit has recently been discovered in Qinghai. The experimental study on the technical conditions of the flotation process for the molybdenum ore is described in detail.

First, the nature of the ore

(1) The chemical composition of the original ore

Table 1 Analysis of main chemical components of ore (%)

Table 1 shows that the original ore Mo content 1.04%, the other associated with a low polyvalent metal content, low P, As detrimental elements.

(2) Mineral composition and its inlay characteristics

The metal ore in the original ore is simple in composition, the main metal mineral is molybdenum ore, and the main gangue minerals are garnet and diopside . The mineral composition of the ore is shown in Table 2. The characteristics of the main metal minerals; the molybdenum ore is semi-automorphic - it is scaly, distributed in a non-uniform mass and disseminated between the garnet particles. The molybdenite disseminated aggregate has a particle size of 0.1 to 1.2 mm, wherein the content of 0.1 to -0.4 mm is 10.0%, +0.4 to -0.6 mm 70%, and +0.6 to -1.2 mm 20.0%. It was shaped pyrite present in the particulate garnet micro-cracks, the particle size ≤0.02mm.

Table 2 Raw ore mineral composition

Second, the test results and discussion

The ore is a typical skarn-type molybdenum ore. The original ore contains 1.04% molybdenum and 0.96% sulfur. According to the nature of the ore, the experimental results show that the ore composition is simple and the molybdenum can be realized by flotation process. The mineral is separated from the gangue.

The silicate gangue such as diopside and sericite contained in the original ore is easy to be muddy. The adsorption of the fine mud reduces the efficacy and increases the viscosity of the slurry, so that the fine mud adheres to the surface of the molybdenum ore. The wrap layer affects the flotation of molybdenum ore and adds water glass to overcome the effects of slime. The test results show that the water glass can strongly inhibit the silicate gangue, and at the same time, it has anti-flocculation effect on the fine mud. When the amount of water glass is appropriate, the dispersed fine mud can be selectively adsorbed, so that the surface of the fine mud is hydrophilized to inhibit precipitation, reduce the viscosity of the slurry, and reduce the pollution of the surface of the molybdenite by the fine mud. The molybdenum ore is released from the fine flocs, improving the flotation process and increasing the flotation index.

Effect of the flotation collector: This test uses kerosene as a collector, pine oil compound 101 as a foaming agent. Kerosene has a good selectivity for the selection of molybdenum ore. The comparison test of 101 compound pine oil with 2# oil shows that 101 composite pine oil has strong foaming performance and less dosage. It is used in molybdenite to improve the recovery rate and improve the quality of molybdenum concentrate.

The rough-selected molybdenum concentrate was re-polished and then selected and compared to the non-grinding direct comparison test to examine the effect of the re-grinding after selection. The comparison test results show that, due to the sufficient dissociation of the crude molybdenum concentrate monomer, the grinding will cause the molybdenum ore to be pulverized and cause it to be difficult to select, and the regrind will further increase the slime, so the pre-selection is coarse. The molybdenum concentrate is no longer ground for grinding.

(2) Test of rough selection conditions

1. Influence of grinding fineness on flotation index

The grinding fineness test process conditions are 60g/t of kerosene, 24g/t of 101 composite pine oil, and 4min of flotation time. The relationship between different grinding fineness and flotation index is shown in Fig. 1. With the increase of grinding fineness, the molybdenum beneficiation index is gradually increased. When the grinding fineness is -200 mesh 90%, the molybdenum recovery rate is 86.0%, and the molybdenum beneficiation index has a downward trend. This indicates that when the grinding fineness is low, the molybdenum ore particles cannot be dissociated from the gangue mineral monomer, and the particles are heavy, can not be effectively floated, easily cause over-grinding, and are applied to the surface of the gangue mineral to make this part of the gangue Enter the concentrate and affect the quality. In addition, the overgrown sludge increases the flotation environment, resulting in a decrease in the recovery rate of molybdenum.

Figure 1 Grinding fineness test results [next]

2, water glass dosage test

The water glass dosage test was carried out under the conditions of grinding fineness of -200 mesh 90%, kerosene dosage of 60 g/t, 101 composite pine oil consumption of 24 g/t, and flotation time of 4 min. It is shown in Fig. 2 that with the increase of the amount of water glass, the molybdenum recovery rate first increases and then decreases when the molybdenum grade does not change much. When the amount of water glass is 500g/t, the coarse selection can obtain the technical index of the molybdenum recovery rate of 93.10% and the molybdenum grade of 36.78%.

Figure 2 Results of rough selection of water glass

3. Kerosene dosage test

The kerosene dosage test was carried out using the conditions of the above tests. It is shown in Fig. 3 that with the increase of the amount of kerosene, the recovery rate of molybdenum increases. When the amount of kerosene is 60g/t, the recovery index tends to be stable. For this reason, the optimum dosage of kerosene is determined to be 60g/t.

Figure 3 kerosene dosage test results

(2) Selected trials

The test results of the selected operation water glass dosage are shown in Figure 4. It can be seen from Fig. 4 that the addition of proper amount of water glass in the selection is beneficial to the improvement of the beneficiation index. When the amount of water glass is 50g/t, the recovery rate of molybdenum concentrate is 87.2% and the molybdenum grade is 55.8%; The amount of large water glass and the recovery rate of molybdenum decreased.

Figure 4 Selected water glass dosage test results

(3) Closed circuit test

On the basis of the conditional test and the optimal condition open circuit test, the closed circuit test was carried out according to the process structure and process conditions shown in Fig. 5. The test results are shown in Table 3.

Table 3 Closed-circuit test results (%)

In order to investigate the quality of molybdenum concentrate and the loss of molybdenum in tailings, chemical multi-element analysis was carried out on the closed-end final concentrate; the final tailings were screened and analyzed under microscope and see Table 4. It can be seen from Table 4 that the closed-circuit molybdenum concentrate has higher grades, and the content of impurities such as SiO ₂ , As, Sn, and Pb is in full compliance with the national quality standards for molybdenum concentrate. The tailings sieve water precipitation test and microscopic observation showed that the loss of molybdenum in the tailings was mainly in the -0.038mm grain size, and the molybdenum mineral particles were seriously polluted by the gangue, which reduced the hydrophobicity of the surface. It is difficult to recycle.

Figure 5 Closed-circuit test process and conditions

Table 4 Analysis results of main components of molybdenum concentrate (%)

Third, the conclusion

The ore is a single molybdenum ore, the metal mineral composition is simple, the harmful impurities are few, and the molybdenum is easily recovered by flotation. In the condition that the original ore contains 1.04% molybdenum and the grinding fineness is -200 mesh 90%, kerosene is used as the collector, 101 composite pine oil is used as the foaming agent, and an appropriate amount of water glass anti-floc dispersed sludge is added. A rough selection, two sweeps, three selections, closed-circuit process test obtained a technical index of 51.68% molybdenum concentrate and 96.40% molybdenum recovery rate. The process flow recommended by this test is reasonable in structure, simple in pharmaceutical system, and easy to industrialize.