Experimental study on dressing of a low grade tungsten-molybdenum ore

The main beneficiation method for recovering scheelite is flotation. In general, scheelite ore, which is dominated by silicate minerals or quartz , is easier to sort. When scheelite is symbiotic with one or more minerals such as carbonate minerals, fluorite , barite, etc., the flotation process is relatively difficult and complicated due to the similar floatability of the minerals. The white tungsten flotation process is generally divided into rough selection and selection. The rough selection aims to eliminate the gangue minerals, thereby increasing the ratio of coarse selection and enrichment. The selection is the key to obtaining qualified concentrates from the flotation of scheelite. The core is to strengthen the inhibition ability of gangue minerals. Commonly used processes are "Petrov method" and 731 oxidized paraffin soap at room temperature flotation.

A low-grade tungsten molybdenum metal skarn, mainly metallic minerals scheelite, molybdenite, the main gangue minerals garnet, diopside, quartz, potassium feldspar, carbonates. The raw ore WO ₃ grade is 0.26% and the molybdenum grade is 0.022%. In order to comprehensively recover tungsten and molybdenum, a detailed ore dressing test study was conducted on the mine.

According to the characteristics of the ore, the experimental study on the floating scheelite after the first sulphide ore is obtained. The process has obtained good technical indexes. The beneficiation index obtained by the closed circuit test is: tungsten grade 66.10%, tungsten recovery rate 86.74% tungsten Concentrate, molybdenum concentrate with 45.31% molybdenum grade and 65.78% molybdenum recovery.

First, the nature of the ore

(1) Analysis of main chemical components of ore and phase analysis

The analysis results of the main chemical components of the ore are shown in Table 1. The results of the tungsten phase analysis are shown in Table 2, and the results of the molybdenum phase analysis are shown in Table 3.

The analysis results show that the useful minerals are single, tungsten is mainly scheelite, and molybdenum is mainly molybdenite. Although the content of tungsten and molybdenum has reached the grade requirement of mining and recycling, it is low in the same type of ore. Other valuable elements did not meet the grade requirements for comprehensive recycling. Due to the low grade of molybdenum, it may affect the improvement of flotation recovery.

Table 1 Analysis results of main chemical components of ore

Table 2 Tungsten phase analysis results

Table 3 Results of molybdenum phase analysis

(2) Embedding characteristics of major minerals

Scheelite: The most important metal mineral in the ore, and the most important object of recycling. It is self-shaped in half self-shaped granular, granular, fine vein-like unevenly embedded, and the scheelite is mainly composed of fine particles. The particle size is mainly about 0.1 mm, and the individual coarse particles can reach 2 to 3 mm, and the garnet and diopside are contained therein.

Molybdenum ore: Molybdenum ore is one of the main useful minerals and is also the main recycling target. It is grayish white under the microscope and is distributed in the gangue with a particle size of 0.10-0.15 mm.

Pyrite: a semi-euhedral shape from a particulate a particle size of 0.03 ~ 0.15mm, disseminated sparsely distributed.

Pyrrhotite: pale yellow rose microscope, he mostly granular shape, a particle diameter of 0.03 ~ 0.20mm, often coexist with brass ore, distributed in a variety of ores.

Chalcopyrite: It is a brass color under the microscope. It is mostly a granular aggregate with a particle size of 0.05-0.21 mm. It often forms a co-edge structure with pyrrhotite and is sparsely disseminated in the gangue.

Garnet: The main gangue minerals can be divided into two types according to their structural characteristics. One is medium-grain-grained garnet, the particle size can reach 2~3mm, and the second is microscopically crystalline garnet. It is 0.05 to 0.10 mm, and all are homogeneous.

Diopside: The main gangue minerals can be divided into two groups according to the observation of the microscope. The first one is produced in the quartz horn rock. It has a granular shape with a particle size of 0.05-0.10 mm. The remaining layers are determined by the distribution of the bribes. The second is produced in garnet and diopside skarn, and the particle size is 0.1-0.5mm, which is associated with garnet.

Potash feldspar: gangue mineral, irregular, part of diopside, garnet or irregular veins, particle size of 0.1 ~ 0.5mm, mainly garnet, yellow brown under the lens, the surface is mostly clay Minerals are accounted for.

Quartz is mostly irregular granular, often interpreting early minerals or interspersed with other mineral particles, the particle size is different, and the shape is limited by spatial form.

Other minerals include epidote, zoisite, tremolite , plagioclase, etc., with a small content.

Second, mineral processing experimental research

(1) Process plan and process determination

The chemical analysis results of the samples show that the valuable elements in the ore are tungsten and molybdenum. Because the sample contains less sulfide minerals, the planktonicity of molybdenite is obviously superior to that of other sulfide minerals. The principle of re-grinding molybdenum from sulphide ore and then removing molybdenum from sulphide ore tailings. In order to enhance the selective flotation of scheelite and calcium-containing gangue minerals during flotation, it was determined that the lime method was used for sorting. That is, lime and sodium carbonate are used as adjusting agents, water glass is used as an inhibitor, and 731 oxidized paraffin soap is used as a collector .

(2) Grinding fineness test

The test is carried out under laboratory conditions. Laboratory equipment: XMQ240mm×90mm cone ball mill , XFD12 flotation machine, XFGII50 hanging tank flotation machine and XFGC-80 inflatable hanging tank flotation machine, water removal glass is industrial reagent In addition, other flotation reagents are chemically pure. The sample was mixed by grinding and sieving and then bagged. The unit sample weighed 1000g. Grinding fineness test adopts a rough selection and a sweeping process. The grinding fineness -74μm accounts for 80%, which is determined by the condition test.

(3) Molybdenum flotation test

It can be seen from the chemical multi-element analysis that the ore containing a small amount of molybdenum, copper and lead , the presence of these sulfide ore will cause some pollution to the subsequent flotation of tungsten, so a full float desulfurization test is required. Molybdenite roughing collector apolar and kerosene oil, sodium carbonate and sodium silicate modifier, test uses a roughing, scavenging two, then the test procedure is selected from a crude concentrate two-stage grinding. Among them, molybdenum was compared with the effect test of water glass + sodium sulfide and TGA sulfide ore inhibitors. It was found that TGA can effectively inhibit copper and sulfur in the process of molybdenum selection. It is a new type of environmentally friendly and safe beneficiation agent. The molybdenum selection test showed that when sodium sulfide was used as the selective inhibitor, not only the dosage was large, but also the inhibition effect was not good, while the TGA dosage was small, and the inhibition effect was very good, only 1/10 of the amount of sodium sulfide. Under the same conditions, when the water glass + sodium sulfide is 140+500g/t, the grade of molybdenum coarse concentrate is 15.94%, which is nearly doubled. After molybdenum selection for 6 times, a molybdenum concentrate containing 45.31% of molybdenum and a recovery rate of 65.78% can be obtained.

(4) White tungsten flotation test

1. Lime dosage test

Adding lime to the white tungsten rough selection, in addition to increasing the pH value, Ca ^{2 +} produced by lime dissolution is adsorbed on the surface of gangue such as calcite , fluorite, quartz, etc., and CaCO is formed on the surface of these gangue after adding sodium carbonate. ₃ precipitation, the gangue is thus suppressed, so that white tungsten preferentially floats out. The results of the lime dosage test are shown in Table 4.

Table 4 Lime dosage test results

The addition of the gangue inhibitor lime has the effect of selectively inhibiting the gangue. As the amount of lime increases, the tungsten grade also increases. When the amount of lime is 300-500 g/t, the tungsten index is better.

2, sodium carbonate dosage test

The problem of white tungsten flotation is the separation of white tungsten and calcium-containing minerals with similar floatability. The correct choice of regulators and inhibitors is the key. In the rough selection operation, sodium carbonate is used as a pH adjuster, and water glass is used as a gangue inhibitor to obtain a certain degree of enrichment of scheelite.

Using sodium carbonate as a pH adjuster, in addition to forming an alkaline medium in which scheelite is easy to float, it can also precipitate Ca ^{2 +} , Mg ^{2 +} and various heavy metal ions in the slurry to overcome the adverse effects of these ions on flotation in water. In the presence of water glass, when the pH is 7 to 10, calcite is strongly suppressed, and fluorite is also well suppressed. Therefore, sodium carbonate is suitable for flotation of skarn-type scheelite containing more calcite. The test results of sodium carbonate dosage are shown in Table 5.

Table 5 Test results of sodium carbonate dosage

According to the test results, as the amount of sodium carbonate increases, the yield of tungsten concentrate increases, and the grade and recovery rate increase first and then decrease. When the amount of sodium carbonate is 2000g/t, the tungsten index reaches the optimum value. The increase in the indicator is reduced.

3, water glass dosage test

Water glass is the most commonly used dispersant and gangue inhibitor in flotation of tungsten. The dispersion and inhibition of water glass is generally considered to be due to the hydrophilicity of HSiO ₃ ^- and water glass colloid particles adsorbed on the mineral surface to make the mineral hydrophilic. However, it is inhibited, and the adsorption of the negatively charged glass colloidal particles adsorbed on the surface of the mineral to make the mineral hydrophilic and inhibited, and the ore particles adsorbed with the negatively charged glass colloidal particles repel each other and act as a dispersion. The test results of water glass dosage are shown in Table 6.

Table 6 Water glass dosage test results

It can be seen from the test results that with the increase of the amount of water glass, the grade of tungsten concentrate also increases, reaching 1500g/t, and the recovery rate of tungsten concentrate is obviously reduced. Therefore, the index of water glass is better at 700g/t. .

4, collector 731

At present, most of the collectors used in the flotation of scheelite in China are mainly 731 oxide paraffin soap. It is generally believed that there is a synergistic effect when sodium carbonate is shared with water glass. By controlling the pH value of the slurry, the HSiO ₃ ^- in the slurry is maintained in a concentration range favorable for strengthening inhibition, and is matched with a highly selective 731 oxidized paraffin soap. The scheelite collector is used to achieve a higher coarse enrichment ratio. Through experimental research, it can be seen that the index of white tungsten flotation reaches the optimum value when the amount of 731 is 700g/t.

5, white tungsten selection test

The test of the white tungsten coarse concentrate at room temperature selection and heating selection shows that for the ore, a qualified concentrate with high tungsten recovery rate can be obtained at room temperature. Under the conditions of other conditions, the tungsten concentrate grade after heating selection was 71.60%, and the recovery rate of the selected section was 46.23%. The tungsten concentrate grade after room temperature flotation is 69.58%, and the recovery rate of the selected section is 54.63%. By comparison, we choose the normal temperature selection.

The white tungsten at room temperature is selected under the condition of adding appropriate water glass. After being stirred for a long time (greater than 30 minutes), the adsorbent adsorbed on the surface of the gangue mineral is analyzed and suppressed, and the white tungsten is still floatable. The method eliminates the inconvenience of high temperature and high concentration, and also saves the cost of mineral processing.

6, the test process

Through the above conditions test, a rough selection, two sweeps, and six selections are used for the sulfide ore. One selection, two sweeps, and five selected flotation normal temperature open-circuit test procedures are applied to the scheelite. See Table 7.

Table 7 Normal temperature open circuit test results

The normal temperature open-circuit process test can obtain a molybdenum concentrate with a molybdenum concentrate grade of 46.02% and a recovery rate of 21.42%, and a tungsten concentrate with a tungsten concentrate grade of 69.58% and a recovery rate of 54.63% can be obtained. Due to the low content of molybdenum in the ore, it is the main reason for the low recovery rate of molybdenum.

On the basis of the open-circuit process test, the normal temperature closed-circuit process test was carried out. The closed-circuit process is shown in Figure 1, and the test indicators are shown in Table 8.

Figure 1 Normal temperature closed circuit test procedure

Table 8 Normal temperature closed circuit process test results

Third, the conclusion

(1) The metal minerals mainly recovered by the mine are scheelite and molybdenum ore, and a small amount of pyrrhotite, pyrite, chalcopyrite, etc., which does not have the value of recycling. The ore has a tungsten grade of 0.26% and a molybdenum grade of 0.022%, which is a skarn type ore.

(2) Before the flotation of scheelite, the sulfide ore is floated first, and the obtained crude concentrate is re-elected twice. The closed-circuit test has a good index of 45.31% of molybdenum concentrate grade and 65.78% recovery rate.

(3) The experiment uses lime method to float scheelite, and adding lime can better inhibit calcium-containing gangue minerals such as calcite and fluorite.

(4) The normal temperature flotation of white tungsten is carried out by one rough selection, two selections, two sweeps, and the process of refining and refining the coarse concentrate at room temperature. The group road test has a tungsten concentrate grade of 66.10% and a recovery rate of 86.74%. Good indicator.

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