Experimental study on beneficiation of a scheelite in Hunan

First, the nature of the ore

A scheelite ore in Hunan belongs to the porphyry scheelite with a small amount of cassiterite . Small number of metal sulfide minerals, but more types, there pyrite, marcasite, pyrrhotite and traces bismuthinite, sphalerite like. The size of the scheelite is fine and uneven, and the main particle size ranges from 0.01 to 0.08 mm, and the upper limit of the particle size is 0.3 mm. Gangue minerals are quartz, feldspar, biotite, muscovite, followed topaz, barite, garnet, apatite, tourmaline, fluorite, calcite and the like. The multi-element analysis and tungsten phase analysis results of the scheelite are shown in Table 1 and Table 2.

Table 1 Results of multi-element analysis of raw ore ∕%

Table 2 Analysis results of tungsten ore phase of ore

It can be seen from Tables 1 and 2 that the recoverable valuable element is tungsten, and the occupancy rate of scheelite is 94.05%.

It has been identified that scheelite is mainly distributed in semi-automorphic grains, irregular granular single or few particles in the ore gap, or in the edge of biotite and cleavage gap.

Second, mineral processing test research

(1) Determination of the beneficiation process

Since the main recovered mineral scheelite has a finer grain size, it should be recovered by flotation process, and the ore contains a certain amount of sulfide ore, which will affect the final sulphur concentrate grade. Therefore, it should be removed before tungsten is selected. In addition to sulfide ore. According to the exploration test and the conditional test, the process flow of “preferred sulphur-white tungsten at room temperature rough selection-tungsten coarse concentrate heating selection” was determined.

(2) Influence of grinding fineness

The grinding fineness test procedure is shown in Figure 1, and the results are shown in Figure 2. It can be seen from the test results in Fig. 2 that as the fineness of the grinding increases, the WO ₃ content of the coarse concentrate decreases, and the recovery rate of WO ₃ increases. Considering the grinding cost and the difficulty in industrial realization, the grinding fineness is selected to be -200 mesh and account for 72%.

Fig.1 Principle flow of priority flotation-white tungsten normal temperature rough selection test

Figure 2 Grinding fineness test results

(3) Selection of collector types

At present, there are many types of collectors for scheelite flotation, so four common collectors were selected for testing. The test principle process is shown in Figure 1, and the results are shown in Table 3. It can be seen from Table 3 that GYR is used as the tungsten collector, and the crude concentrate (WO ₃ ) grade and recovery rate are relatively good.

(4) Test of rough selection conditions of white tungsten at room temperature

1. Effect of adjusting agent Na ₂ CO ₃ dosage

Na ₂ CO ₃ can adjust the alkalinity of the slurry, change the surface activity of the scheelite, and adjust the viscosity of the slurry and disperse the slime. The principle flow of the Na ₂ CO ₃ dosage test is shown in Figure 1. The test results are shown in Figure 3. It can be seen from Fig. 3 that as the amount of Na ₂ CO ₃ increases, the grade of WO _{3 in} tungsten concentrate increases, and the recovery rate decreases. For comprehensive consideration, the amount of Na ₂ CO ₃ is selected to be 1000 g ∕t.

Figure 3 Effect of regulator Na ₂ CO ₃ dosage

2, the effect of adjusting agent water glass

Water glass (Na ₂ SiO ₃ ) has a great influence on the flotation of scheelite, because it inhibits calcium-containing minerals such as fluorite, calcite and scheelite. When the dosage is small, the gangue minerals cannot be effectively inhibited, and the crude concentrate contains a low amount of WO ₃ ; when the amount is large, the scheelite is inhibited and the tungsten recovery rate is low. The principle flow of the water glass (Na ₂ SiO ₃ ) dosage test is shown in Figure 1. The test results are shown in Figure 4. It can be seen from the results of Fig. 4 that as the amount of water glass increases, the grade of tungsten concentrate increases, but the recovery rate decreases. Considering comprehensively, the amount of Na ₂ SiO ₃ is selected to be 1000 g ∕t.

Figure 4 Water glass dosage test results

Table 3 Comparison results of collectors

3. Influence of collector GYR dosage

The principle flow of GYR dosage test is shown in Figure 1, and the results are shown in Figure 5. As can be seen from Fig. 5, as the amount of the collector increases, the recovery rate increases, but the grade of the tungsten concentrate decreases. Considering comprehensively, the coarse selection of GYR is 300g∕t.

Figure 5 GYR dosage test results

(V) Influence of the selection of water glass for tungsten coarse concentrate

The selection of white tungsten coarse concentrate is the key to white tungsten flotation. At present, there are two kinds of selection processes for white tungsten coarse concentrate at home and abroad, namely, heating selection method and normal temperature selection method. The heating selection method is widely used because of the easy control of production and the stable quality of tungsten concentrate. When heating is selected, the white tungsten coarse concentrate is generally concentrated to a concentration of about 50%, stirred with water glass (Na ₂ SiO ₃ ), heated to 90 ° C, kept for 1 h, and then diluted to a concentration of about 20% for selection. . The amount of water glass (Na ₂ SiO ₃ ) is an important factor affecting the selected index. The test results are shown in Table 4. As can be seen from Table 4, as the amount of water glass (Na ₂ SiO ₃ ) increases, the grade of tungsten concentrate (WO ₃ ) shows an upward trend, but the recovery rate gradually decreases. Considering comprehensively, the amount of Na ₂ SiO ₃ is selected to be 1000 g ∕t.

Table 4 Test results of heating selected Na ₂ SiO ₃

(6) Closed-circuit test of the whole process of the sulphur ore beneficiation process

The process and conditions of the scheelite flotation closed circuit test are shown in Figure 6. The test results are shown in Table 5.

Figure 6 Process flow of scheelite flotation closed circuit test

Table 5 Full-process test results of scheelite ore selection

Third, the conclusion

(1) The tungsten ore is a porphyry scheelite deposit accompanied by a small amount of cassiterite. The amount of metal sulfides is small, but there are many types, such as pyrite, ferrous iron, pyrrhotite, and trace amounts of stibnite and sphalerite. The gangue minerals are mainly quartz, feldspar, biotite, muscovite, topaz, barite, garnet, apatite, tourmaline, fluorite, calcite and the like. The crystallite size of the scheelite is between 0.01 and 0.3 mm. The main recovered mineral in the ore is scheelite, which has less useful minerals and no recovery value.

(2) Adopting the process of “preferred sulphur-white tungsten at room temperature rough selection-coarse concentrate heating and heating selection”, for the ore containing WO ₃ 0.41%, the scheelite concentrate contains WO ₃ 66.20%, recovery rate 81. 27% of the technical indicators, so that tungsten has been better recovered.

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