A large mine tungsten containing about 0.44% WO _3, scheelite and wolframite 6.5:3.5 ratio, using the first flotation recovery scheelite, wolframite its flotation tailings. Due to the low tungsten grade of the white tungsten flotation tailings, the direct flotation of the wolframite is not satisfactory. Therefore, improving the selection of black tungsten flotation is the key to improving the black tungsten flotation index.

First, the nature of the ore

The ore skarn plurality of metal ore, the primary metal minerals scheelite, wolframite, bismuthinite, molybdenite, followed by natural bismuth, tungsten China, pyrrhotite, pyrite, copper ore, magnetite, cassiterite, hematite, a small amount of iron Qin, Qin calcium tin ore; fluorite main gangue minerals, followed by quartz, feldspar, andradite, white mica, black mica , a small amount of epidote, kaolinite, chlorite, wollastonite, pyrophyllite, apatite, zircon and the like. The multi-element analysis of raw ore is shown in Table 1. The metal distribution rates of WO ₃ in scheelite, wolframite and tungsten are 65.61%, 29.41% and 4.98%, respectively.

Second, experimental research and discussion

The laboratory test was carried out by SSS-I high-gradient magnetic separator developed by Guangzhou Nonferrous Metal Research Institute. The magnetic medium and pulsation impulse of high-gradient magnetic separator were studied in white tungsten flotation tailings respectively. Experiments were carried out under the condition of magnetic field strength, and the process of strong magnetic separation of scheelite recovered from white tungsten flotation tailings was studied.

Table 1 Multi-element analysis results of raw ore

(1) Selection of magnetic medium for high gradient magnetic separator

Choosing the rod diameter and height dimension of a suitable magnetic medium is one of the keys to achieving a good selection index. The test was carried out under the conditions of a magnetic separator pulsation 300 times/min, a stroke of 12 cm, and a magnetic field strength of 0.80T. The rod diameter φ2+1 mm of the magnetic medium was used, and the test was carried out under the conditions of the magnetic medium height of 10 cm and 14 cm respectively; the magnetic medium rod diameter φ2+1.5+1 mm and the magnetic medium height of 14 cm were used for the test. The test results are shown in Table 2.

Table 2 Test results of magnetic media

It can be seen from Table 2 that when the rod diameter of the magnetic medium is φ2+1mm, and the height of the magnetic medium is 14cm, a better sorting index is obtained under the condition of low magnetic field strength (0.48T); the rod diameter of the magnetic medium is φ2+1mm, and the magnetic The height of the medium is 10 cm. Under the condition of magnetic field strength of 0.48~0.61T, the selection index is second; the diameter of the magnetic medium is φ2+1.5+1mm, and the height of the magnetic medium is 14cm. Under the condition of magnetic field strength of 0.8T, The selection index is poor. Therefore, a magnetic medium having a rod diameter of φ2+1 mm and a height of 14 cm was finally selected.

(2) Influence of pulsating impulse change of high gradient magnetic separator on magnetic separation test results

The magnetic separator pulsation test was carried out under the conditions of a rod diameter φ2+1 mm of a magnetic medium, a magnetic medium height of 10 cm, a pulsation stroke of 12 cm, and a magnetic field strength of 0.8 T.

The influence curve of the high-gradation pulsation magnetic separator on the magnetic separation index is shown in Fig. 1. In the range of 200-300 times/min, it can be seen from Fig. 1. As the number of punches increases, the grade of black tungsten strong magnetic concentrate gradually increases, and the recovery rate gradually decreases.

(3) Influence of magnetic field strength on test results

The magnetic field strength test was carried out under the conditions of a rod diameter of the magnetic medium of φ2+1 mm, a magnetic medium height of 14 cm, a magnetic separator pulsation stroke of 300 times/min, and a stroke of 12 cm. The effect of magnetic field strength on the test indicators is shown in Figure 2.

Figure 1 Impact of the punching on the strong magnetic separation

Figure 2 Effect of magnetic field strength on strong magnetic separation

It can be seen from Fig. 2 that in the range of magnetic field strength 0.28~0.80T, with the increase of magnetic field strength, the recovery rate of black tungsten strong magnetic concentrate is gradually increased and the amplitude is larger; while in the range of 0.28~0.48T, black tungsten is strong. There is no change in the grade of magnetic concentrate; in the range of 0.48-0.8T, the grade of black tungsten strong magnetic concentrate has a decreasing trend. Therefore, it is appropriate to select a rough magnetic field strength of 0.48T.

(4) Research on the process of strong magnetic separation

Under the conditions of rod diameter φ2+1mm of magnetic medium, magnetic medium height of 14cm, magnetic separator pulsation times of 300 times/min and stroke of 12cm, the selection and sweeping processes were tested separately.

1. Research on selected process flow

The white tungsten flotation tailings were subjected to a rough selection, a rough selection, and a selective process flow for comparative tests. A rough selection process (Fig. 3): As the magnetic field strength changes, the curve of the strength and recovery of the strong magnetic concentrate is shown in Fig. 5. One rough selection and one selection process (Fig. 4): When the rough selected magnetic field strength is 0.80T, the variation curve of the grade and recovery rate of the black tungsten strong magnetic concentrate is shown with the change of the magnetic field strength of the strong magnetic selection. 5.

Figure 3 A rough magnetic separation process

Figure 4 A rough selection, a selection of strong magnetic separation process

Figure 5 Effect of selection times on strong magnetic separation

Using a rough selection (magnetic field strength 0.8T), a selective process flow, the selected magnetic field strength is the same as the rough selected magnetic field strength of a rough selection process, the grade of the black tungsten strong magnetic concentrate in a rough selection process And the recovery rate is higher. Therefore, the strong magnetic separation process is not suitable for use in selected operations.

2. Research on sweeping and selecting the art process

A rough selection and a second sweep (Fig. 6) comparison test were performed on the white tungsten flotation tailings. The magnetic field strength of sweeping one and sweeping two is 0.8T. With the change of the strength of the rough selected magnetic field, black tungsten strong magnetic coarse concentrate, black tungsten strong magnetic coarse concentrate + sweep-black tungsten strong magnetic concentrate and black tungsten strong magnetic coarse concentrate + sweep-black tungsten strong magnetic concentrate The recovery rate and grade change curve of the +sweeping black tungsten strong magnetic concentrate are shown in Fig. 7 and Fig. 8.

Figure 6 Process of rough selection and secondary sweep selection

Fig. 7 Effect of sweeping times on the recovery rate of black tungsten strong magnetic concentrate

Fig. 8 Effect of sweeping times on the grade of black tungsten strong magnetic concentrate

As can be seen from Fig. 7 and Fig. 8, the black tungsten strong magnetic concentrate obtained by one rough selection has a higher grade and a lower recovery rate. After one sweep, the recovery rate can be increased to a large extent, but the concentrate grade has decreased; after the second sweep, the recovery rate is small and the concentrate grade is not changed much. Therefore, it is more appropriate to adopt a rough selection and one sweeping process.

It is determined by experiments that the black tungsten tungsten magnetic separation of white tungsten flotation tailings should adopt a rough selection and one sweep selection process.

(5) Full process test results

Through small-scale experimental research, in the magnetic medium rod diameter φ2+lmm, magnetic medium height 14cm, magnetic separator pulsation stroke 300 times / min, stroke 12cm, a rough selection (0.48T), a sweep (0.8 T) Strong magnetic separation process (Figure 9), the test results are shown in Table 3.

Figure 9 A rough selection, one sweep and strong magnetic separation process

Table 3 Full process flow test results

It can be seen from Table 3 that the white tungsten flotation tailings (0.235% WO ₃ ) can obtain a black tungsten strong magnetic concentrate with a grade of 0.47% WO ₃ and a recovery rate of 90.64% after one rough selection and one sweep magnetic strength test.

Third, industrial test results

Industrial-scale tests conducted at 260t / d of ore dressing plant. Process: white tungsten flotation tailings obtained strong magnetic separation (primary rough selection, one sweep) to obtain black tungsten strong magnetic concentrate; 2 sets of high gradient magnetic separator, pulsating stroke 12cm, punching 200 times / min The rough selection and sweep magnetic field strength is 1.0T. The cumulative index of industrial tests for 12 classes in 4 consecutive days: 0.28% WO _{3 of} strong magnetic separation ore (ie white tungsten flotation tailings), after a rough selection and a sweep (Figure 9), the grade is 0.43%. WO ₃ . Black tungsten strong magnetic concentrate with an operating recovery rate of 73.26% (recovery of ore recovery of 29.36%).

Fourth, the conclusion

(1) According to the characteristics of weak magnetic properties of the black tungsten ore, the high-gradient magnetic separator is used to recover the black tungsten ore in the white tungsten flotation tailings, which can improve the selection of the candidate and reduce the processing capacity of the black tungsten flotation.

(2) Under the conditions of rod diameter φ2+lmm of magnetic medium, magnetic core height 14cm, magnetic separator pulsating stroke l0cm, punching 300 times/min, a rough selection and one sweeping process can be used to obtain better black tungsten. Strong magnetic concentrate selection index.

(3) Industrial test results show that the process is an effective method for pretreating low-grade wolframite.

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