Experimental study on recovery of lead and zinc from a tailings mine in Yunnan border

Yunnan is located in the southwestern border of China, bordering Vietnam, Myanmar and other countries, with a border line of thousands of kilometers. In the border area between China's Yunnan Ruili and Myanmar, there are a large number of tailings from previous mineral processing , which are various in nature and complex in nature. These large stockpiles of tailings not only occupy the land and forests, but because of their finer grain size, the winds in Yunnan are large, and the wind blows, causing more serious environmental pollution. Due to past ore processing techniques or other reasons, there are often a large number of useful elements in these tailings. For example, the minerals we studied, the sum of lead and zinc content exceeds 30%, according to preliminary estimates of lead and zinc. metal reached a total of 800 000 t, the equivalent of a small and Zinc Mine. Therefore, if these discarded tailings can be utilized, it will not only greatly reduce environmental pollution, but also turn waste into treasure, which has important practical significance for the comprehensive utilization of secondary resources and the implementation of sustainable development.

First, the nature of the ore

This is a kind of beneficiation tailings sample, the ore size is fine, and the -74μm particle size reaches 72.63%. The mineral material is partially agglomerated, and the moisture content is high, about 12%, and has a slight scent of mineral processing agent.

X-ray diffraction analysis showed that the main metallic ore minerals are sphalerite, galena, pyrite, alumina, lead, brass ore, limonite; non-metallic minerals are quartz, feldspar, chalcedony Wait. The results of multi-element analysis and phase analysis performed on them are shown in Tables 1 and 3, respectively.

Table 1 Multi-element analysis results of ore /%

Table 2 Lead phase analysis results /%

Table 3 Zinc phase analysis results /%

It can be seen from Table 1 that when processing the mineral material, lead and zinc in the mineral material should be mainly recovered, and the copper content is low, which may not be considered. From the results of phase analysis, the ore sample is a very special mineral sample. The zinc in the ore sample is mainly sulfide ore, while the lead mineral is mainly oxidized ore, and the oxidation rate is as high as 85%. Lead sulfate is the main mineral in spring.

Second, the process development

As a conventional sorting process for lead-zinc ore, there are mainly priority flotation and mixed flotation re-separation processes. However, as the mineral material for this treatment, zinc is mainly zinc sulfide, and lead is mainly lead oxide, and its floatability difference is relatively large. Therefore, the selection process of preferentially selecting zinc and then selecting lead oxide is adopted. When zinc flotation, added weight of chromium potassium sulfate was added and the inhibition of galena were activated zinc closed test conditions. The conventional sodium sulfide method is used for the flotation of lead oxide ore, but the test results are not satisfactory. The main performances are as follows: (1) The pH of the pulp is 5.5-6.2, even after adding lime (or sodium hydroxide), even if The amount of lime reached 10kg/t, and the pH of the pulp was still around 6. (2) The lead content in zinc concentrate is high. Although the zinc grade in zinc concentrate is higher, up to 52%, and the recovery rate is 91%, but the lead content is also as high as 11%, and lead and zinc contain each other seriously. (3) The lead recovery rate in lead concentrate is low, and the tailings contain high lead, which is almost equal to the lead content in the raw materials. (4) The amount of zinc inhibitor is large. Due to the high zinc content in the raw materials, the amount of zinc inhibitors is large and the production cost is high.

Based on the test results, it can be speculated that there may be some alkali-consuming compound, that is, an acidic substance, in the raw material. The natural floatability of some lead and zinc in raw materials is very good, and a large amount of lead oxide is difficult to be activated by sodium sulfide, and the flotation effect is poor. To this end, we have determined that the float-and-weight combination process is used to rapidly float lead and zinc in a weakly acidic medium, and then copper sulfate activates the flotation of zinc. The flotation tailings are re-selected (shaker) to enrich the lead oxide. The process flow is shown in Figure 1, and the experimental study is carried out in this process.

Figure 1 Flotation - re-election joint process

Third, the test results and discussion

According to the nature of the mineral material and preliminary test results, the selection process shown in Figure 1 is formulated, which is basically divided into four sorting circuits: lead-zinc and other floatable circuits, lead and zinc separation flotation circuits, zinc flotation circuits, and heavy Select the loop.

In floatable circuits such as lead and zinc, the objects recovered are some excellent floatable minerals, mainly galena and some sphalerite. In this circuit, generally do not use any activator and inhibitor of minerals. Under the action of common collectors , it requires galena to be recycled into the foam product as much as possible. The less the amount of zinc floating, the better. It can create better conditions for subsequent lead-zinc separation. After the conditions of grinding fineness, pulp pH value and collector dosage were tested, the best working parameters were determined. The grinding fineness was -74μm87.5%, the pulp pH was 6～6.5, and the ethyl yellow medicinal The amount is 70g/t. The flotation time is particularly important because, even under the same process parameters described above, the longer the flotation time, the higher the floating rate of zinc. Figure 2 shows the relationship between the flotation time and the sorting effect in this loop. In the first 3 minutes, the lead sulfide minerals floated quickly, the zinc minerals were relatively less floating, and the yield of coarse concentrates was not large. However, after 3 minutes, the yield of coarse concentrate increased significantly, mainly because zinc minerals began to rise a lot, and the zinc grade and work recovery rate increased rapidly, which is not needed because it will increase the subsequent lead-zinc separation. Difficulties, even if you can not get qualified lead concentrate, the loss of zinc will be greater. Therefore, the key to this operation is to control the flotation time and dosage, and perform fast flotation. 3min is recommended.

Figure 2 Relationship between flotation time and selection indicators

1—lead grade; 2—zinc grade; 3—lead recovery rate; 4-zinc recovery rate

Figure 3 Effect of separation of crude selective inhibitor on separation efficiency

1—lead grade; 2—zinc grade; 3—lead recovery rate

In the flotation circuit of lead-zinc separation, although the grades of lead and zinc in the processed coarse concentrate are relatively high, due to the small amount of minerals, the consumption of chemicals is not large, and the operating parameters (such as inhibition time) are more easily controlled.

In order to effectively separate lead and zinc minerals, tests were conducted on separate and mixed drug trials of zinc mineral inhibitors such as sodium sulfide, sodium sulfite, zinc sulfate, and sodium thiosulfate without using a collector. Results The effect of zinc sulfate and sodium sulfite in inhibiting zinc minerals was significant. The ratio of the two was 2:1. The dosage of lead and zinc was 400g/t and 200g/t, respectively. When the dosage of the inhibitor is doubled, the lead concentrate with lead content of 25.18%, zinc content of 2.17% and lead operation recovery rate of 85.32% can be obtained. When zinc sulphate is mixed with sodium sulfite, the relationship between the amount of different inhibitors and the lead and zinc grades in lead concentrate is shown in Fig. 3. The mechanism of inhibiting sphalerite can be considered as that the ZnO _{2 2} ^- colloid adsorbs on the surface of the sphalerite to enhance the hydrophilicity and the SO ₃ ^2- hydrolyzed precipitates Pb ²⁺ , so that the sphalerite loses its activation and combines to inhibit the sphalerite. .

In the zinc beneficiation circuit, since most of the sulfide minerals of lead have been selected, the beneficiation at this time is equivalent to the treatment of single zinc minerals. Therefore, we mainly used copper sulphate as the activator and carried out the condition test. When the amount of copper sulphate was 200g/t, the recovery rate of zinc operation was 86.75% and the zinc grade was 53.17%.

The purpose of re-election is mainly to select lead sulfate minerals. Under the discriminating effect of the shaker, qualified lead concentrates can be obtained with a grade of 32.59% and an operation recovery rate of 62.37%.

According to the condition test results, a closed circuit test was carried out according to the process flow of Fig. 1, and the test results are shown in Table 4.

Table 4 Closed-circuit process test results /%

Fourth, the conclusion

(1) The ore is more complex in nature. Most of the lead minerals are lead sulfate. The lead oxidation rate is as high as 83%, while zinc is mostly sulfide, that is, closed zinc ore, and the vulcanization rate is 88%.

(2) Using the re-floating combined process, the oxidized sulfide minerals are separately treated, and the lead oxide concentrate, the lead sulfide concentrate and the zinc sulfide concentrate are selected, so that the total recovery rate of lead in the lead concentrate is 79.36%. The recovery of zinc in zinc concentrate is 87.85%.

(3) According to the characteristics of the tailings, the minerals have greater influence on each other. We have adopted a floatable process that reduces lead and zinc in the concentrate and reduces the amount of chemicals used.