Study on Cyanide-free Separation Process of a Low Grade Lead-Zinc Mine

Lead-zinc flotation separation process to more flotation applications, because of its simple configuration process, the drug does not require removal operation, mainly for simple component material ore, coarse-grained mineral disseminated ore more suitable in small lead and zinc mineral processing plant. Because cyanide is seriously polluted by the environment and will dissolve gold and silver , most of them now use cyanide-free inhibitors to suppress zinc and lead. Among the cyanide-free inhibitors, the combination of ZnSO ₄ and Na ₂ S0 ₃ is widely used, but the dosage of the agent is large and the cost is high. Because lime is cheap and easy to obtain, and studies have shown that when the free CaO concentration in the slurry is above 1000g/m ³ , it can inhibit sphalerite. For example, China's factory dam lead-zinc ore dressing plant only uses single lime to suppress sphalerite. Flotation galena has achieved good results. Therefore, this study attempts to use a single lime method and ZnS0 ₄ and Na ₂ S0 ₃ combination method for zinc-suppressed lead-lead comparison test, the results show that the single lime method has better mineral processing index than ZnS0 ₄ and Na ₂ S0 ₃ combination method. .

First, the nature of the ore

(1) Mineral content of ore

Metallic minerals in the ore to galena, sphalerite mainly containing a small amount of pyrite, magnetite, trace brass ore, hematite, blue copper minerals. The gangue minerals are mainly tremolite , diopside and epidote, followed by quartz and actinolite and contain a small amount of calcite and chlorite. The results of multi-element analysis of raw ore are shown in Table 1.

Table 1 Multi-element chemical analysis results of ore

Note: *The unit is 10 ^-6 .

(II) Analysis of the original mineral phase

The results of lead-zinc phase analysis show that lead-zinc is mainly sulfide ore, and it belongs to the type of lead-zinc ore according to the ore classification standard. The lead phase and zinc phase analysis results are shown in Table 2 and Table 3, respectively.

Table 2 Lead phase analysis results%

Table 3 % of zinc phase analysis results

(3) Main mineral inlay characteristics

The galena is mostly in the form of a grain-like structure, and the sphalerite has a grain-like structure. The two are intertwined with veins, and sometimes the two are dispersed into veins or scattered, and the relationship is relatively close. Galena is often interspersed with gangue minerals, some of which are illusory minerals, and some contain gangue minerals such as diopside, tremolite, and epidote. Part of the galena is replaced, wrapped in magnetite or interspersed in pyrite, or coated with pyrite particles to form a metamorphic structure or inclusion structure. A small number of sphalerite crystals are distributed in chalcopyrite emulsions to form an opalescent structure; some sphalerites encapsulate pyrite particles, consisting of structures, and sphalerite interspersed with gangue minerals. The particle sizes of galena and sphalerite are mainly medium and fine particles (0.04~0.5mm), accounting for 62% and 69% respectively. Judging from the output of galena and sphalerite, the type of inlay is mainly composed of equal granular structure, uneven granules, and unequal veins. The former mainly occurs in the ore of the sparsely disseminated structure, and the latter is composed of the fine vein-disseminated ore.

Second, lead and zinc cyanide separation process selection

(1) Process plan selection

According to the ore properties of the ore, it is known that the main minerals of the ore are the lead, zinc and silver. From the state of occurrence of silver and the amount of silver in lead concentrate, silver can be enriched as lead is enriched. It can be seen that the ore recovery of the ore should be mainly lead and zinc sulfide. The size of the galena and sphalerite in the ore is mainly medium and fine, followed by fine particles. The floatability of galena is generally better than that of sphalerite, and it is difficult to activate after the galena is suppressed. In addition, in the lead-zinc polymetallic sulfide ore, the lead content is less than that of zinc. Therefore, for the nature of the ore, it is advisable to use the preferential flotation principle process of “Zinc-Suppressing Lead” for separation of lead and zinc flotation.

(2) Choice of pharmaceutical system

The most commonly used collectors for flotation galena are xanthate and black medicine. The optimum pH for flotation galena is 7-8. At the same time, xanthate and black medicine are also collectors of sphalerite. Ethyl sulfide is a widely used sulfide ore collector, which is second only to xanthate and black medicine. It has good selectivity and traction for lead. The optimum pH value for flotation minerals is higher than that of xanthate and black medicine. (pH value is 9.0-9.5), the selectivity is stronger than that of xanthate, and the attraction of pyrite in weak alkaline medium is particularly weak, and the dosage is only 1/2 to 1/5 of the xanthate.

This experiment will use the "ZnS0 ₄ + Na ₂ S0 ₃ combination zinc suppression, ethyl xanthate or butyl ammonium black medicine float lead" and "single CaO zinc, ethyl sulphide floatation" two non-cyanide agent system Comparative experimental study.

(3) Grinding fineness selection

The test was carried out under laboratory conditions, and the sample was mixed and crushed, and then bagged. The unit sample weighed 500 g. Grinding fineness adopts one-step rough selection and one sweeping of lead circuit, one rough selection and one sweeping process of zinc circuit, wherein the combined inhibitor ZnS0 ₄ + Na ₂ S0 _{3 is} added to the grinding machine at a dosage of 750g/t, lead. Rough selection of ethyl xanthate 150g / t, pine alcohol oil 26g / t, lead sweeping inhibitor ZnS0 ₄ + Na ₂ S0 ₃ each 300g / t, pine oil 13g / t, zinc rough selection CaO 1000g / t, CuS0 ₄ 500g / t, butyl xanthate 60g / t, pine oil 13g / t, zinc sweep CuS0 ₄ 400g / t, butyl xanthate 30g / t, pine oil 13g / t, the test results are shown in Figure 1. The test shows that with the increase of grinding fineness, the content of lead and zinc in tailings also gradually decreases, and the recovery rate of lead gradually increases. The recovery rate of zinc slows down after the fineness of grinding reaches -74μm and accounts for 60%. The grade of lead and zinc decreased significantly with the increase of grinding fineness. It can be seen that the fineness of grinding is -74μm, accounting for 70%, and the comprehensive index of lead and zinc is the best.

Study on Separation Process of Zinc-Suppressing and Floating Lead by ZnS0 ₄ +Na ₂ S0 ₃ Combination

(1) Test of the amount of crude selective inhibitor for lead-zinc separation circuit

Inhibitor dosage test adopts a rough selection process, in which the combined inhibitor is added to the grinding machine, the dosage of the agent: lead crude selection of ethyl xanthate 150g / t, pine alcohol oil 26g / t, the test results are shown in Figure 2.

The results show that with the increase of the amount of inhibitor, the content of zinc in lead crude concentrate gradually decreases, but when the amount of ZnS0 ₄ +Na ₂ S0 ₃ reaches 750+750g/t, the amount is increased. Too obvious, but increased the cost of mineral processing. The final choice of ZnS0 ₄ + Na ₂ S0 ₃ is 750 + 750 g / t.

(II) Tests on the types and dosages of coarsely selected collectors for lead and zinc separation circuits

The lead crude selection collector was selected according to the dosage of ethyl xanthate and butyl according to the black drug. The test used one rough selection, two sweeps, and one selection process. The dosage of the agent: ZnS0 ₄ and Na ₂ S0 ₃ lead were coarse. Each of the selected 750g / t, lead right selection I each 300g / t, lead sweep selection II each 150g / t; pine oil oil lead selection 26g / t, lead sweep selection 13g / t. The test results are shown in Figures 3 and 4, respectively. It can be seen from Fig. 3 that as the amount of ethyl yellow is increased, the recovery rate of lead is correspondingly increased, but the grade of lead is decreasing, and the content of zinc in lead concentrate is increasing. Therefore, the difficulty of separating lead and zinc is increased, so the amount of ethyl yellow is preferably 150 g/t. As can be seen from Fig. 4, a good indicator can also be obtained by using a butyl black drug as a lead collector, and the amount thereof is preferably 30 g/t. However, the amount of butyl used in black medicine has a greater influence on the grade of lead, and the stability is poor. Comprehensive consideration, the final choice of ethyl xanthate as the collector of the pharmaceutical system, the amount of 150g / t.

(3) Open circuit test

The open circuit test uses a lead circuit for one rough selection, two selections, two sweeps, one zinc rough selection, two selections, and two sweeping processes. The test results are shown in Table 4.

Table 4 Open circuit test results%

(4) Closed circuit test

On the basis of the open circuit test, a closed circuit test was carried out, and the test indicators are shown in Table 5.

Table 5 % of closed circuit test results

Study on Separation Process of Single Lime and Zinc-Silver Lead

(1) Trial of lead and zinc separation crude selection inhibitor

The lead crude selection inhibitor dosage test uses a rough selection process, in which the inhibitor CaO is added to the grinding machine, and the dosage of the agent: lead crude sulfur sulphide 40 g/t, pine alcohol oil 26 g/t, the test results are shown in Fig. 5. . The test results show that with the increase of CaO dosage, the grade of lead crude concentrate gradually increases, but the recovery rate is gradually decreasing. Finally, the CaO dosage is 2000g/t.

(II) Trial of lead and zinc separation and coarse selection of collectors

The lead coarse selection collector dosage test uses a rough selection, two sweeps, and a selection process. The inhibitor CaO is added to the grinding machine. The dosage of the agent is CaO 2000g/t, and the sulfur trichloride lead is selected 2.5g/ t, pine oil lead was roughly selected 26g / t, the test results are shown in Figure 6. The test results show that only a single CaO is used as an inhibitor of zinc with ethyl sulphide, and high-quality lead concentrate can be obtained with high recovery rate, and the dosage of the agent is only 40g/t, which is less than ethyl. The amount of yellow drug is 1/3 of 150 g/t.

(3) Open the road to test the face

The open circuit test uses a lead circuit for one rough selection, two selections, two sweeps, one zinc rough selection, two selections, and two sweeping processes. The test results are shown in Table 6.

Table 6 Open circuit process test results%

(4) Closed circuit test

On the basis of the open circuit test, a closed circuit test was carried out. The closed circuit test flow is shown in Figure 7, and the test indicators are shown in Table 7.

Table 7 % of closed circuit test results

V. Conclusion

(1) The metal minerals in the mine are mainly galena and sphalerite.

Silver is mainly found in galena, and the main elements recovered are lead, zinc and silver. The lead grade of raw ore is 1.89% and the grade of zinc is 2.01%, of which lead sulfide accounts for 79.89% and zinc sulfide accounts for 75.97%.

(2) The experiment uses the "ZnS0 ₄ + Na ₂ S0 ₃ combination zinc suppression, ethyl xanthate float lead" olive-free pharmaceutical system, obtaining lead concentrate grade 57.82%, lead recovery rate of 80.12%, zinc concentrate grade 46.70 %, zinc recovery rate was 64.12%; using the "single lime method to inhibit zinc, ethyl sulphide and lead sulphide" without the atmosphere of the drug system, the lead concentrate grade 62.78%, lead recovery rate of 80.13%, zinc concentrate grade 47.82% The zinc recovery rate is 67.85%. One or two cyanide-free pharmaceutical systems can obtain better beneficiation indicators.

(3) The "single lime method" not only has the advantages of smaller dosage and lower cost than the "ZnS0 ₄ + Na ₂ S0 ₃ combination method", but also improves the lead concentrate grade by nearly 5% under the same lead recovery rate. In the case of similar zinc concentrate grades, zinc recovery rate increased by nearly 4%.

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