Fankou lead zinc mine tailings No. l production from 1968 to the early 1980s, closed libraries, tailings storage capacity area 20hm 2, a total of tailings 400,000 t. Today, with the depletion of ore, the depletion of resources and the increasing environmental awareness, the comprehensive utilization of tailings will become an inevitable choice for the sustainable development of Fankou lead-zinc mine.
Due to the influence of technical level, equipment performance, economic conditions and other factors, the mineral processing process and ore dressing level of Fankou Lead-Zinc Mine in the 1960s and 1970s were limited, and the recovery rate of valuable elements such as lead, zinc and sulfur was not high. A considerable part of the valuable elements are lost to the tailings. Acidification of mine tailings is a relatively common phenomenon, and some tailings have the potential to produce acid, especially tailings with higher sulfur content. The sulfur content in the tailings of No. 1 tailings pond of Fankou Lead-Zinc Mine is as high as 13.8%, and sulfur is mainly in the form of pyrite . 20 years, because pyrite ore tailings surface is exposed to air, coupled with the natural leaching, pyrite bacteria catalyzed reaction with water and oxygen, produces a greater amount of sulfuric acid, the tail No. 1 natural pH value of the ore dropped 6.5 libraries, and to promote the dissolution of cadmium lead and zinc tailings surface portion of the heavy metals. The study also found that acidification mainly occurs in the surface layer of tailings from 0 to 30 cm, which has little effect on the bottom layer. However, once acidification occurs, the pH value will decrease rapidly, and the dissolution of heavy metal ions will increase remarkably. A series of reactions will occur with acidification. The pollution of the tailings to the environment. Therefore, the recovery of the sulfur concentrate in the No. 1 tailings pond of Fankou Lead-Zinc Mine can greatly reduce the sulfur content, reduce acidification, protect the environment, and increase the economic and social benefits of the enterprise.
First, tailings properties
The chemical composition and particle size distribution of the main elements of the tailings of No. 1 tailings mine of Fankou Lead-Zinc Mine are shown in Table 1 and Table 2, respectively.
It is seen from Table l and Table 2, No. 1 Fankou tailings tailings in the main component of quartz, carbonate minerals, sericite gangue, followed by the metal content of sulfur and iron, lead, zinc, etc. It is also higher, in which sulfur and iron are mainly present in the form of pyrite, and the content of pyrite in the entire tailings is as high as 18%. The tailings have a coarser particle size, with a content of +0.074 mm and a content of about 70%, and a content of -0.037 mm of less than 15%. The sulfur content of the -0.074 mm grain tailings is only 3.85%, and most of them are sphalerite and galena, and the sulfur content of the tailings of +0.074 mm rises to 15.2%. According to the further analysis of the relationship between particle size and dissociation degree of Fankou lead-zinc ore, it can be seen that when the ore is ground to -0.074mm, the disintegration of pyrite is relatively sufficient. When the ore is ground to -0.037mm, the galena and flash The zinc mine was fully dissociated. In the original ore flotation process, -0.074mm pyrite, -0.037mm sphalerite and galena were adequately dissociated, and were basically recovered at that time. The pyrite in the tailings was mainly concentrated. In the +0.074 mm size range. Because of pyrite, galena, sphalerite density separator is the other 0 5.0 ~ 5.2t / m 3, 6.5 ~ 7.0t / m 3, 4.0 ~ 4.2t / m 3 The density of gangue (quartz, carbonate minerals, sericite, etc.) is 2.6-2.9t/m 3 , and the valuable elements such as lead, zinc and sulfur have a large difference with the density of gangue minerals, which is more suitable for re-election. Perform preliminary separation and enrichment. Therefore, it is determined that the tailings of the No. 1 tailings pond of Fankou Lead-Zinc Mine should be classified by fine-graining of 0.074 mm, wet-grinding of some heavy ore in the sieve, and recovery of sulfur concentrate by combined flotation and partial flotation. .
Second, the test results and analysis
(1) Re-election test
Due to the lower grade of valuable metals in the tailings of No. 1 tailings mine of Fankou Lead-Zinc Mine, the content of gangue (quartz, carbonate minerals, sericite, etc.) reached 70%. The cost of a single flotation recovery valuable element is high, and it is difficult to obtain qualified concentrate products. All the tailings will be greatly increased by the grinding, and the finer tailings will also be muddy. The recovery of metal elements such as mines and lead and zinc is unfavorable. Re-election without chemicals, no pollution to the environment, the water source can recycle the external drainage of the adjacent No. 3 tailings pond, and the equipment is simple and low cost, which is the first choice for the initial enrichment of sulfur concentrate. After sorting, most of the gangue tailing can not only eliminate the influence of the slime on the flotation, but also can rush and rub the surface of the tailings by the vibration of the shaker, which is beneficial to the flotation recovery of the sulfur concentrate and subsequent Lead-zinc mine. Under the conditions determined by the ore concentration and the ore concentration, the particle size of the tailings, the stroke of the shaker and the inclination of the bed are all key factors for re-election of the concentrate. For the +0.074mm grain-level tailings, the small stroke, fast flushing and flushing water are used for the small flushing water and the large cross slope for the shaker test; and the -0.074mm grain-level tailings is selected for the large stroke and slow stroke. And the flushing water is subjected to a shaker test for small flushing water and small cross slope. The tailings of No. 1 tailings pond of Fankou Lead-Zinc Mine were graded by 0.074 mm fine screening and re-elected. The test results are shown in Table 3.
It can be seen from Table 3 that, after sorting by a shaker, the sulfur content of the sulfur concentrate is 28.6% in the +0.074 mm granule heavy ore. In the -0.074mm grain size, although the sulfur content in the tailings is relatively low, since the dissociation of pyrite is relatively sufficient, it is easier to separate from the gangue mineral by the re-election method, and the sulfur content in the heavy ore is also reached. 23.5%. The secondary re-election and enrichment of the medium mine, the light mine tailing, can reduce the gangue minerals by about 55% in total, greatly reducing the grinding amount in the next step, saving the grinding cost and enriching the lead. , zinc, silver , antimony , gallium and other valuable metal elements.
(2) Flotation test
The sulfur concentrate obtained after the tailings of the No. 1 tailings pond of Fankou Lead-Zinc Mine is re-elected. On the one hand, the grade of sulfur does not reach the sales standard of 35%, and must be further enriched; on the other hand, the obtained sulfur The total content of lead metals such as lead and zinc in the concentrate has reached about 5%, and it has a good condition for recovering galena and sphalerite. In order to better recover various valuable metals, the flotation test was carried out on the re-elected sulfur concentrate.
1. Effect of grinding time on flotation recovery rate
The tailings of No. 1 tailings pond of Fankou Lead-Zinc Mine has been accumulated for many years. Due to historical reasons, the tailings particles themselves are coarse and the useful minerals are not fully dissociated. Since the particle size is directly related to the recovery rate, it is necessary to carry out the grinding test in order to fully recover valuable elements such as sulfur, lead and zinc. Take 500g of heavy ore sample after re-election of +0.074mm, add 800mL of water, grind in a ball mill with a volume of 5L, and study the effect of grinding time on sulfur recovery rate. The test results are shown in Figure 1.
It can be seen from Fig. 1 that the recovery rate of sulfur in the wet grinding time reaches 80% or more within 8 to 10 minutes. Therefore, the optimum time for wet grinding of tailings is 8 to 10 minutes.
2. Effect of sodium sulfide on flotation recovery
It is known from the mechanism of action of sodium sulfide in flotation that it can temporarily inhibit the flotation of sulfide ore, the inhibition of the ore and sphalerite is strong, and the inhibition of pyrite is the weakest. In some cases, Pyrite can be activated. Comparative experiments show that the tailings that have been wet-milled after re-election are directly flotation at a natural pH of 6.5 (normal value of tailings), increasing the amount of xanthate and 2# oil, prolonging stirring and floatation. The selection time can only make 15% of the galena and sphalerite float. Due to the oxidation of the pyrite surface, some sulfur is produced, which increases the hydrophobicity of pyrite and is beneficial to the flotation of pyrite. The same experiment was carried out after adding a small amount of sodium sulfide before flotation. The galena and sphalerite could hardly float out, and the flotation recovery rate of pyrite reached over 80%, indicating that sodium sulfide did lead and flash. The zinc ore has been temporarily inhibited, and the yellow pyrite has been activated. Due to the long storage time of the tailings, the galena and sphalerite on the surface are partially oxidized. After adding sodium sulfide, the following reaction will occur within a certain period of time:
After a sufficient reaction for a period of time after the addition of Na 2 S, the oxidized PbSO 4 and ZnSO 4 in the tailings form a poorly soluble PbS and ZnS coating with a certain thickness, and the xanthate collector is adsorbed in the galena. It is not easy to fall off like the surface of sphalerite, which improves the floatability of galena and sphalerite, so that some of the oxidized galena and sphalerite in tailings are activated [7] . Lead ore and sphalerite, and improving the recovery rate of lead and zinc play a key role. Therefore, sodium sulfide should not be added too early in the flotation recovery of pyrite, and it should not be added during wet grinding. It must be added with sodium sulfide solution before flotation to achieve the best effect.
The amount of sodium sulfide directly affects the flotation recovery rate of the sulfur concentrate. If the dosage is too small, the galena and sphalerite cannot be effectively inhibited, and the surface of the partially oxidized lead sulfate and zinc sulfate is not sufficiently vulcanized. The recovery rate of lead and zinc flotation is not high; on the contrary, it can inhibit the pyrite, increase the hydrolysis of sodium sulfide, increase the pH of the solution, and is not conducive to the flotation of pyrite, but also increases Pharmacy cost. Take 500g of heavy ore that has been wet-milled for 10min for flotation (sulfur content is 28.6%), and change sodium sulfide under other conditions (butyl xanthate 150g/t, pine oil 40g/t) The amount of sodium sulfide (10% solution was prepared on site and extracted with a syringe). After one rough selection, one selection and two sweeps (the same below), the test results are shown in Table 4.
It can be seen from Table 4 that when the amount of sodium sulfide reaches 800r/t, the recovery rate of sulfur concentrate is the highest, and the grade of sulfur also reaches the requirement of more than 35%. When the amount of sodium sulfide exceeds 800g/t, the recovery rate decreases. The increase in the amount of sodium sulfide does not affect the grade of the sulfur concentrate. The amount of sodium sulfide available for production is 800 g/t.
3. Effect of pH on flotation recovery rate
Take the above-mentioned re-elected and wet-milled heavy ore 500g (sulphur content is 28.6%), and the other conditions (butyl xanthate 150g / t, sodium sulfide 800g / t, pine oil 40g / t) unchanged In the case of H 2 SO 4 and lime, respectively, adjusted to different pH values, and the flotation test was carried out. The test results are shown in Table 5.
It can be seen from Table 5 that when the pH exceeds 7.5, the recovery and yield of the sulfur concentrate rapidly decrease, and the pyrite begins to be inhibited. The grade of sulphur is also gradually decreasing, mainly due to the increase in the content of galena and sphalerite in the concentrate. Obviously, pyrite is more likely to float in acidic medium, but considering the corrosion of equipment and the actual pH of tailings in Fankou Lead-Zinc Mine No. 1 tailings pond is 6.5, the flotation sulfur concentrate The natural state of the pH setting of 6.5 is better.
4. Effect of flotation time on flotation recovery rate
Take the above-mentioned re-elected and wet-milled heavy ore 500g (sulphur content is 28.6%), the pulp pH value is 6.5, butyl xanthate 150g/t, sodium sulfide 800g/t, pine oil 40g/ t. Study the effect of flotation time on recovery rate. The test results are shown in Table 6.
It can be seen from Table 6 that after the flotation time reaches 8 min, although the recovery rate of the sulfur concentrate continues to rise, the grade of sulfur begins to decrease, mainly because the sodium sulfide is lead and flash with the extension of the flotation time. The inhibition of zinc ore is weakened, and some of the galena and sphalerite in the tailings are recovered into the sulfur concentrate, which will lose the most valuable lead-zinc ore in the tailings. The best flotation time in production is 7-8 min.
5. Effect of butyl yellow dosage on flotation recovery
Take the above-mentioned re-elected and wet-milled heavy ore 500g (sulphur content is 28.6%), the pulp pH value is 6.5, sodium sulfide 800g/t, pine oil 40g/t, flotation time is 8min, study The effect of the amount of butyl yellow on the recovery rate is shown in Table 7.
It can be seen from Table 7 that the recovery rate and yield of the sulfur concentrate increase with the increase of the amount of butyl yellow, but when the dosage reaches 150g/t, the recovery rate is not obvious, and the sulfur grade is The increase in the amount of butyl yellow is continuously reduced, mainly due to the recovery of some galena, sphalerite and gangue in the tailings into the sulfur concentrate. The amount of collector used in industrial production is 120-150 g/t.
(3) Small closed circuit test
The whole process small-scale closed-circuit test was carried out on the basis of the above various condition tests. The process flow is shown in Figure 2. A good result was obtained in the flow of Fig. 2, the sulfur grade of the sulfur concentrate was 35.7%, and the recovery rate was 79.5%.
Third, the conclusion
(1) In view of the tailings characteristics of the No. 1 tailings pond of Fankou Lead-Zinc Mine, a new combined process of fine screening, re-election and flotation was used to recover the sulfur concentrate, and satisfactory results were obtained. The small test was obtained. Sulfur concentrate product with a sulfur recovery of 35.7% and a total recovery of 63.5%.
(2) Using 0.074mm fine sieve classification, +0.074mm tailings can be initially enriched in sulfur concentrate, and then re-election and enrichment of tailings respectively, which can make about 55% of gangue mineral tailing, greatly reducing The subsequent grinding and beneficiation costs, while enriching the valuable elements such as sulfur, lead, zinc, silver, gallium and antimony, also improved the subsequent flotation conditions, and can better recover the No. 1 tailings of Fankou Lead-Zinc Mine. Sulfur concentrate in the library.
(3) The conditions for the best flotation recovery of the tailings after re-election are: pulp pH 6.5, butyl xanthate 150g/t, pine oil 40g/t, flotation time 8min, sodium sulfide The best dosage is 800g/t. The location and amount of sodium sulfide added to the activated pyrite, effective inhibition of galena and sphalerite, and played a key role in the recovery of lead, zinc, silver, gallium, antimony and other metal elements.
(4) The new process of recovering sulfur concentrate from lead-zinc tailings, realizing the sustainable use of secondary resources, providing a way to reduce the acidification of lead and zinc tailings ponds, improve the economic and social benefits of enterprises, and protect the environment. A new way to have a good reference value for the recovery of sulfur concentrate in the same type of lead-zinc mine old tailings pond.
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