China's lead-zinc ore mostly associated with silver, but silver ore mineral composition and more complicated and the relationship between particle size distribution uneven thickness, is inconsistent with the floating characteristics of the main reasons lead minerals with other minerals embedded, comprehensive recovery of silver has not High, resulting in waste of resources.
The lead, zinc and silver grades of ore processed in a lead-zinc mine in Jiangsu are about 4%, 7% and 170g/t respectively. The current recovery rate of silver in lead concentrate is only about 55%. In order to improve the comprehensive utilization rate of resources and the economic benefits of enterprises, the ore was tested to improve the recovery rate of associated silver.
First, the nature of the ore
Metal ore minerals are mainly pyrite, galena, sphalerite, copper ore, diamond ore manganese, zinc, antimony tetrahedrite, tetrahedrite like silver, wherein the silver zinc, antimony minerals tetrahedrite, Silver bismuth copper ore, fluorite ore, etc.; gangue minerals include dolomite, calcite , feldspar , quartz , carbonaceous materials, and the like.
The silver mineral in the ore has a complex embedded relationship and a fine grain size. Among them, the silver-bearing ore is encapsulated in galena; some of the zinc-copper and copper-silver-copper ore are fine-grained inclusions (0.002~0.011mm) embedded in pyrite, this part of fine-grained zinc It is difficult to separate the beryllium copper and the silver beryllium copper ore, which will be lost in the sulfur concentrate, thus directly affecting the flotation recovery rate of silver. The results of multi-element analysis of raw ore are shown in Table 1, and the results of silver phase analysis are shown in Table 2.
Second, on-site process analysis
Lead-silver mineral processing plant is currently the flotation process are: the grinding fineness is -74μm 70%, twice as a roughing process, selection of four times, four times sweep the election, the reagent system for the high alkalinity (PHl2.5 Under the conditions, zinc sulfate and sodium sulfite are used as adjusting agents, ethyl sulfide nitrogen is used as collector, and pine oil is used as foaming agent for flotation of lead-silver concentrate. Production indicators are shown in Table 3.
It can be known from the ore properties that the silver mineral inlays are fine in size and need to be finely ground to fully dissociate; the silver minerals are mainly zinc beryllium copper ore and silver beryllium copper, etc. These two minerals can float under moderately weak alkaline conditions. The sex is the best; the other ore contains high carbon and needs to be targeted.
According to the nature of the ore, this study intends to improve the recovery rate of silver by improving the fineness of grinding and reducing the alkalinity of flotation. Reducing the alkalinity of flotation pulp will inevitably reduce the inhibition of pyrite and affect the lead grade of lead-silver concentrate. Therefore, it is proposed to add sodium sulfide as a regulator during the grinding process to strengthen the inhibition of pyrite and ensure the fineness. Mineral grade; at the same time, it is proposed to add selective collector BK901C to copper and silver minerals to enhance the flotation of silver; to add a certain amount of diesel to carbonaceous materials, to eliminate the influence of carbonaceous materials on the flotation process and ensure the recovery rate of silver . Due to changes in the flotation atmosphere, it is proposed to adjust the lead collector to ensure that the lead recovery rate is not affected.
Third, the condition test
A series of comparative tests were conducted based on the proposed process measures to improve the silver recovery rate.
(1) Grinding fineness test
The test procedure is a rough selection. The test conditions are to add lime to the grinding process to adjust the pH to 12.5, add zinc sulfate 1000g/t, sodium sulfite 1000g/t, add ethyl sulphide 50g/t and pine oil 30g// during the flotation process. t, flotation time 6min. The test results are shown in Figure 1.
It can be seen from Fig. 1 that proper improvement of grinding fineness can significantly improve the silver recovery rate without any negative impact on the lead grade and recovery rate. Therefore, the fineness of grinding should be -74μm, which accounts for 80%.
(2) pH condition test
The test procedure is a rough selection. The test conditions are grinding fineness -74μm, accounting for 80%. Calcium is added during the grinding process to adjust the pH. Add zinc sulfate 1000g/t, sodium sulfite 1000g/t, and add ethyl sulphide 50g during flotation. /t, pine oil 30 g / t, flotation time 6min. The test results are shown in Figure 2.
It can be seen from Fig. 2 that under moderately weak alkaline conditions, the inhibitory effect on pyrite is weak, some pyrites are floating, and the lead grade in the coarse concentrate is reduced; the lead collector ethylene sulfide in the medium weak base The capture performance under the conditions is also weakened, resulting in a decrease in lead recovery rate in the coarse concentrate. However, when pH is 0.50.5, the silver recovery rate reaches a maximum. Considering the trade-off, the lead grade and recovery rate in coarse concentrate can be compensated by other technological measures, so the pH value of flotation should be 10.5.
(3) Sodium sulfide dosage test
The test procedure is a rough selection. The test conditions are grinding fineness -74μm, accounting for 80%. Calcium is added during the grinding process to adjust the pH to 10.5, adding sodium sulfide, zinc sulfate 1000 g/t, sodium sulfite 1000 g/t, flotation process. Adding ethyl sulphide nitrogen 50 g/t, pine alcohol oil 30 g/t, flotation time 6 min. The test results are shown in Figure 3.
It can be seen from Fig. 3 that the addition of an appropriate amount of sodium sulfide can enhance the inhibition of pyrite to eliminate the effect of lowering the pH value on the lead grade in the coarse concentrate. However, excessive sodium sulfide also inhibits lead minerals and copper-silver minerals, affecting the recovery of lead and silver. Therefore, the amount of sodium sulfide should be 200g / t.
(4) BK90lC dosage test
The test procedure is a rough selection, the test conditions are grinding fineness -74μm accounted for 80%, lime is added during the grinding process to adjust the pH to 10.5, sodium sulfide 200 g / t, zinc sulfate l000g / t, sodium sulfite 1000g / t, During the flotation process, BK901C, ethyl sulphide nitrogen 50g/t, pine oil 30g/t were added, and the flotation time was 6min. The test results are shown in Figure 4.
As can be seen from Fig. 4, the addition of an appropriate amount of copper-silver selective collector BK901C can significantly improve the silver recovery rate. Excessive BK901C will make the flotation foam too thick and the amount of foam is too rich, which will deteriorate the flotation process and affect the lead grade in the coarse concentrate. Therefore, the amount of BK901C should be 10g / t.
(5) Diesel consumption test
The test procedure is a rough selection. The test conditions are grinding fineness -74μm accounting for 80%. Calcium is added during the grinding process to adjust the pH to 10.5, sodium sulfide 200g/t, zinc sulfate 1000g/t and sodium sulfite 1000g/t. During the selection process, diesel oil, BK901C 10g/t, ethyl sulfur nitrogen 50g/t, pine alcohol oil 30g/t were added, and the flotation time was 6min. The test results are shown in Figure 5.
It can be seen from Fig. 5 that adding an appropriate amount of diesel oil can effectively eliminate the influence of carbonaceous materials in the ore on the flotation process and increase the silver recovery rate. However, excessive diesel will reduce the flotation foam and reduce the recovery rate of silver and lead. Therefore, the amount of diesel oil should be 30 g / t.
(6) Comparative test of lead collector
The test procedure is a rough selection. The test conditions are grinding fineness -74μm accounting for 80%. Calcium is added during the grinding process to adjust the pH to 10.5, sodium sulfide 200g/t, zinc sulfate 1000g/t and sodium sulfite 1000g/t. During the selection process, diesel oil 30g/t, BK901C 10g/t plus, lead collector, and pine oil 30g/t were added, and the flotation time was 6min. The test results are shown in Table 4.
It can be seen from Table 4 that by adjusting the lead collector, the effect of reducing the pH value of the flotation on the lead recovery rate can be compensated. When the lead collector is selected from ethyl sulphide 15g/t+ aniline black medicine 35g/t, the lead recovery rate is basically the same as the current process.
In summary, the current process of the concentrator is improved to grind fineness -74μm accounted for 80%, flotation pH 10.5, new 200g/t sodium sulfide during grinding, and 10g/t BK901C added during flotation 30g / t diesel, lead collector using ethyl sulphide 15g / t + aniline black medicine 35g / t, can maintain the lead grade and recovery rate is basically unchanged, greatly improve the recovery rate of silver.
Fourth, closed circuit comparison test
The on-site process flow was kept unchanged, and the closed-circuit comparison test was carried out on the basis of the open circuit test using the on-site flotation process and the improved flotation process. The closed-circuit test process is shown in Figure 6, and the test results are shown in Table 5.
It can be seen from Table 5 that the application of the improved process increases the recovery rate of silver from 51.86% to 85.43%, which is increased by 33.57%, while maintaining the grade and recovery rate of lead substantially unchanged.
V. Conclusion
(1) The silver minerals associated with the lead-zinc ore are mainly zinc beryllium copper ore, silver beryllium copper or silver-silver ore, which have complex occurrence characteristics and fine inlaid grain size.
(2) The current process of applying the current process in the ore dressing plant, the recovery rate of silver in lead concentrate is only about 50%.
(3) Closed-circuit comparison test results show that the application of the improved new process can greatly increase the recovery rate of silver by 33.57%.
references
[1] Xie Xuefei, Luo Sheng. Research and practice of comprehensive recovery of associated silver under high alkali conditions [J]. Mining and Metallurgical Engineering, 2002, 22 (1): 58-60.
[2] Liang Dongyun. Study on the occurrence state of associated silver in a hydrothermal sedimentary ore[J]Acta Mineralogica Sinica, 2001, 21(3): 534-536.
[3] Wang Gengchen, Wei Dezhou. Flotation separation of silver-lead-zinc sulfide ore in Xitie Mountain [J]. Metal Mine, 2005, (11): 27-33.
[4] Huang Feng combat translation. Flotation of silver-bearing minerals in complex sulfide ore [J]. Nonferrous Mines, 1997, (5): 18-22.
[5] Liu Wang. Improve the recovery rate of associated silver in lead concentrate [J]. Mineral Protection and Utilization, 2001, (3): 33-35.
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