Sichuan, a lead zinc mine is a medium-sized mining enterprises, processing plant processing capacity of 1000t / d, output lead sulfide concentrate and zinc sulfide concentrates. The main minerals of zinc in ore are sphalerite, smithsonite, heteropolar ore and willemite. The zinc oxidation rate of the ore is 12% to 15%. The zinc grade in the tailings discharged from the ore dressing plant is generally around 2%, of which 90% is zinc oxide. Concentrator tailings discharged every day is about 800 t, tailings line of people every year in approximately about 240 000 t, zinc oxide metal loss is about 4300t. The zinc metal currently dumped in the tailings pond is estimated to be 100,000 tons. Undoubtedly, this is a considerable resource available, and the recovery of zinc oxide from it has important practical significance for the comprehensive utilization of its resources.
For the zinc oxide in the tailings, due to factors such as low grade, high mud content, difficulty in mineral processing, and high production cost, the mineral processing technology and economic problems have not been effectively solved for a long time, and it cannot be recycled. Although the ore dressing workers have conducted a lot of research, they have not made breakthrough progress. In response to this problem, after detailed research on the beneficiation process, the combined process of spiral chute de-sludge, shaker enrichment and flotation was successful, and the zinc oxide concentrate grade was 33% and the flotation recovery rate was 86%. Better indicator.
First, tailings properties
(1) Spectral analysis, main chemical composition analysis and zinc phase analysis
The results of tailings spectral analysis are shown in Table 1. The main chemical composition analysis results are shown in Table 2. The zinc phase analysis results are shown in Table 3.
Table 1 Results of tailings spectral analysis
Table 2 Analysis results of main chemical components of tailings
Table 3 Analysis results of tailings zinc phase
(II) Mineral composition and characteristics of tailings
Tailings primary metal minerals calamine, willemite, hemimorphite, white lead, galena, sphalerite, brown iron ore, magnetite, siderite, pyrite, rutile and the like; gangue minerals are quartz, dolomite, calcite, sericite, chlorite, serpentine like. Tailings contain 0.36% lead and 2.13% zinc. Zinc oxidation rate is 90.7%
The zinc oxide mineral mosaic is complicated, and the fine particles and the particles are unevenly embedded, and both of them are in the shape of grains or are closely embedded in the gangue.
The ore in the ore is replaced along the edge of the sphalerite and the fissures. There are many fine sphalerites in the common smithsonite. Occasionally, the illusion of leucite is galena and the zinc-zinc or smithsonite is embedded in the dolomite. The smithsonite is granulated and vein-like embedded in the gangue, and has a particle size of 0.15 to 0.005 mm. The wurtzite and the heteropolar ore are often embedded in the dolomite together with the white lead ore and have a particle size of 0.02 to 0.006 mm. The white lead ore has a particle size of 5 to 8 μm.
(III) Analysis of tailings particle size
The tailings particle size distribution curve is shown in Fig. 1. From the grain size distribution of the tailings, the yield of the -5μm fraction is 29.11%, and the zinc metal distribution is 23.7%. The yield of -20 μm was 55.41%, and the distribution of zinc metal was 48.06%. It can be seen that the tailings have a higher mud content and a higher occupancy rate of zinc metal, which has a greater impact on the recovery rate of zinc oxide.
Figure 1 tailings size distribution curve
1-cumulative yield; 2-zinc cumulative distribution rate
The chemical composition analysis and mineral composition of the tailings indicate that the tailings is an ore with low zinc grade, high zinc oxidation rate, various metal and gangue minerals, complex embedding, close continuous and uneven particle size distribution. The results of grain size distribution show that the tailings not only have higher mud content, but also the distribution rate of zinc metal in the slime is higher.
Second, mineral processing technology research
For the recovery of zinc oxide, the slime must be controlled. Numerous studies at home and abroad have shown that slime can inhibit the floatability of zinc minerals, leading to a sharp increase in the amount of flotation reagents. Therefore, the recovery of zinc oxide from tailings must first solve the problem of desilting, and secondly solve the problem that the ore dressing cost is higher than the output of the concentrate due to the low zinc grade and there is no economic benefit. According to the characteristics of the tailings, a re-election-flotation combined process was carried out to carry out experimental research on the recovery of zinc oxide from tailings.
(1) Re-election process test
From the particle size characteristics of the tailings, the tailings have a finer particle size, the yield of the -20 μm fraction is 55.4%, and the amount of zinc metal is 48%. In the flotation process of zinc oxide, the effect of the slime is more serious. Exploratory test results show that the flotation of the tailings will seriously affect and interfere with the flotation of zinc oxide when the -20μm fraction of the ore is occupied by 15%. Therefore, this part of the slime should be removed first to create a good condition for zinc oxide flotation.
1, mud removal test
The spiral chute and the de-slipping bucket are better de-slipping equipments, which have the advantages of simple structure, reliable operation, simple maintenance, small floor space, high unit processing capacity, no power consumption, etc. The disadvantages are low classification efficiency and enrichment ratio. small. In this study, a spiral chute and a de-flushing bucket were compared (the results are shown in Table 4). The test results show that the desilting effect of the spiral chute is better than that of the de-flushing bucket. The spiral chute not only removes a large amount of slime, but also slightly enriches the zinc.
Table 4 Results of desilting test of spiral chute and mud removal bucket
From the perspective of the coarse concentrate obtained from the spiral chute, the use of a single spiral chute can not meet the needs of flotation, mainly because the zinc-containing grade is low (only 2.3%). If the direct flotation cost is high, the spiral will be spiraled. The coarse concentrate is further subjected to shaker enrichment to obtain a higher grade zinc oxide coarse concentrate. The main disadvantage of the shaker is that it has a large footprint and low processing capacity, but this unfavorable condition has been reduced to a low level after a large number of tails have been thrown through the spiral chute. It is more practical to pre-treat the tailings by integrating the advantages of the two equipments of spiral chute and shaker.
For the selection of the shaker, one hopes that the zinc recovery rate of the shaker concentrate is as high as possible, and the second is that the concentrate grade is as high as possible, so that the technical and economic indicators of the subsequent flotation system are better, but this is in production practice. It is difficult to achieve. Therefore, the selection of the shaker has a problem of determining the yield of the better concentrate. In order to determine the economic yield of the shaker concentrate, the different shaker concentrates produced were subjected to flotation tests under the same flotation conditions to study the yield, grade and recovery of the zinc oxide concentrate produced by flotation. Correspondence with the shaker concentrate yield in order to more accurately determine the economic yield of the shaker concentrate. The results of the shaker test and the flotation test are shown in Tables 5 and 6, respectively.
Table 5 Shake test results
Table 6 Exploratory test results of shaker concentrate flotation
From the results of the shaker test in Table 5, it can be seen that when the shaker concentrate yield is 49.36% and 36.34%, the zinc grade is 3.49% and 4.66%. At this time, the recovery of the well is not much different, about 74%; When the bed concentrate yield was reduced to 26.47%, the zinc concentrate grade increased to 5.7% and the recovery rate decreased by 8% to 9%. From the flotation test results of three different grades of shaker concentrates in Table 6, it can be seen that the shaker concentrate flotation of different zinc grades has little effect on the grade of flotation concentrate, but there are some yields and recovery rates. Larger impact, when the grade of the shaker concentrate (flotation to the mine) is gradually increased, the yield and recovery rate of the flotation coarse concentrate is rising for the flotation operation, but decreases for the original ore. From the data of Group 3, it is seen that when the ore grade is higher, the yield and recovery rate of the flotation coarse ore to the ore are lower. That is to say, the grade of the shaker concentrate is not as high as possible, and there should be a reasonable grade and corresponding economic yield. It is necessary to consider increasing the grade of the shaker concentrate as much as possible, reducing the flotation treatment capacity and reducing the flotation cost. It is also necessary to consider increasing the recovery rate of the flotation to the original ore and maximizing the recovery of zinc oxide from the tailings. .
After repeated trials and comparison of technical and economic indicators, it is more appropriate to select the zinc grade of the shaker concentrate at about 4.6% and the concentrate yield to be about 16%. At this time, the comprehensive index of zinc oxide recovery is higher.
2, spiral chute - shaker combination process test
The selection result of the tailings through the spiral chute-shaker combination re-election process is listed in Table 7, and the flow is shown in Figure 2. From the results in Table 7, it can be seen that the ore content is intercepted according to the economical efficiency of the shaker determined by the experiment, and the selection index of the zinc grade of the shaker concentrate is 4.63% and the recovery rate is 73.41%, which is the subsequent float of zinc oxide recovered from the tailings. The selection process has created better conditions.
Table 7 Test results of spiral chute-shaker combination process
Figure 2 spiral chute-shaker beneficiation process
(2) Flotation process test
The test of the zinc oxide flotation part was carried out by using the shaker concentrate as the ore.
1. Sodium sulfide + sodium carbonate dosage test
The experiment conducted an exploratory test on the ratio of sodium sulfide to sodium carbonate. The results showed that the ratio of sodium sulfide to sodium carbonate was 4:1. The dosage test was carried out according to this ratio, and the flow is shown in Fig. 3. The test results are shown in Fig. 4. The results showed that the zinc recovery rate increased rapidly with the increase of sodium sulfide and sodium carbonate. When the total amount of sodium sulfide and sodium carbonate reached 5.0 kg/t, the recovery rate was higher, and the zinc content and recovery rate decreased. . The total amount of sodium sulfide + sodium carbonate is 3200+800 g/t, and it is better to sweep 800+200 g/t.
Figure 3 Zinc oxide flotation conditions test procedure
Figure 4 Na 2 S + Na 2 CO 3 ( 4:1) dosage test results
1-zinc grade; 2-zinc recovery
2, water glass dosage test
The results of the material composition of tailings indicate that the gangue minerals in tailings are mainly quartz, calcite, dolomite, sericite, chlorite and serpentine. Although the tailings have been sorted by spiral chute + shaker combination process, the content of impurities in the coarse concentrate is still high, including SiO 2 38.76%, CaO 11.91%, MgO 12.33%, Al 2 O 3 8.15%, Fe 2 O 3 4.15%. Therefore, the use of water glass to inhibit gangue minerals is beneficial to improve the grade of zinc oxide concentrate. The principle flow of the water glass dosage test is shown in Figure 3, and the test results are shown in Figure 5. It can be seen from the results that when the amount of water glass is 300 g/t, the selection index is better.
Figure 5 Water glass dosage test results
1-zinc grade; 2-zinc recovery
3, collector E-3 dosage test
The principle flow of the E-3 dosage test is shown in Figure 3, and the test results are shown in Figure 6. The results show that the zinc recovery rate increases with the increase of the amount of E-3, and the index is better when the total amount of coarse sweep is 240g/t.
Figure 6 E-3 test results
1-zinc grade; 2-zinc recovery
4, flotation process open circuit test
On the basis of the rough sweeping adjuster and the collector dosage test, a selective test was carried out. The test results show that it can be selected twice, and it is better to add a little collector in the selection II. The open circuit test procedure for flotation is shown in Figure 7, and the results are shown in Table 8. According to the test results, using the test conditions, the open-circuit test obtained zinc oxide concentrate index of 34.64% zinc grade and 82.44% flotation recovery rate.
Figure 7: Recovery process of zinc oxide open-circuit flotation from tailings
Table 8 Flotation open circuit test results
(III) Closed-circuit test of re-election-flotation process
In order to further verify the above research results of the beneficiation process, the re-election and flotation process were combined to conduct a full-process closed-circuit test. The test procedure is shown in Figure 8, and the test results are listed in Table 9. The results show that the re-election-flotation combined process is smooth and applicable. The concentrate grade obtained by the shaker is 4.59%. The zinc grade is 33.35% by flotation, the flotation recovery rate is 85.99%, and the ore supply (tailing) Recovery rate of 30.82% of zinc oxide concentrate.
Figure 8 Closed-flow process of re-election-flotation combined beneficiation process
Table 9 Re-election - Selecting the combined process flow closed-circuit test results
Third, the conclusion
(1) Spectral analysis, chemical multi-element analysis, zinc phase analysis, tailings mineral composition and related characteristics analysis of a lead-zinc mine tailings in Sichuan showed that the zinc grade in the tailings was 2.13%, 90% of which was oxidized. Zinc, the main oxidized mineral is zinc carbonate, which accounts for about 85%, and zinc silicate and others are 5.5%. The main characteristics of the tailings are high mud content, large gangue volume and low zinc grade. The results of particle size analysis showed that the yield of -20 μm was about 55%, and the distribution of zinc metal was about 48%.
(II) In view of the characteristics of the tailings, this study solved the recovery of zinc oxide ore from lead-zinc tailings by using the spiral chute de-sludge, shaker enrichment and flotation re-election-flotation combined process. Puzzle. The closed-circuit test obtained a good zinc oxide concentrate index of 33.35% zinc grade and 58.99% flotation recovery rate. This study has important practical significance for the comprehensive utilization of lead and zinc tailings resources.
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