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Study on Beneficiation Process of Low Grade Silver Manganese Ore in a Certain Area of ​​Hebei Province
Silver manganese ore is an important source of metal ore smelting silver, with the growing depletion of metallic silver and growing demand for high-grade silver ore resources in recent years the development and utilization of low-grade silver ore resources of the enterprise began to receive attention. The study found that the low-grade silver-manganese ore contained manganese minerals with fine grain size, while silver and manganese minerals were tightly bound, and it was difficult to separate them effectively by the beneficiation method. However, the direct immersion silver process could not achieve high recovery, so for low-grade silver Manganese ore uses a beneficiation-leaching process. In this paper, the low-grade silver-manganese ore in a certain area of ​​Hebei Province was studied in the process of beneficiation and purification, and achieved good results.
First, the nature of the ore
(1) Multi-element and phase analysis of ore chemistry
Representative ore samples were taken for multi-element and phase analysis. The results are shown in Tables 1 and 2.
Table 1 Multi-element analysis results of raw ore (mass score) /%
Ag 1)
Au 1)
Cu
Pb
Zn
S
Mn
TFe
210.8
0.58
0.01
0.01
0.02
0.038
4.14
1.14
1) The unit is g/t.
Table 2 Analysis results of raw ore silver phase and manganese phase
Silver phase
content
/(g·t -1 )
Occupancy rate /%
Manganese phase
Manganese content /%
Occupancy rate /%
Natural silver
67.3
31.9
Rhodochrosite
0.52
12.53
Silver oxide
7.8
3.7
Manganese ore,
Manganese ore
0.94
22.65
Silver sulfide
4.9
2.3
Pyrolusite
2.69
64.82
Silver chloride
1.1
0.5
total
4.15
100.00
Other silver
130.0
61.6
total
211.1
100.0
(2) Mineral composition of raw ore
The ore is in a granular structure. The mineral composition is simpler but not evenly distributed. Metallic minerals content of about 5%, was predominantly manganese (manganese ore, manganese brown, water and rhodochrosite manganese), native silver, a small amount of hematite and magnetic iron ore; non-metallic mineral content of about 95%, mainly Quartz and carbonate minerals ( calcite, etc.), quartz content of 60% to 65%, carbonate mineral content of 30% to 35%; followed by a small amount of amphibole and zoisite. It has a phenomenon of petrochemical alteration of sodium curtain.
(3) Main mineral inlay characteristics
The ore and ore in the ore is the main manganese-bearing mineral in the ore and the main carrier mineral of silver. The silver mineral is often encapsulated in the fine particle state. The pyrolusite and the hard manganese ore are closely embedded, and the pyrolusite is often formed into the hard manganese ore. The band-shaped or concentric layered structure, the contact boundary between the two is not obvious, and the transition type has uneven grain size.
The main metal mineral is pyrolusite, which is mostly in the form of granules, and some of them are needle-like aggregates. The size of the inlaid cloth is mainly fine particles, generally 0.01 to 0.197 mm. The type of inlay is mainly connected and partially wrapped. The former is mainly characterized by the installation of pyrolusite with quartz and calcite. The latter is mainly characterized by the inclusion of pyrolusite in the form of granular particles in quartz and amphibole gangue minerals.
The brown manganese ore is mostly in the form of granules, and is irregularly adjacent to the gangue minerals. The particles are generally 0.01 to 0.2 mm.
Natural silver is mostly in the form of granular and round dots distributed in quartz and calcite gangue minerals. The size of the inlaid cloth is mainly fine particles, generally 0.002 to 0.016 mm.
Second, the design of the ore dressing test plan
Studies on the properties of the ore have shown that the silver in the ore is mainly composed of silver manganese ore and natural silver. The most effective means of recovering natural silver is flotation, while the recovery of manganese ore is either strong magnetic or flotation. Since manganese minerals have weak magnetic properties, it is feasible to use strong magnetic separation recovery. The manganese is also enriched in silver, but the soft manganese ore grinding is easy to produce fine mud. Because the particles are extremely small, strong magnetic separation is difficult to recycle. Lost in the tailings, this part of manganese ore can only be recovered by flotation or selective flocculation, but the technical difficulty is large.
In general, strong magnetic separation is an effective means to select silver-manganese minerals. For natural silver, it is mostly in the form of granular and polka-like minerals in quartz and calcite gangue minerals. Silver recovery is poor, and flotation is a suitable method for natural silver recovery. However, there are two processes of "flotation-magnetic separation" and "magnetic separation-flotation". The advantage of the "flotation-magnetic separation" process is that the flotation operating conditions are easy to control. In order to meet the particle size requirements of flotation, the ore needs to be ground before flotation, but the manganese ore mud will increase more when the ore is finely ground, and the recovery rate of strong magnetic separation will be reduced, which is the disadvantage of the “flotation-magnetic separation†process. . The "magnetic separation-flotation" process can perform strong magnetic separation under coarse-grained conditions, with less manganese ore and higher recovery of strong magnetic separation, which is the advantage of the "magnetic separation-flotation" process. At the same time, the results of the two process test data also illustrate this point. For example, using the flotation-magnetic separation process, a silver concentrate sorting index with a yield of 19.98%, a grade of 745.6 g/t, and a total recovery of 69.68% can be obtained. The magnetic separation-flotation process can obtain a silver concentrate sorting index with a yield of 31.83%, a grade of 526.4 g/t, and a recovery rate of 74.87%. Therefore, the results of the two process tests were combined to determine the magnetic separation-flotation process.
Third, the beneficiation process and test results
According to the design process of the beneficiation process, it is determined that the low-grade silver-manganese mine in a certain area of ​​Hebei will be recovered by the “magnetic separation-flotation†process. Because manganese mineral grinding will produce more difficult-to-recover manganese ore mud, strong magnetic separation will be used to obtain manganese minerals under coarse-grained conditions, and then fine flotation is used to recover natural silver, and then silver is floated and then manganese ore is floated. The closed-circuit process test was carried out in the order of “rough grinding—strong magnetic separation—fine grinding—flotation silver—flotation manganese sludge. The process flow is shown in Figure 1, and the mass quality process is shown in Figure 2.
Figure 1 Magnetic separation - flotation process
Figure 2 Magnetic separation - flotation test process
It can be seen from Fig. 2 that the technical index of the process is: manganese silver concentrate contains 595.7g/t of silver, and the recovery rate is 57.26%; strong magnetic tailings are reground to -0.074mm, and the grain size is 75%, then flotation of natural silver, One rough selection, two sweeps, and two selections, the obtained silver concentrate contains 7328.0g/t of silver and the recovery rate is 12.35%. The floating silver tailings re-floats the manganese ore, after one rough selection, one sweep, one time. Selected, the concentrate contains 288.7g/t of silver and the recovery rate is 11.83%. The total recovery of the above three kinds of concentrates is 81.44%, the total average grade is 586.8g/t, the average manganese grade is 11.37%, the total manganese recovery is 83.65%, and the silver tail silver grade is 58.4g/t. The manganese grade is 0.97%. The reason why the silver grade in the tailings is high is that some silver minerals are encapsulated in the pyrolusite in the state of fine particles. Because the soft manganese ore is easily muddy during the grinding process, it is difficult to recover by strong magnetic separation and flotation. This part of the fine-grained silver and the pyrolusite are lost together in the tailings, and it is currently difficult to achieve effective recovery of this part of the silver mineral.
Fourth, the conclusion
(1) Using a magnetic float process to treat a low-grade silver-manganese ore, a silver concentrate with a recovery rate of 81.44% and a grade of 586.8 g/t and a manganese concentrate with a recovery rate of 83.65% and a manganese grade of 11.37% can be obtained.
(2) If it is intended to further improve the concentrate grade, strong magnetic separation can be carried out under fine grinding conditions. The grade of strong magnetic concentrate can be higher than 1000g/t, while the yield of concentrate is reduced, the recovery rate is reduced, and the manganese ore mud is increased. The yield and recovery rate of subsequent flotation manganese ore will increase.
(3) Most of the silver in the manganese-silver concentrate is distributed in the manganese minerals in the molecular state. Therefore, the separation of manganese and silver can only be done by chemical methods such as roasting and leaching. Further research is needed in the future.