The technology of mining alluvial placers by dry method in winter

The technology provides for full-fledged dry mining of placers precisely at a time when traditional technologies stop working due to low ambient temperatures.

After the end of the washing season, traditional technologies are being preserved, and the landfill is being prepared for the next season: it is being insulated, drainage channels are being cleaned, etc. The working staff is going home.

The proposed technology allows, with a break of about one month before the onset of cold weather, to resume gold mining and continue it until the first thaw. The additional period of full-fledged operation of the technology is 6-8 months, depending on climatic conditions.

Figure 1 shows the technological scheme of the processing unit circuit with a capacity of 100-150 m3/hour.

As can be seen from the diagram, frozen sands with a grain size of 600 mm (the size is specified with the miners) are fed into the AEROFLOT self-grinding mill (1) with a drum size of DxL=8.9×1.2 m. During disintegration, the finely dispersed fraction (-0.5+0 mm), as well as the released ice floes, are sucked out of the mill by means of a fan (13) (1). The aspirated part of the product first enters the cyclone (8), where it is divided into a thin fraction, which enters the tailings through the filter (12), and a large, presumably gold-containing fraction, which is sent to the planetary ball mill (7) for enrichment. The product passed through the grate of the AEROFLOT mill (1) with a grain size of less than 40 mm (depending on the number of gali, the grid cell size can be 20 mm or 60 mm) enters the screen (2) with a screen cell size of 20×20 mm (depending on the quality of disintegration, material properties, the number of gali and the presence of nuggets, the screen cell size It can be 10×10 or 5×5 mm. The upper product of the screen (2), completely cleaned of gold–bearing sand, is sent to the dump, the lower product is sent to the planetary self-grinding mill (3). The final purification of the pebble material and the disintegration of the sandy gold-containing product takes place in the mill (3). The disintegrated product is fed to a dry-mode jigging machine (5) for enrichment using an elevator (4). Machine tails (5) with a size of -20+10 mm or -20+5 mm (the size class is selected depending on the presence or absence of nuggets) are sent to the dump.
The heavy superlated fraction -20 +10 (-20+5) mm is unloaded separately and immediately enters the ore collecting table (17), where nuggets are selected.
The sublattice fraction of the jigging machine (5) with a grain size of -10 +5 mm is sent to the re-cleaning machine (6), where tails with a grain size of -10 +5 mm, a superlated concentrate of the same size and a sublattice product with a grain size of -5+0 mm are also obtained. Tailings and superlated concentrate are sent to the appropriate processing units: to the dump and to the ore collection table (17), and this is where their cycle ends. The sublattice product of the jigging machine (6) is sent to the planetary ball mill (7) for enrichment. The enrichment in the mill is due to the difference in the properties of gold and quartz-feldspar sand. The malleability of gold and the brittleness of sand make it possible to obtain crushed sands (less than 70 (40) microns) and flattened gold. Such a product, entering a special separator (9), is easily separated into gold and a finely dispersed part. The gold-bearing fraction enters the sieve (15), where it is divided into size classes. As a rule, in fractions larger than 0.5 (0.1) mm, the concentration of gold is 70-90%. A fraction of less than 0.5 mm, if it contains economically significant gold, is also divided into classes -0.5+ 0.1 and -0.1+0.04 mm, where the concentration of gold reaches 30 and 1%, respectively.

The installation is located on collapsible metal structures and is protected from wind and snowstorms by an unheated building. The ore warehouse, as well as the feeding conveyor (not shown in the diagram) are also located indoors. The volume of ore in the warehouse can ensure the operation of the plant for 12-15 hours. Adjacent to the working building of the installation are residential wagons with the help of galleries — houses, a laundry room, a sauna, a dining room, and a relaxation room. The power supply is provided by a 1.5 MW diesel generator, the cooling system of which is connected to the indoor heating system.

The production time of the installation is 8-9 months.

     The proposed technology would enable, with a lapse of approximately one month prior to the onset of the cold season, to resume and extend gold mining operations until the first signs of thaw.

     The extended period of uninterrupted functioning of the technology ranges from 6 to 8 months, contingent upon climatic factors.

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