RU2309804C1 - Method of dry concentration of lean auriferous gravel - Google Patents

Abstract

FIELD: gold-mining industry; methods of dry concentration of auriferous gravel.

SUBSTANCE: proposed method employs the gravitational pneumatic system. Dry auriferous gravel is ground in centrifugal impact mills to size of 1.0^+0.05 mm and is dried to relative moisture content of 10-15%. Then ore is poured into bin having the slot at its end whose width is equal to 1.1 mm; this slot changes to taper chute inside which flat slotted nozzle is placed. This nozzle is used for forming the slotted injector. Compressed air is delivered to nozzle through receiver with the aid of compressor and reducer and ground ore is removed from bin and is sprayed into separator in form of flat jet. Then, flat jet is split into two flows by means of sailing effect and gravity force. Lower flow contains platinum metals and gold and upper flow contains particles whose sailing effect is twice as much as compared with particles of lower flow. Separation is performed with the aid of adjustable projection; then, concentrate of platinum metals is gathered together with gold in separator bin and is transferred with the aid of conveyer for final extraction of gold. Remaining components and compounds go to waste. Provision is made for sieves-screens which exclude clogging of slotted injector; besides that, injector surface is provided with mechanical vibrator working at frequency of 150-250 Hz and amplitude of up to 2 g. Adjustable swivel projection ensures selective separation of ore into two fractions; this projection is provided with control electric drive.

EFFECT: increased extraction of gold from lean auriferous gravel; all-season gold mining operations.

1 dwg

Description

The invention relates to the gold mining industry, in particular to methods for dry processing of placer gold ore. It is these methods that provide the greatest economic effect in gold mining, especially in regions with a harsh climate.

Modern enrichment methods are based on the separation of minerals and elements according to specific gravities in water (wet enrichment), separation according to specific gravity in an ascending air stream (deposition), magnetic permeability (magnetic enrichment), wettability of surfaces (flotation), centrifugal action (centrifugation), by melting point, etc.

The most effective dry enrichment is carried out by centrifugation (German Patent No. 10715997 with priority 11.11.1957).

The known method of dry magnetic enrichment of mineral raw materials (Russian Patent No. 2156661 with priority 27.05.1997).

Known methods of dry separation of grain into fractions according to the speed of soaring (Russian Patent No. 2166385 and 21760).

Closest to this patent application is Patent of Ukraine No. 60254A dated 09/15/2003 on "Method for separating a granular mixture in a fluid and a device for its implementation." This method is based on scanning high-frequency air flows of bulk materials in a fluid medium with their separation into several fractions.

The methods described above are either expensive and difficult to operate, or do not adequately enrich poor alluvial gold ores (up to 6 g / ton).

The technical result of the present invention lies in the fact that it is proposed a more efficient dry method of extracting gold from poor alluvial gold ore, which allows for year-round gold mining in the northern regions of the country.

The method is based on the fact that there are only 4 elements (osmium, iridium, platinum and rhenium) heavier than gold. These metals are mainly platinum and in nature they are almost always found together and most often in a native state. Tungsten has the same specific gravity as gold (19.3 g / cm ³ ). The rarest of these metals in the earth's crust is iridium (10 ^-7 % by weight), and the most common is osmium (5 · 10 ^-6 %), gold occupies an intermediate position.

If this group of metals together with gold can be separated from the rest into a final concentrate, then further fine separation can be easily carried out due to the large difference in the melting temperatures of gold (1064 ° С) and other metals:

osmium 3027 ° C iridium 2447 ° C platinum 1769 ° C rhenium 3180 ° C tungsten 3370 ° C

Therefore, when developing a method of dry enrichment, the task was set to bring this group of metals together with gold into concentrate, and send everything else to the tail.

The proposed method is carried out in the following way (see drawing). They take dry alluvial gold ore, grind it in centrifugal impact mills to a size of 1.0 ^{+ 0.05} mm (this is the most characteristic grinding size for alluvial ore), dry it to a relative humidity of 10-15% and fill it in hopper 1, at the outlet of which there is a slot 2 1.1 mm wide that passes into a conical flat tray 3, inside of which a flat slotted nozzle 4 is placed, which form a slotted injector 5. Compressed air is supplied to the nozzle through a compressor 6 through a receiver 7 and a gearbox 8 and it is carried away with crushed ru from the hopper 1 and spray it with a flat, in the form of a film, jet into the separator 9. As the flow expires, the flat jet is split into two streams using the effect of windage and gravity, one of which the lower stream (concentrate) 10 contains platinum metals and gold, and the upper stream (tail) 11 other elements and compounds with a specific gravity substantially less than the specific gravity of gold. The separation is carried out using an adjustable, swivel protrusion 12, after which the platinum metal concentrate together with gold is collected in the separator hopper 13 and transferred to the final gold extraction operation. The remaining elements and compounds located in the ore from the hopper 14 are sent to the dump, and the soaking dust formed in the separator 9 is removed by the fan 15.

To ensure greater productivity of the method, several separators are used, combined into a single pneumatic system with a slit length of 2 to several meters, while preventing the possibility of clogging the slotted injector 5 by installing a mechanical vibrator 16 on its surface with a frequency of 150-250 Hz and an amplitude of up to 2 g.

Ensuring selective separation of ore into two fractions is carried out by an adjustable rotary ledge 12 with a control electric drive 17.

Consider, as an example, the possibilities of the attached method to ensure effective separation of ore into fractions.

The main characteristics of separation in this case are the windage of the particles and the speed of their movement.

Sailing of particles is determined by the ratio f / m, where f is the surface area of the particle, and m is the mass of the particle.

At f = const, the windage of the particle will be inversely proportional to its mass.

The soaring speed is the minimum gas flow rate at which particles, after separation, continue to soar in the air without dropping.

If by P we denote sailing, then

where d is the particle diameter, cm,

γ is the specific gravity of the particles.

The ratio of the sail of particles for different fractions is equal to:

For particles an order of magnitude smaller than 1.0 mm, the speed of movement does not exceed 1.8 m / s (determined by the formula of V.D. Arkhangelsky) and refers only to dust generated by the friction of sand and clay particles. This dust is removed from the separator 9 using a fan 15.

The situation is somewhat more complicated with the separation of gold and platinum metals from the main widely distributed components of ore: sand, clay, crushed stone, pebbles and iron.

The average windage of particles of the gold fraction with platinum metals will be 2.6 cm ² / g, and the windage of particles of the second fraction will be 26 cm ² / g.

Thus, the windage of particles of the first fraction will be an order of magnitude lower than the windfall of particles of the second fraction, which contributes to a higher separation coefficient.

If the mill does not provide the desired grinding size, then in order to prevent particles larger than 1.1 mm from entering the slotted injector, the crushed ore is first passed through the corresponding vibrating sieves (screens).

Claims (1)

A method of dry beneficiation of placer gold ore using a gravity-pneumatic system, characterized in that they take dry alluvial gold ore, grind it in centrifugal impact mills to a size of 1.0 ^{+ 0.05} mm, dry to a relative humidity of 10-15% and pour it into the hopper, at the exit of which a slot with a width of 1.1 mm is placed, which passes into a conical flat tray, inside which a flat slot nozzle is placed, with the help of which a slot injector is formed, into this nozzle using a compressor through the receiver and the eductor supplies compressed air and entrains the crushed ore from the hopper and spray it with a flat, film-shaped jet into the separator; as the flow expires, the flat stream is split into two streams by the effect of windage and gravity, of which the lower stream contains platinum metals and gold, and the upper stream contains particles with a windage an order of magnitude greater than the windage of the particles of the lower stream, the separation is carried out using an adjustable protrusion, after which the platinum metal concentrate together with gold is collected in the separator hopper and they transfer to the final operation the extraction of gold, the remaining elements and compounds located in the ore are sent to the dump, prevent clogging of the slotted injector using sieves and installing a mechanical vibrator with a frequency of 150-250 Hz and an amplitude of up to 2 g on the surface of the injector, providing more selective separation of ore into two fractions is carried out by an adjustable swivel protrusion with a control electric drive.