1 Re-election

Re-election method is based on the relative density of minerals (often referred to as specific gravity) of the differences in the separation of minerals. Mineral particles with different densities in the movement of the medium (water, air and heavy liquid) by the hydrodynamic and various mechanical forces, resulting in suitable loose stratification and separation conditions, so that the different density of mineral particles are separated.

Re-election is one of the common methods for gold separation. In alluvial gold ore, gold is usually in the form of monomer natural gold, particle size is generally greater than 16 tonnes/m3, and the density difference with the vein stone is large, so re-election is the selection of alluvial gold ore is the main, effective and economic method. But in the vein gold, re-election is rarely used alone, not as part of the joint gold extraction process, generally in the grinding and classification circuit, the use of jigger and spiral chute and shaking table with the early recovery of a deconvoluted coarse-grained monomer gold, in order to facilitate the subsequent flotation and hydrogenation operations, and can obtain qualified gold concentrate. This method is more common in small-scale gold mines and local group mining, such as the gold factory in Inner Mongolia Gouliang, Dashuiqing and other gold mines.

The main equipment for re-election of gold is various forms of chute, jigger and shaking table. In addition to conventional re-election equipment, in the digestion and absorption of equipment based on the development of the belt chute, Ross chute, round jig, alluvial gold centrifugal washing unit and other new re-election equipment, in gold production to achieve good results. In alluvial gold mines commonly used amalgam method to separate gold and heavy sand minerals; and in the vein gold mines, amalgam is usually used as part of the joint process with flotation, re-election, cyanidation, etc., mainly used to capture coarse-grained monomer gold.

1) Jigging method

Jigging is a gold selection process using jigging machine as the gold selection equipment. Jigger is commonly used re-election equipment, there are many types.

The working principle of diaphragm jigger is: when the eccentric drive mechanism drives the diaphragm for reciprocating motion, the water in the jigging chamber will be through the vertical alternating pulsating water flow produced by the screen. The selected materials are given to the top of the bed, and the bed ore and water form the particle group system. When the water flow upward impact, the particle group was loose suspended state, at this time the light weight of different sizes of ore particles to different speeds of settlement, large density coarse particles (bedrock) settled in the lower layer. When the water flow down, produce inhalation effect, the density of large particle size of small ore particles through the bed gap into the lower layer.

2) Shaking bed gold separation method

Shaking bed gold separation method is to shake the bed as the main equipment for the gold selection process. Shaking bed is in the horizontal media flow for ore dressing equipment, by the bed and transmission mechanism of two parts, bed by the transmission mechanism with action longitudinal reciprocating motion. Ore in the shaking bed sorting is in the bed reciprocating movement process is completed gradually. Factors contributing to the movement of the ore particles, in addition to their own gravity, mainly is the impulse flow and bed surface differential motion. Ore particles in motion perpendicular to the bed stratification and parallel to the bed separation. The result of the two roles is different ore particles from the bed surface of the different zones of discharge.

Shaking bed according to the selection of other ore particle size difference, can be divided into coarse sand bed (> 0.5 mm), fine sand bed (0.5 ~ 0.074 mm) and mud bed (0.074 ~ 0.037 mm) three kinds.

3) Chute gold separation

Chute gold separation is a kind of re-election method. The main equipment of the chute gold separation is the chute. Chute is an inclination angle of 3 ° ~ 4 ° (not more than 14 ° ~ 16 °) of wood (or steel) narrow inclined trough. In the gold industry, they can be manufactured in situ. Separation principle is: the slurry from the head of the chute into the chute, in the water flow force, gravity (or centrifugal force), ore particles and the bottom of the chute between the friction and other forces under the joint action of the different density of the ore particles loose stratification and separation, the density of the large at the bottom of the chute to become a concentrate, the density of the small to become the tailings. Chute for intermittent operation, when the bottom of the trough concentrate deposited to a certain height, stop giving ore, clear out the concentrate.

The chute is divided into coarse sand chute and slime chute, the former is suitable for processing coarse-grained materials, the latter is suitable for processing fine-grained materials. The bottom of the coarse chute is equipped with pavement and baffle.

Coarse chute is the main equipment for alluvial gold ore dressing, which is used on land and gold mining ship. The big chute on the land is generally about 15 metres, and the one on the gold mining ship is generally 4-6 metres.

4) Spiral concentrator gold processing method

Spiral concentrator gold processing method is to spiral concentrator as the main equipment for gold processing. Spiral concentrator is the use of gravity, friction, centrifugal force and the combined effect of water flow, so that the ore particles according to the specific gravity, particle size, shape separation of a kind of inclined chute concentrator. The whole inclined chute bends into a spiral in the vertical direction. The sorting process is: the slurry fed from the top of the inclined chute flows downward in a spiral line along the inclined chute. In the flow process, the ore particles are stratified. Large particles with small density are distributed at the outer edge of the spiral chute, and fine particles with large density are distributed at the inner edge of the spiral chute. After stratification, the heavy products are discharged from the discharge port at the bottom of the inner chute using the interceptor, while the light products are discharged from the end of the spiral chute.

Spiral concentrator simple structure, easy to manufacture, no transmission mechanism, no power; selection of more than 6 mm, 0.05 mm or less and contains flat vein material effect is poor.

5) Cone concentrator gold separation method

Cone concentrator is based on the principle of the evolution of the tip shrinkage chute (also known as fan-shaped chute). Shrinking chute is fan-shaped, slot length of about 1 metre, to the end of the 125-400 mm wide, the discharge end of the 25-9 mm wide, the slot surface is placed at an angle.

2 Amalgamation method

Amalgamation method can be divided into internal amalgamation and external amalgamation according to its production method. In alluvial gold mines commonly used amalgamation method to separate gold and heavy sand minerals; in the vein gold mines, amalgamation is usually used as part of the joint process Hu with flotation, re-election, cyanidation, etc., mainly used to promote the capture of coarse-grained monomer gold.

Internal amalgamation is carried out in the amalgamating cylinder or mill, which can better control mercury pollution.

The main equipment for external amalgamation is mercury amalgamating plate, which is composed of three parts: bracket, bed surface and mercury plate. The material of mercury plate is made of purple copper plate, silver-plated copper plate, mercury plate, etc. The mercury mixing effect of silver-plated copper plate is good. In order to silver plating and production replacement convenience, often the electrolytic copper plate cut into 400 ~ 600 mm wide, 800 ~ 1,200 mm long small pieces, silver plating, according to the bracket of the inclined direction of a piece of the bed laid on the surface.

The determination of the area of the mercury plate is related to the amount of ore to be processed, the nature of the ore and the role of the amalgamation operation in the gold beneficiation process. Usually, in the mercury plate on the surface of the slurry flow depth of 5 to 8 mm, the flow rate of 0.5 to 0.7 m / s conditions, processing a ton of ore required for the mercury plate area of 0.05 to 0.5 square metres / tonne - day. If the amalgamation is only to capture large particles of free gold, and its tailings still need flotation, re-election and cyanidation, the public office quota can be set at 0.1-0.2 square metres / tonne. Day.

Mercury amalgamation operating conditions: feed concentration of 10 to 25%, feed particle size of 3 to 0.4 mm, slurry flow rate of 0.5 to 0.7 m / sec. Mercury consumption is 3～8g/tonne.