After the primary gold deposit is exposed to the surface, due to the mechanical and chemical weathering, the gold-bearing or gold-bearing parent rock is gradually broken into rock fragments and gold particles. Then, under the action of external force transfer and sorting, minerals with a large specific gravity (such as gold particles) are deposited on the slopes of riversides, riverbeds and lakeshores to form a certain enrichment, which has the value of industrial exploitation. It is called a gold deposit.
Gold deposits are usually mined by gold mining, hydraulic mining, excavation mining and underground (shaft) mining. China's gold-gold deposits are mainly based on gold mining, and there are also hydraulic mining and excavator mining.
The gold ore beneficiation process mainly includes preparation work and sorting operations before the sorting. The preparation work consists mainly of two processes: shredding and sieving. The shattering is mainly to dissociate the ore and clayey slime from the mined ore. Screening is the screening of coarse fractions that do not contain gold. Commonly used equipments include flat screens, cylindrical screens, cylinder scrubbers, and the like. The selection of gold is mainly based on gravity beneficiation. This is because the ratio of sand to gold is large (average 17.50 to 18.0), the grain size is relatively coarse (generally 0.074 to 2 mm), and the other is because the gravity dressing method is economical and simple. . Re-election equipment generally uses various types of chutes, jigs, and shakers (usually used for selection).
Second, the mineral processing method commonly used in the vein gold mine
The various types of gold ore are different in nature, and the ore dressing methods are different. However, re-election, flotation, amalgamation , cyanidation and resin pulping method, carbon slurry adsorption method and heap leaching method are widely used in recent years. Process. For some types of ore, a combined gold extraction process is often used.
There are many options for the gold exchange process used in production practice, and the following are commonly used:
1. Single amalgamation This process is suitable for the treatment of quartz vein primary deposits and oxidized ores containing coarse gold. Mercury amalgamation is an ancient and popular method of gold selection. In the modern gold industry production, the amalgamation method still occupies a very important position. Since gold is mostly in a free state in the ore, a part of the gold particles in various ores can be recovered by amalgamation. Practice has proved that the early recovery of a part of the gold particles by the amalgamation method in the gold selection process can significantly reduce the loss of coarse gold in the tailings.
The theoretical basis for amalgamation is that mercury can selectively wet the gold particles and then diffuse into the wet gold particles.
In water-based pulp, when mercury is in contact with the surface of gold particles, the contact surface formed by gold and mercury replaces the original contact surface between gold and water and mercury and water, thereby reducing surface energy and destroying the barrier gold. A hydrated membrane in contact with mercury. At this point, mercury rapidly diffuses along the surface of the gold particles and reduces the surface energy at the interface. Mercury then diffuses into the interior of the gold particles, forming a mercury-amalgam (mercury paste).
The mercury amalgamation method is divided into two types: internal mixed mercury and external mixed mercury. The amalgamation equipment used has a mercury-mixing plate, a mercury-mixing chute, a skimmer, a mercury-mixing cylinder and a dedicated small ball mill or rod mill.
The process of amalgamation and gold extraction is simple, easy to operate and low in cost. However, mercury is a toxic substance and is very harmful to the human body. Therefore, the concentrator that uses mercury amalgamation should strictly abide by the safety technical operating procedures to minimize the harm of mercury vapor and metallic mercury to the human body.
2. Mercury-re-election combined process This process is divided into two schemes: first remix after mixing mercury and re-electing and then re-allocating mercury. The first remixing process after mixing mercury is suitable for treating simple quartz veins containing gold ore. The first re-selection of the mercury-mixing process is suitable for the treatment of gold ore, but the surface is contaminated with oxide film and is not easy to directly mix mercury ore, and gold ore with low gold content.
3. Re-election (amalgamation)-cyanide combined process This process is applicable to the treatment of quartz vein-containing gold oxide ore. The ore is first re-elected, and the obtained concentrate is re-selected for mercury amalgamation; or the ore is directly mixed with mercury, and the tailings, graded ore, and mixed sand are separately cyanated.
4. Single flotation process This process is suitable for the treatment of sulfide-bearing gold-bearing quartz vein ore and multi-metal gold-bearing sulfide ore and carbonaceous ( graphite ) ore with fine gold particles and high floatability.
5, the amalgam-flotation combined process This process is to first use the amalgam to recover the coarse gold in the ore, mixed mercury tailings for flotation. This process is suitable for processing single ore-treated ore, gold-bearing oxidized ore, and ore associated with free gold. The use of this process has a higher recovery rate than a single flotation process.
6. The whole mud cyanidation (direct cyanidation) process gold is produced in the quartz vein ore in the state of fine or fine particle dispersion. The ore is deeply oxidized and does not contain Cu, As, Sb, Bi and carbonaceous materials. Such ore is best suited for the full mud cyanidation process.
Cyanidation method is one of the main methods to extract gold and silver. Gold extraction in this way has the advantages of high recovery rate, strong adaptability to ore, and real estate gold, so it is widely used.
Cyanide gold extraction consists of four steps: leaching of gold-bearing ore in cyanide solution, separation of gold-containing precious liquid and leaching residue, precipitation of gold leaching and melting of gold mud. The shortcoming of this kind of gold extraction method is that cyanide is a highly toxic substance, which is easy to pollute the environment. In practice, it is necessary to strictly protect and control the environment.
7. Flotation-Cyanide Joint Process This process has the following three scenarios:
(1) Flotation - concentrate cyanidation process. It is suitable for processing gold and sulphide gold-bearing quartz veins close symbiotic ore quartz and pyrite ores.
(2) Flotation-baking-cyanide process. This process is suitable for the treatment of minerals that are free of cyanidation and contain only a small amount of gold.
8. Flotation-re-election joint process This process is mainly based on flotation method, and is suitable for ore which is closely related to gold and sulfide and can only recover gold by smelting method. It is also suitable for gold-bearing quartz vein ore with uneven coarse inlay and higher recovery than single flotation.
9. Heap leaching method is a type of gold extraction by cyanidation method, which is suitable for treating ore with low gold content. The main advantages are simple process, low investment and low cost.
The above nine processes are principle processes and their internal structure should vary depending on the type and nature of the ore being treated.
Regardless of which type of ore, as long as it contains coarse gold, the principle of early harvest and overcharge should be implemented. Before the ore enters the flotation operation, the coarse gold should be recovered in time by re-election, amalgamation or single-slot flotation.
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