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 certain types of ore, a combined gold extraction process is often used.
There are many gold concentrating process schemes for production practice, and the following are commonly used:
1. Single amalgamationThis process is suitable for treating primary quartz vein deposits and oxidized ores containing coarse gold. Mercury amalgamation is an old and common method for gold extraction. In modern gold industry, mercury amalgamation still occupies an important position. Because gold appears mostly in free state in ores, some gold grains can be recovered by mercury mixing method in all kinds of ores. Practice has proved that the loss of coarse-grained gold in tailings can be significantly reduced by using mercury amalgamation method to recover a part of gold grains in advance in the gold separation process.
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 gold and water and the contact surface of mercury and water, thereby reducing the surface energy and destroying the 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 method of extracting gold by mercury amalgamation can be divided into two kinds: internal amalgamation and external amalgamation.
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 Mixing-gravity Separation Joint Process
The process is divided into two schemes: mercury mixing before re-selection and mercury mixing after re-selection. The process of mercury mixing followed by gravity separation is suitable for treating simple quartz vein gold-bearing ores. The process of gravity separation followed by mercury mixing is suitable for the treatment of ores with large gold grains, but not easy to mix directly with mercury and placer gold ores with low gold content, whose surface is polluted and coated by oxide film.
3. Combined process of gravity separation (mercury mixing) and cyanidation
This process is suitable for the treatment of quartz vein gold-containing oxidized ores. The ore is first re-elected, and the refined concentrate is re-elected for mercury amalgamation; or the raw ore is directly mixed with mercury, and the tailings, graded ore, and mixed sand are separately cyanated.
This process is suitable for the treatment of gold-bearing quartz vein ores with fine gold grains and high floatability, as well as polymetallic gold-bearing sulfide ores and carbon-bearing (graphite) ores.
5. Mercury Mixing-Flotation Combined Process
This process is to recover coarse gold from ores by mercury mixing and flotation of mercury-mixed tailings. This process is suitable for treating single flotation ores, gold-bearing oxidized ores and associated ores with free gold. The recovery rate obtained by this process is higher than that by a single flotation process.
6. Whole mud cyanidation (direct cyanidation) process
Gold is produced in quartz vein ore in the form of fine or fine particles dispersed. 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 is one of the main methods to extract gold and silver. Gold extraction by this method has the advantages of high recovery rate, strong adaptability to ores and in-situ production of gold, so it has been widely used.
Gold extraction by cyanidation consists of four steps: leaching of gold-bearing ore in cyanide solution, separation of gold-bearing precious solution from leaching residue, precipitation of gold leaching and smelting of gold sludge. The disadvantage of this gold extraction method is that cyanide is a highly toxic substance and easy to pollute the environment. In practice, we must strictly protect and control the environment.
7. Flotation-Cyanidation Combined Process
This process has three different schemes:
(1) Flotation-concentrate cyanidation process.
It is suitable for treating quartz vein gold-bearing ores and quartz pyrite ores with close relationship between gold and sulfide.
(2) Flotation-roasting-cyanidation process.
This process is suitable for the treatment of minerals containing floatability that are harmful to cyanidation, and only a small amount of gold is bound to this mineral.
8.Flotation-gravity combined process
This process is mainly flotation process, which is suitable for ores where gold and sulphide coexist closely and gold can only be recovered by smelting. It can also be applied to gold-bearing quartz vein ores with uneven distribution and higher recovery than single flotation.
9. Heap leaching method
Heap leaching is a type of gold extraction by cyanidation, which is suitable for the treatment of ore with a lower gold content. The main advantages are simple process, low investment and low cost.
The 9 processes mentioned above are principled processes, and their internal structures should vary according to the types and properties of the ores 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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