Vein gold, is also known as lode gold, there are many types of vein gold ore, which can be summarized as gold-bearing quartz vein or gold-bearing pyrite quartz vein gold ore; gold-bearing pyrite granite type; gold-bearing polymetallic sulfide ore quartz vein type; gold-containing oxidized ore quartz vein type and gold-containing tungsten-arsenic ore quartz vein type.
According to the characteristics of each type of ore, vein gold beneficiation processing methods include gravity separation, amalgamation, flotation, cyanide, the carbon in pulp and resin adsorption.
1 Gravity separation
Gravity separation is one of the oldest and most common gold extraction methods. In the placer gold deposits, the density of gold is generally greater than 6t/m3, which is different from the density of gangue. Therefore, the gravity separation method is the most important, effective and economical method for gold mining.
However, it is rarely used alone in the vein gold processing plants, more often combines the jigging machine, shaker table or spiral chute to recover the coarse gold. That is beneficial to improve the flotation and cyanide effect.
Main gravity separators: spiral chute, mineral jig, shaker tables, centrifugal concentrator, etc.
The amalgamation method can be divided into internally mixed mercury and externally mixed mercury according to its production mode. In the alluvial gold deposit mining, mercury is widely used to separate gold and heavy sand minerals. In the vein gold mine, amalgam is usually used as part of the combined process with flotation, gravity separation, cyanidation, etc., for the capture of coarse monomers gold.
The internal amalgamation is carried out in a mercury amalgamation tank or a grinding machine, which can better control the pollution of mercury.
The main equipment for external amalgamation is a mercury-mixing plate, which consists of a bracket, a bed surface and a mercury plate. The mercury plate material various in copper plate, silver-plated copper plate, sterling silver plate, etc., and the silver-plated copper plate has the best mercury-mixing effect. In order to facilitate silver plating and easy replacement in production, the electrolytic copper plate is often cut into small pieces of 400-600 mm in width and 800-1200 mm in length, and after silver plating, the blocks are laid on the bed surface in the oblique direction of the bracket.
3 Gold flotation
Flotation is one of the most widely used methods for processing lode gold ore. In most cases, the gold flotation method has the best effect in the sulfide mineral ore containing gold. Flotation can not only maximize gold enrich into sulfide mineral concentrates, but also treat tailings.
The flotation process is also used to treat polymetallic gold-bearing ores such as gold-copper, gold-lead, gold-bismuth, gold-copper-lead-zinc-sulfur ore. For this type of ore, the flotation process can effectively select various gold-bearing sulfide concentrates, which is conducive to the comprehensive recovery of mineral resources.
In addition, the refractory ores that cannot be directly treated by amalgamation or cyanidation are also required to be treated by a combined process including flotation.
Of course, the flotation method also has limitations; for coarse-grained inlays, ores with a gold particle size greater than 0.2 mm, and for quartz-bearing gold-bearing ores without sulfides, it is difficult to obtain a stable flotation foam after slurrying, thus not suit for using flotation.
In recent years, the flotation process of gold ore has made great progress, mainly in the innovation of process, the development of new agents, and the improvement of design. The use of stage grinding and stage selection process is the current development trend of flotation gold selection. Most foreign gold selection plants use two or even three sections, and the recovery rate of gold is increased by 2% to 6%.
Because the flotation method can only maximize the concentration of gold into various sulfide mineral concentrates, and can not finally obtain the finished gold, therefore, there are only a few gold selection plants using a single flotation process, generally the flotation is used as a joint. A process of the process is adopted. At present, China’s gold selection plants using a single flotation process include gold mines such as Suichang and Xiuyan, as well as small gold mines in some local groups.
Since the cyanidation process was applied to the gold and silver mines in 1887, it has a history of nearly one hundred years. Because of its high recovery rate and strong adaptability, it is still one of the main methods of gold production.
The cyanidation process can be divided into agitating cyanidation and diafiltration cyanidation. Stirring cyanidation for treatment of re-election, mercury-mixed tailings and flotation of gold-bearing concentrates, or for full mud cyanidation; and diafiltration cyanidation for treatment of flotation tailings and low grade gold Heap leaching of ore. The conventional cyanidation process is a very mature process, which includes preparation of leaching raw materials; stirring cyanide leaching; countercurrent washing solid-liquid separation; leaching liquid purification and deoxidation; zinc powder replacement and pickling; and smelting ingots and the like.
5 Cyanide carbon in pulp (CIP)
The CIP process is a new technique for recovering gold and silver after developing based on conventional cyanide leaching and zinc powder replacement. It is mainly composed of leaching raw material preparation, stirring leaching and countercurrent carbon adsorption, gold loaded carbon desorption, electrowinning or deoxidizing zinc powder replacement, smelting ingots and regeneration of activated carbon.
6 Heap leaching
Heap leaching is the transfer of the mined ore to a pre-prepared yard to pile up, or directly on the stored waste rock or low-grade ore, using cyanide leaching solution for spraying or diafiltration, so that the solution passes through the ore. The percolation leaching action is generated, the cyanide leaching solution is circulated several times, the ore heap is repeatedly sprayed, and then the leachate is collected, and then treated by activated carbon adsorption method or metal zinc replacement method. The gold grade of the ore treated by the heap leaching method in foreign countries is generally 1~3g/t, the recovery rate of gold is 50%-80%, and the recovery rate of silver is 30%-50%.