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Click to add WeChatRecently, gold prices have continued to rise, constantly setting new historical highs. This is mainly due to the threat of new tariffs, which has further exacerbated market concerns about trade wars and inflation, and market risk aversion has heated up. As a traditional value-preserving tool, gold's demand has risen accordingly, driving up gold prices. For this reason, the gold mining boom continues, and the intensity of beneficiation development has been increased. Effective Gold ore beneficiation methods and equipment are the key to improving gold recovery. This article will analyze it in depth for everyone!
Quartz vein gold ore: Gold is mainly present in quartz veins in the form of natural gold. Gold and quartz are closely symbiotic, but the gold particle size varies, ranging from microscopic gold to coarse gold. The ore grade is relatively high, and it is one of the important ore types for obtaining gold.
Broken zone altered rock type gold ore: mostly formed in fractured zones, the surrounding rock is enriched in the process of hydrothermal alteration, and the mineral composition of this type of gold is complex. In addition to natural gold, it is often accompanied by sulfides such as pyrite and chalcopyrite, and the gangue minerals include sericite and chlorite, and the grade is generally uniform.
Volcanic rock type gold ore: produced in volcanic rocks or subvolcanic rocks, in addition to gold, the minerals are often accompanied by multiple metal sulfides, such as galena and sphalerite, etc., the surrounding rock alteration types are diverse, including silicification, pyrite sericite, etc., and the ore grade varies greatly.
Placer gold ore: It is formed by the weathering, transportation, and deposition of primary gold ore. Gold mainly exists in the form of natural gold particles in loose sandy sediments, such as river sand and beach sand, with coarse particle size and easy to recover.
Gold ore gravity separation is mainly based on the density difference between gold and gangue minerals. Usually, with the help of water flow, centrifugal force and other effects in the gravity field, different particle sizes change their movement trajectory due to different sedimentation speeds, thereby achieving separation. Among the gravity separation methods, the four main ones used are shaking table gravity separation, jigging gravity separation, chute gravity separation and centrifugal gravity separation.
Gold extraction by shaking table: It mainly relies on the water flow and mechanical vibration of the inclined bed surface to separate minerals according to density and particle size. When the slurry is fed into the bed surface, under the combined action of water flow flushing and bed surface vibration, minerals of different densities move in different directions and speeds. Due to the high density of gold, it will move along the bed surface toward the concentrate end, while the gangue will be washed to the tail end by the water flow due to its low density, and finally the mineral separation will be achieved. In terms of gravity separation of gold, the shaking table is mostly suitable for processing particles with a particle size range of 0.03-0.5mm. For some fine-grained gold, further enrichment and selection can also be achieved through a shaking table; for some gold containing multiple metal minerals, gold can be separated from other metal minerals to a certain extent, providing favorable conditions for subsequent comprehensive recovery.
Jigging gold extraction: It uses the periodic pulsation of water flow to stratify the minerals according to density. When the jig is operating, the water flow moves up and down periodically, and then the mineral particles are separated according to the density. The gangue with a smaller density rises quickly and is located in the upper layer, while the gold particles with a larger density rise slowly and are located in the lower layer. At the same time, with the help of the descending water flow, it is quickly discharged through the discharge device to achieve gold enrichment. This method is suitable for processing gold minerals with a particle size range of 0.5-20mm. Whether it is vein gold ore or medium-coarse gold in placer gold ore, it can be effectively separated by a jig.
Chute gold extraction: heavy minerals are precipitated by the gravity of water flow. The slurry flows along the chute under the action of gravity. The gold particles with higher density will be enriched in the trough under the combined action of friction, water flow resistance and gravity, while the gangue with lower density will be discharged with the water flow to achieve separation. This method is suitable for processing coarse-grained gold, especially for gold ore formed in sedimentary environments such as beaches and rivers.
Centrifuge gold extraction: separation is achieved based on specific gravity. Under the action of centrifugal force and other joint forces, the gold particles with higher density settle quickly, while the gangue with lower density remains in the mainstream of the slurry, and then is discharged separately through different discharge ports, thereby achieving effective separation of minerals. This method is mainly suitable for the separation of fine-grained gold ores of 0.03mm and below, especially for gold ores containing mud, which can be better enriched.
Gold ore flotation mainly utilizes the difference in physical and chemical properties between gold and other mineral surfaces. By adding flotation reagents, the surface properties of gold are changed to make it hydrophobic or hydrophilic, and then the flotation is completed with bubbling. Commonly used flotation methods are mainly conventional flotation, preferential flotation, mixed flotation, equal flotation and branched series flotation.
Conventional flotation gold: It is to add reagents to the slurry to adjust the pH value of the slurry, so that the surface of the gold mineral is hydrophobic. When aerated, it will attach to the bubbles and float to achieve flotation. It is suitable for quartz vein-type gold ores with high sulfide content and broken zone altered rock-type gold ores. For gold minerals that exist in a fine-grained and micro-fine-grained state, conventional flotation can effectively achieve monomer dissociation and enrichment.
Preferential flotation gold: If the gold ore contains a variety of minerals with different floatability, the preferential flotation method can be adopted in a certain order to recover the target mineral at one time. Usually, the minerals with better floatability are recovered first, and different minerals are separated at different stages by adjusting the reagent system and flotation conditions. It is mainly suitable for gold ores containing multiple metal sulfides.
Mixed flotation gold: It is to first select multiple useful minerals in the minerals together to obtain mixed concentrates, and then give priority to sorting the mixed gold ore. It is mainly suitable for the situation where the floatability of multiple useful minerals in the ore is similar, and gold and other minerals are closely coexisting and difficult to separate separately.
Equal floatability flotation gold: According to the difference in mineral floatability, minerals with similar floatability are divided into two or more groups, and floated in order from easy to difficult floatability. In the flotation process, by controlling the dosage of reagents and flotation conditions, minerals with similar floatability are floated at the same stage. It is suitable for the situation where the floatability of minerals in the ore is quite different, but there are some minerals with similar floatability.
Branched series flotation gold: The products after grinding and classification are divided into multiple branches, which are floated separately, and then part of the foam products or medium ore of each branch is returned to the previous grinding and classification operation or other suitable operation points to form a branched series process. It is suitable for processing gold ore beneficiation with uneven distribution of embedded particle size and coexistence of coarse and fine particles.
Gold extraction by hydrogenation method mainly uses cyanide solution to dissociate gold, so that gold enters the solution in the form of complex, and then recovers gold from the solution by displacement, adsorption and other methods. Common methods include stirring cyanidation, percolation cyanidation, heap leaching cyanidation, pressurized hydrogenation and biological cyanidation.
Stirring cyanidation gold: The gold particles and cyanide solution are fed into the stirring tank, and they are fully mixed by stirring. The two react chemically to form a soluble gold-cyanide complex, and then the gold is recovered from the solution by solid-liquid separation. During the process, an appropriate amount of protective alkali is generally added to adjust the pH value of the slurry to prevent the loss of cyanide hydrolysis and ensure that the reaction is carried out under alkaline conditions to increase the dissolution rate and leaching rate of gold. This method is mostly suitable for gold extraction from minerals where gold is evenly impregnated in the ore in the form of fine or even micro-fine particles and closely coexists with gangue minerals.
Percolation cyanidation gold: Put the ore blocks crushed to a certain particle size into the percolation tank, and then add the hydrogenation solution to allow the solution to slowly penetrate the ore layer from top to bottom. During the percolation process, cyanide reacts with the gold in the ore, causing the gold to dissolve into the solution and then flow out from the bottom of the percolation tank. The gold is collected and then recovered by desorption electrolysis or zinc powder replacement. This method has a good recovery effect for gold ores with coarse particles and relatively high grades.
Heap leaching gold extraction: Similarly, the ore is crushed to a certain particle size (screening is required to ensure the particle size range) and then piled on the heap leaching site set up in the early stage. Then the cyanide solution is evenly sprayed on the ore pile through the spraying system. The cyanide solution penetrates through the ore pile under the action of gravity, reacts with the gold in the ore, dissolves the gold into the solution, and collects the leaching solution for gold recovery. This method is mostly suitable for processing low-grade (≤1-3g/t) and moderate-grained oxidized gold ores, mainly because the oxidized gold has been weathered and oxidized for a long time, the ore structure is loose, and the porosity is large, which is conducive to the penetration of cyanide solution and contact reaction with gold.
Biological cyanidation gold: Utilize the metabolic action of microorganisms such as Thiobacillus ferrooxidans to oxidize and decompose minerals such as sulfides in gold ore, expose the gold wrapped in it, and then use cyanide solution for leaching. The action of microorganisms can destroy the structure of the ore, increase the contact area between gold and cyanide, and thus increase the leaching rate of gold. It is mostly suitable for processing gold ore containing sulfides such as pyrite and arsenopyrite.
Pressurized cyanidation gold: The ore pulp and cyanide solution are placed in a high-pressure reactor, and the reaction rate and leaching rate of gold and cyanide are increased by heating and pressurizing. High pressure conditions can promote the dissolution of oxygen in the solution, enhance oxidation, and accelerate the chemical reaction between cyanide and gold, shorten the leaching time, and improve the recovery efficiency of gold. For difficult-to-treat sulfide gold ores containing a large amount of sulfides and gold and sulfides closely coexisting, gold can be extracted by pressurized cyanidation. For example, some difficult-to-treat gold containing arsenic and sulfur can obtain better treatment effects.
The above is an introduction to the common methods of gold extraction from gold ore. Under the premise of rapid technological innovation, there are more and more methods for gold extraction. In addition to the above methods, there are also non-cyanide leaching, amalgamation and biological gold extraction. But no matter which method is used, it needs to adapt to the properties of the ore and various beneficiation conditions. If you want to obtain a more ideal gold recovery rate, it is recommended to conduct beneficiation tests and design a suitable gold extraction process through experimental analysis. Xinhai has rich experience in gold selection. It not only has traditional mineral processing technology, but also has made great breakthroughs in the research and development of new processes. At present, it has successfully developed 29 innovative gold selection processes. Xinhai will fully consider the characteristics of each ore and tailor a mineral processing plan for it.
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