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Gold ore flotation is a commonly used process in gold beneficiation plants. It is mainly suitable for processing gold ore with finer particles, sulfide gold-bearing quartz vein ore with good floatability, and processing polymetallic gold-bearing sulfide ore and graphite-bearing gold ore ores.
In the production process, the general gold flotation process mainly includes crushing and grinding, separation and dehydration.
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The effective recovery of gold mainly depends on the mineral properties and the particle size distribution. Therefore, crushing and grinding are very important. The raw ore enters the crusher for crushing and then enters the vibrating screen for screening. The upper product is crushed together with the middle product after the second crushing. The two crushed products are screened again. The classifier forms closed-circuit grinding. After classification, the grinding products enter the second-stage ball mill for regrinding and then form closed-circuit grinding together with the cyclone. For gold sulfide minerals with good floatability, the monomer can be dissociated by grinding to 60~80%-75μm.
In the crushing and grinding process, the jaw crusher is mostly used for coarse crushing, the cone crusher is used for medium or fine crushing, and the ball mill equipment is mostly used in the grinding stage. The grid ball mill does one stage of grinding for rough grinding, and the overflow ball mill does two stages of grinding for fine grinding.
Flotation gold separation is mainly based on the difference in the physical and chemical properties of the surface of mineral particles and the difference in the floatability of the minerals. The commonly used flotation processes mainly include the single flotation process, flotation-gravity process, flotation-concentrate cyanidation process, flotation-roasting-cyanidation process, and so on.
Single flotation is to first float gold into copper and lead concentrates and then extract gold from these concentrates, so it is an economical and reasonable process for gold ore containing non-ferrous metals in the original ore. Single flotation can not only enrich gold into sulfide minerals as much as possible but also realize comprehensive utilization of polymetallic. However, the final product gold cannot be obtained, and it is often combined with other beneficiation methods to form a combined process.
In the separation process, the commonly used flotation equipment is mainly mechanical agitating flotation machine (SF type, JJF type, BF type), aerated agitated flotation machine (XCF type, KYF type), and flotation column. Among them, SF type, JJF type, and XCF type are suitable for roughing and sweeping processes, KYF type, and BF type are suitable for roughing and selection processes and the flotation column is mainly suitable for gold minerals with fine particle size and low density. It is less used in rock gold mines.
In this process, the flotation concentrate is obtained from the raw ore by flotation separation, and the sulfide part in the flotation tailings often exists in the form of conjoint with the gangue. In addition to being encapsulated in sulfide by submicroscopic fine particles, gold often exists as coarse-grained and fine-grained single gold. Coarse-grained sulfide and gangue conjoined bodies and coarse-grained natural gold in tailings are difficult to recover by flotation, and part of the gold can be better recovered by gravity separation.
In the floating-gravity combined process, the commonly used gravity separation equipment is mainly: jig, shaking table and spiral chute, etc. Among them, the jig is suitable for minerals with a particle size of 30 (20) ~ 0.5mm, and the shaking table is suitable for smaller particle sizes. For fine mineral sorting, the chute is suitable for sorting gold ore with a particle size of 0.3-0.03mm.
In this process, xanthate is generally used as a collector, pine alcohol oil is used as a foaming agent, and the gold concentrate is obtained from the weak alkaline pulp by flotation in the flotation machine. Then the flotation concentrate is cyanided and leached, the gold is dissolved by cyanide, the complex enters the solution, and then replaced with zinc powder to obtain gold mud, and finally, the gold mud is pyro-smelted to obtain pure gold.
In the flotation-cyanidation process, the gold mine cyanidation equipment mainly includes desorption electrolysis and zinc powder replacement devices, and other auxiliary equipment also includes washing thickener, leaching agitator tank, air lifter, carbon screen, depositing tank, etc.
For the flotation concentrate with high arsenic and sulfur content, after the cyanide tailings are floated, impurities such as sulfur, iron, and arsenic are enriched into the concentrate to become a refractory high-sulfur and high-arsenic concentrate, which cannot be directly cyanide. During chemical leaching, the flotation gold concentrate can be oxidized and roasted first to remove arsenic and sulfur, so that the calcined structure after roasting is loose, which is more conducive to the leaching of gold and silver.
General gold mine dewatering processes include concentrate dewatering and tailings dewatering. Concentrate dewatering needs to be determined according to the process used in the concentrate process. The process mostly adopts the concentration and filtration dewatering process. For tailings dewatering, a suitable dehydration process is customized according to the properties of tailings slurry.
Dewatering equipment commonly used in the dewatering process includes thickeners, filter presses, cyclones, etc. Among them, thickeners can be used for one-stage dewatering of refined and tailings, and can also be used for concentration or leaching washing before leaching in cyanide plants. Cyclones and filter presses are mainly used for the tailings dewatering process.
The above is the introduction of the gold ore flotation process and related equipment. However, not all gold ores are suitable for the flotation process, and the gold resources are very precious. In order to select the ores more reasonably, the beneficiation process is very important. In order to select gold from gold ore in a more economical and environmentally friendly way, an experimental analysis of the ore should be carried out first, and a beneficiation process that suits the situation should be customized through a scientific and reasonable test report to achieve an ideal return on investment.