Intensive Leaching Units existing in the gold mining industry from well-known suppliers do not recover the claimed 98% of gold from gravity concentrates due to the presence of refractory and finely disseminated gold in minerals (sulfides, tellurides, carbonaceous shales).

As the real practice shows, the real gold recovery is much lower and can be less than 50%. And for flotation concentrates, the use of such installations is generally not profitable, since the recovery on them can be only 25-30%. These installations extract only free gold, they have not solved the main problem - this is the opening and oxidation of refractory gold-bearing minerals. In addition, all these installations do not allow working with finely ground rock of 70 microns and below, since the problem of filtration and obtaining clarified solutions has not been solved.

And the most basic problem of the above installations is cyanide technology, since it is becoming more difficult to obtain a permit for the use of cyanides, and in some cases it is not possible at all.

All of the above disadvantages are solved by us in the cyanide-free Flexicone technology.

 

Flexicone Oxidation Process with Flexicone Oxidation Fe3+ regeneration process

This is the result of our 25 years of research in the field of enrichment of ores and minerals.

Flexicone Oxidation technology combined with the new Flexicone Fe3+ regeneration technology is a combination of fine grinding and oxidation of sulfides without autoclaving, roasting and bioleaching. Also, our latest research shows that there is no need for ultrafine grinding down to 10 microns. Grinding to 25-30 microns in a vortex mill is sufficient for further leaching. This is due to the fact that after treatment, the total surface of sulfide particles with the formed microcraters is several times higher than that of particles of the same size obtained from ball mills. The process of atmospheric oxidation of sulfides occurs without the use of high temperatures, at normal atmospheric pressure and acidity of the medium, close to neutral. Unlike other existing technologies for processing sulphide ores and concentrates, the Flexicone Oxidation technology has a number of advantages.

no need for pure oxygen, the oxidation process is carried out by air

the oxidation process is an order of magnitude faster than firing

the process of fine grinding and oxidation is combined

much less energy consumption compared to any other technology

scalability allows our technology to be applied from laboratory facilities to large-scale gold mining from 1g/tonne

100% gold recovery from sulfide concentrates

the possibility of using only gravity extraction after oxidation and complete or partial rejection of the leaching process.

 

 

Grinding and oxidation of sulfides is carried out in the Vortex Ultrasonic Reactor. At the same time, there is no need for grinding to a fineness of the order of -10 microns, which significantly reduces the energy consumption for grinding and oxidation. In addition, this makes it possible to apply solution filtration in the process of further leaching and abandon the coal-in-pulp technology. This allows the technology to be used for intensive leaching of concentrates, as well as in small-scale production with minimal capital investment.

Due to the use of a combined grinding and oxidation process, the amount of released free gold particles for gravity extraction is significantly increased, the surface area of ​​minerals increases and sulfides are mechanochemically activated, which ensures a high rate of the oxidation process. The physical process of grinding minerals in an ultrasonic reactor is of a resonant-explosive nature, the effect of abrasion of gold particles is reduced in comparison with other methods, and it requires many times less energy spent on grinding.

Due to the active flow of chemical reactions, the pulp spontaneously heats up to a temperature of more than 80°C, but below the boiling point of water, i.e. the process is autothermal. The process of oxidation of sulfide minerals can be described by the following reaction equations: 2FeS2 + 7.5O2 + H2O = Fe2(SO4)3 + H2SO4 (1)

2FeAsS + 5.5O2 + H2O = 2HAsO2 + 2FeSO4 (2)

2FeSO4 + 0.5O2 + H2SO4 = Fe2(SO4)3 + H2O (3)

HAsO2 + Fe2(SO4)3 + 2H2O = H3AsO4 + 2FeSO4 + H2SO4 (4) .

Further leaching of gold by the iodine-iodide or chloride-Fe3+ method is carried out in a relatively neutral environment: at a pulp pH of more than 2.0-8.0. For the neutralization formed during the oxidation of sulfuric acid according to reactions (1) and (4), the cheapest reagent is used - limestone and (or) soda. Thus, in general, the oxidation of sulfides in the process can be described by the following reaction equations:

2FeS2 + 7.5О2 + 9H2O + 4СаCO3 = 2FeООН + 4СаSO4∙2H2O + 4CO2 (5)

FeAsS + 3.5O2 + 2H2O + CaCO3 = FeAsO4 + CaSO4∙2H2O + CO2 (6)

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Flexicone Fe3+ regeneration technology

Unique technology for the regeneration of iron ions Fe2+ into Fe3+

Suitable for sulfide oxidation, non-ferrous metals and gold leaching

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Iodine-iodide technology for leaching gold, silver and palladium from ores and concentrates.

We have developed an iodine-iodide technology for leaching gold in an environment with a pH of 4-9. This technology is versatile and makes it possible to operate the system in less corrosive conditions with a lower iodine concentration. To activate the gold dissolution process and reduce the consumption of reagents, our technology uses KNOWHOW reactors and additives to activate the process. We have developed the FEI150 and FEI 2500 electrolysers for the complete recovery of gold from solution and cake, as well as the regeneration of iodine-iodide.

Our developed filtration system for fine-grained mixtures allows leaching of more cost-effective coal technologies in pulp with less capital investment. In addition, the high stability of AuI solutions, higher gold recovery from the rock and the use of Flexicone filtration technology, makes the technology unique for the application of heap leaching from man-made tailings and off-balance ores with low gold content.

 

 

Benefits of Flexicone Leaching Iodine-Iodide Technology:

universality of application for most types of ores

the possibility of leaching gold, silver and palladium

acceleration of the leaching process at times

leaching in an environment with a pH of 4 to 9

perfect compatibility with the Flexicone Oxidation process

high environmental friendliness

low cost of equipment

solution recirculation

low consumption of reagents (from 0.1 kg of iodine to a ton of ore)

versatility of tank and heap percolation leaching

the possibility of using iodine-iodide technology at low ambient temperatures makes it unique for the regions of the Far North and regions with permafrost

 

Research results have shown that Flexicone technology can efficiently process lean sulphide ores, tailings and finely disseminated gold concentrates at lower operating costs. Flexicone technology allows for the processing of refractory products at a significantly lower capital investment. Unlike real competitors - autoclave and bacterial oxidation - it does not require the participation of highly qualified specialists, there is no need to create an enterprise with a high productivity for concentrate or a portal for processing concentrates from several objects. Consequently, it is possible to organize local production of small capacity, which will make it possible to involve in processing medium and small deposits of refractory gold, processing of tailings with a low gold content. We offer the possibility of using environmentally friendly gravity recovery of gold using Flexicone centrifugal concentrators and completely or partially eliminating the leaching process.

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Chloride-Fe3+ technology for leaching gold from ores and concentrates.

In combination with the Flexicone Fe3+ regeneration technology, we have developed a chloride-Fe3+ technology for gold leaching in a pH 2 environment. This technology makes it possible to operate the system with less toxic and cheap reagents ([NaCl chlorides etc.) and at a cost price can be used as an alternative to bacterial leaching and cyanidation. To activate the process of gold dissolution and reduce the consumption of reagents, our technology uses installations for the intensive regeneration of Fe2+ into Fe3+. Unlike existing chloride-hypochlorite technologies, in our technology the leaching system does not contain expensive additives and stabilizers and consists of NaCl (or another source of chloride) and ferrous iron ions Fe3+ formed as a result of sulfide oxidation. A stabilizer is a compound with which chlorine is still active, but in a more stable form. At high pH, ​​sodium hypochlorite by itself is a very weak oxidizing agent to cause any significant dissolution of gold. However, in the presence of an activator, this weak oxidizing agent becomes very effective. For the complete extraction of gold from solution and cake, we have developed two-chamber electrolyzers FE150 with a capacity of 150kg per load and FE 2500 with a capacity of 2500kg per load.

 

Benefits of Flexicone Leaching Chloride-Fe3+ technology:

the possibility of leaching gold from refractory ores

acceleration of the leaching process by 2-4 times

copper leaching in an environment with pH 2

perfect compatibility with the Flexicone Oxidation process

environmental friendliness

low cost of equipment and reagents