FLEXICONE processing technology of refractory ores and concentrates

Our latest advance is cyanide-free technology with 100% gold recovery. For the processing of gold-bearing refractory and sulphide ores and concentrates, Flexicone has developed a unique beneficiation technology.

The technology includes grinding and a fast process of complete oxidation of sulfides without the use of high temperatures and with minimal energy consumption. In addition, there is no need for ultra-fine grinding down to 10 microns.

Flexicone leach technology is particularly suitable for heap leaching where cyanide use is restricted.

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Flexicone Ultrasonic cavitator enhances chemical processes

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

This is the result of our 25 years of research into the beneficiation of ores and minerals.

Flexicone Oxidation technology is a combination of fine grinding and sulfide oxidation 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 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 environment. close to neutral. Unlike other existing sulphide concentrate processing technologies, Flexicone Oxidation technology has several advantages.

no need for pure oxygen, the oxidation process takes place with 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 us to apply our technology from laboratory facilities to large-scale gold mining from 1g / t grade

100% gold recovery from sulphide concentrates

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

 

 

Grinding and oxidation of sulfides is carried out in a vortex ultrasonic reactor. At the same time, there is no need for grinding to a size of about -10 microns, which significantly reduces the energy consumption for grinding and oxidation. In addition, this makes it possible to apply filtration of solutions in the process of further leaching and to abandon the technology of coal in pulp. 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 liberated free gold particles for gravitational extraction is significantly increased, the surface area of ​​minerals is increased and the mechanochemical activation of sulfides, 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 decreases, and in comparison with other methods, it requires several times less energy expended for grinding.

Due to the active course 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 oxidation process 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-hypochlorite method is carried out in a relatively neutral medium: at a pulp pH of more than 4.0-8.0. To neutralize sulfuric acid formed during oxidation by 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 + 4СаCО3 = 2FeОON + 4СаSO4 ∙ 2H2O + 4CO2 (5)

FeАsS + 3,5О2 + 2H2O + CaCO3 = FeAsO4 + CaSO4 ∙ 2H2O + CO2 (6)

Flexicone Leaching Technology

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.

Chloride-hypochlorite technology for leaching gold from ores and concentrates.

We have developed a chloride-hypochlorite technology for leaching gold in an alkaline medium with a pH of 8-8.5. This technology allows the system to operate under less corrosive conditions with lower chloride concentration and can be used as an alternative to cyanide. To activate the process of dissolving gold and reduce the consumption of reagents, ultrasonic reactors are used in our technology. Unlike the existing chloride-hypochlorite technologies, in our technology the leaching system contains an additive of an activator and a stabilizer and consists of 2-5% NaCl (or another source of chloride), 0.1% sodium hypochlorite. A stabilizer is a compound with which chlorine is still active, but in a more stable form. At high pH, ​​sodium hypochlorite itself is a very weak oxidizing agent in order to cause any significant dissolution of gold. However, in the presence of an activator, this weak oxidant becomes very effective. For the complete recovery of gold from solution and cake, we have developed two-chamber electrolysers FE150 with a capacity of 150kg per batch and FE 2500 with a capacity of 2500kg per batch.

 

Benefits of Flexicone Leaching Chloride-Hypochlorite Technology:

the possibility of leaching gold from refractory ores

acceleration of the leaching process by 2-4 times

leaching of gold in an alkaline medium with a pH of 8-8.5

perfect compatibility with the Flexicone Oxidation process

environmental friendliness

low cost of equipment and reagents

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