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 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 Ultrasonic cavitator enhances chemical processes
The Intensive Leaching Units existing in the gold mining industry from reputable 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 actual 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, the main problem in them is not solved - this is the opening and oxidation of refractory gold-bearing minerals. In addition, all these installations do not allow working with finely ground rock 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, bioleaching. Also latest our research shows , no need ultrafine grinding down to 10 microns. Grinding to 25-30 micron is enough with VM for further leaching. Due to fact after processing the total surface of sulphides particles with created microcraters several times higher compare to same sizes get from ball mills .The process of atmospheric oxidation of sulfides occurs without the use of high temperatures, at normal atmospheric pressure and at a medium acidity close to neutral. Unlike other existing sulphide concentrate processing technologies, Flexicone Oxidation technology has a number of advantages:
1.capital and operating costs are lower compared to any other technology
2.No need for pure oxygen, the oxidation process takes place with air
3.the oxidation process occurs an order of magnitude faster than firing
4.the process of fine grinding and oxidation is combined
5.The power consumption is much less than any other technology
6.Scalability allows us to apply our technology from laboratory installations to large-scale gold mining from 1g / t grade
7.100% gold recovery from sulphide concentrates
8. 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 the combined process of grinding and oxidation, the amount of free free gold particles for gravitational extraction is significantly increased, the surface area of minerals is increased and the mechanochemical activation of sulfides, which provides 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 attrition of gold particles is reduced, 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). If further leaching of gold by cyanidation or chloride-hypochlorite method is expected, then the process is carried out in a relatively neutral environment: at a pulp pH of more than 4.0. 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 + 4СаСО3 = 2FeОON + 4СаSO4 ∙ 2H2O + 4CO2 (5) FeАsS + 3,5О2 + 2H2O + CaCO3 = FeAsO4 + CaSO4 ∙ 2H2O + CO2 (6)
Chloride-hypochlorite technology of leaching of 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 makes it possible to operate the system under less corrosive conditions with a 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 in our technology, ultrasonic reactors are used. Unlike 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. The stabilizer is a compound with which chlorine is still active, but is in a more stable form. At high pH, sodium hypochlorite is itself a very weak oxidizing agent in order to cause any significant dissolution of gold. However, in the presence of an activator, this weak oxidizer becomes very effective. For the complete extraction of gold from solution and cake, we developed the FE150 two-chamber electrolyzers with a capacity of 150 kg per load and FE 2500 with a capacity of 2500 kg per load.
Advantages of Flexicone Leaching chloride-hypochlorite technology:
possibility of leaching gold from refractory ores
speeding up 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
low cost of equipment and reagents
Iodine-iodide technology leaching of gold, silver and palladium from ores and concentrates.
We have developed iodine-iodide gold leaching technology in an environment with a pH of 4-9. This technology is universal and makes it possible to operate the system under less corrosive conditions with a lower concentration of iodine. To activate the process of dissolving gold and reduce the consumption of reagents in our technology, ultrasonic reactors and additives are used to activate the process. For the complete extraction of gold from solution and cake, as well as the regeneration of iodine-iodide, we developed the four-cell electrolysers FEI150 and FEI 2500.
Advantages of Flexicone Leaching iodine-iodide technology:
universality of use for most types of ores
possibility of leaching with gold silver and palladium
speeding up the leaching process
leaching in an environment with a pH from 4 to 9
perfect compatibility with the Flexicone Oxidation process
low cost of equipment
low consumption of reagents (from 0.1 kg iodine per ton of ore)
The possibility of using our iodine-iodide technology at negative ambient temperatures makes it unique for the regions of the Extreme North and areas with permafrost
The research results showed that the Flexicone technology makes it possible to efficiently process poor sulphide ores, tailings of processing plants and concentrates with finely disseminated gold at lower operating costs. The Flexicone technology allows for the processing of refractory products with significantly smaller capital investments. Unlike real competitors — autoclave and bacterial oxidation — it does not require the participation of highly qualified specialists; there is no need to create a high concentrate enterprise or a portal for processing concentrates from several objects. Consequently, it is possible to organize local production of small capacity, which will allow to involve in processing medium and small deposits of refined gold, processing of tailings with low gold content. We offer the possibility of using environmentally friendly gravity gold extraction using Flexicone centrifugal concentrators and complete or partial abandonment of the leaching process.