Gold Extraction from Ores
Intensification of Technology of Gold Extraction from Gold-Containing Complex Ores
Tech Area / Field
- CHE-IND/Industrial Chemistry and Chemical Process Engineering/Chemistry
3 Approved without Funding
VNIIEF, Russia, N. Novgorod reg., Sarov
- Los Alamos National Laboratory / Materials Sciences X-7 Group, USA, NM, Los-Alamos\nDynamic Materials Corporation, USA, CO, Boulder
Project summaryGoal of the Project is development of the methods for intensification of gold extraction from gold-containing polymetal ores.
A gold-containing ore is a chemical-mechanical composition of certain minerals impregnated with gold particles.
The technological procedure of gold extraction from ore consists of the following basic cycles: the preparation cycle (ore grinding), the ore-dressing cycle (washing out of light impurities), and the metallurgical cycle (cyanidation). In particular, cyanidation is gold extraction with use of prussiates solutions. The cyanidation procedure is strongly dependent on minerals containing iron, sulphur, and arsenic. They react actively with cyanic solutions, and cyanidation procedure becomes unprofitable, since iron, sulfur and arsenic are extracted from ore, but not gold.
To increase quantity of gold extracted from ore, the cyanidation procedure is added with chemical catalysts, which are expensive and sometimes hazardous for the environments. There are the methods developed in order to provide preliminary effect on colloidal mixture of fine-dyspersated ore and water (pulp) by constant electrical current, ultrasound, hydroacoustic vibrations.
Purpose of the all above-listed methods is to separate hazardous mineral impurities from gold and to improve efficiency of the cyanidation procedure.
We suggest the method for significant improvement of efficiency of the technology for gold extraction from ore. Advantages of this method comparing to the commonly used technologies is that the suggested method is effective, reliable, relatively simple and rather cheap:
- grinding of ore concentrate for small fractions (hundredth parts of mm);
- separation of mineral fragments, which prevent the cyanidation procedure, from gold parts.
Minerals containing iron, sulfur; arsenic (most hazardous for cyanidation) are extracted by preliminary shock-wave processing of ore concentrate (namely, a pulp that is a mixture of ore and water in volume ratio of 1:4). Before occurrence of chemical reaction of pulp with cyanic solutions, concentrate undergoes shock-wave loading in all volume (explosion of charge of high explosive (HE) placed in a firm metallic casing; electric explosion of special discharger, etc.). Since minerals in the ore concentrate have weak chemical connections, these connections are destroyed due to short-time effect of pulse of high pressure. Separation of gold minerals from impurities is performed by separation of suspension from sediment in pulp).
Further cyanidation will allow to increase the final output of gold from concentrate for several times (as compared to gold output from the same mass of concentrate, but without processing by shock-wave pulse), or to reduce quantity of used expensive and environmentally-hazardous cyanic solutions (with keeping the final output of gold from concentrate at the same level).
As a result of conversion activities, RFNC-VNIIEF experts have got rich experience in development of explosive technologies and introduction of them to industry. For explosive efforts (detonation of high explosives (HE) with weight up to several tens kg), we traditionally use RFNC-VNIIEF buildings and test sites. To record dynamic parameters of short-time processes (detonation characteristics of HE, velocities of plates launching, pressure pulses during their impact, etc.), we constantly use RFNC-VNIIEF equipment-methodical complex.
RFNC-VNIIEF personnel consists of high-skill experts, including researchers – experimentalists, theorists – calculators, chemists – analysts, designers.
In particular, after external pulse effect of increased pressure on gold ore concentrates in the laboratory studies, the further overall chemical analysis revealed decrease of content of hazardous mineral impurities: iron – to 6 times, arsenic – to 6 times, sulphur – to 3 times.
Under the Project frameworks, it is suggested to perform experimental study of the mechanism of shock wave effect on ore concentrate, to develop the scheme of chemical analysis of ore, to develop and suggest design changes in the production line of gold extraction from ore at mining plants. Preliminary calculated evaluations of the procedure will be performed for optimization of experimental efforts. The following aspects will be determined in the experiments:
- response of ore concentrate to shock waves effect of various intensities;
- optimum scheme of chemical analysis of concentrate before and after dynamic effect;
- optimum scheme of shock wave generation (explosion of chemical HE, electric explosion, discharge of pulse laser, etc.);
- designs of units, elements, containers, etc. for introduction of them to the production line of gold extraction from ore at mining plants.
At the final stage, we plan to present a design of a unified line for ore treatment.
The Project activities will help to use the potential of high-skill scientists and engineers involved earlier in weapon development for creation of new advanced industrial technologies. So, the main requirements of the ISTC will be satisfied:
- redirection of scientific potential of scientists and engineers involved earlier in weapon development;
- improvement of level of industrial technologies.
The following problems will be solved under the Project frameworks:
- Review of present status of studies on the problem of intensification of gold extraction from gold-containing ore concentrates.
- Selection of scheme for chemical analysis of concentrate. Justification and verification of techniques for chemical analysis.
- Numerical–experimental studies aimed to select optimum conditions for shock-wave loading of ore concentrate. Results of the studies will be tested by chemical analysis.
- Verification of optimum scheme for generation of shock waves as applied to the production line of gold extraction from ore at mining plants.
- Design verification of units and elements for introduction of them to the production line of gold extraction from ore at mining plants.
- Analysis of results obtained during the Project efforts. Formulation of technology and design of unified line for gold extraction from ore at mining plants.
The program of experimental studies will be discussed and coordinated with the foreign collaborators. It is planned that the foreign collaborators will take part in workshops for discussions of results obtained under the Project frameworks.
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