Navoi State Mining Institute, Navoi, Uzbekistan:

K. S. Sanakulov, Rector, Professor, Doctor of Engineering Sciences, rektor@ndki.uz

Navoi Mining and Metallurgical Combinat, Navoi, Uzbekistan:

U. A. Ergashev, Head of Engineering Department, Doctor of Engineering Sciences

Engineering Dobersek GmbH, Mönchengladbach, Germany:

A. Dobersek, Chief Executive Officer, Candidate of Engineering Sciences

The modern global market of gold goes through the time of defi ciency of high-quality product. Readily recoverable gold reserves are being gradually depleted, and the processing industry is increasingly more frequently fed with gold which is difficult to extract using conventional techniques. For this reason, it is of the current scientific concern and economic significance to find an efficient technology for such gold recovery. Rebellious ore category includes gold-bearing sulfide ore from the Kokpatas and Daugyztau deposits situated in the Kyzylkum Region of Uzbekistan. The ore features highly variable composition, as well as considerable content of arsenic and carbonaceous matter tightly bonded with sulphides. At this time, ore is processed using a bacterial oxidation plant at deficient gold recovery as against the project. The detailed studies found out that the deficiency was caused by the lack of insight into biocake processing mechanism, which resulted in high loss of recoverable gold. In the studies, some foreign companies were engaged, including Engineering Dobersek GmbH, Germany. The research findings allowed drawing the conclusion that a dedicated approach to oxidizing roasting of biocakes could essentially improve the process performance. It was decided to use a combination scenario in sulphide ore oxidation. At the first stage, flotation concentrate is to be subjected to biooxidation to dissociate sulphide gold as well as to dissolve considerable portion of arsenic and transfer it into solid state in the form of insoluble scorodite (FeAsO₄). After that, the biooxidation product with low arsenic content undergoes oxidation roasting to dissociate carbonaceous gold and to oxidize sulphide sulphur aggregated with carbon. The roasted product is sent to sorptive cyanidation of gold. By the lab-scale testing data, the highest end-to-end gold recovery is reached in oxidation roasting of tailings after sorptive leaching of biooxidation product. The results of the investigation are patented by the patent entity of the Republic of Uzbekistan. At the present time, Navoi MMC jointly with the German specialists from Engineering Dobersek GmbH carry out commercial tests of the technology using modern circulating fluidized bed boilers, with a view to subsequent introduction of the method into industry.

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