The principle of the zinc powder replacement gold extraction process is to use zinc powder (or zinc wire) as a reducing agent to replace the gold and silver from the leaching solution. Combined with a case of a 300tpd gold project, this article introduces you the whole process of cyanidation-zinc powder replacement for gold extraction.
This project is a gold mine project in Indonesia undertaken by Xinhai mining company. According to the properties of the raw ore and the results of the beneficiation test, Xinhai designed the customized process: the crushing and screening was construction first with a scale of 600t/d, and the grinding and beneficiation are divided in two phases, with each phase of 300t/d respectively. The separation process adopts cyanidion-zinc powder replacement gold extraction process. Let's take a look at the overall beneficiation process.
The raw ore feeding particle size is smaller than 350mm. Following the principle of “more crushing and less grinding”, the crushing stage is designed as a compact and practical two-stage semi-closed circuit process. The final product is 12mm.
The grinding is designed to be ground at both ends. In the first stage of grinding, the grid-type ball mill is used to control the grinding fineness to -200 mesh, accounting for 65%; and the second-stage grinding uses a smooth ball mill to control the grinding fineness to -325 mesh, accounting for 95%.
The combination of pumps and hydrocyclones is used for classification. Compared with the spiral classifiers, the hydrocyclones have some merits including higher efficiency, smaller floor space and other obvious advantages.
The oxidation pretreatment adopts double impeller leaching tank, and the oxidation pretreatment time is 60 hours. After oxidation pretreatment, the pulp is dewatered by the filter press, the dry ore enters the agitation tank for pulping, and lastly the filtrate of the filter press enters the sewage treatment system.
Leaching and washing: The pulp enters the cyanidation leaching process after slurry agitation. The cyanidation leaching time is 48 hours. After two stages of leaching and three stages of washing, the precious liquor is finally obtained from the overflow of a washing thickener.
Zinc powder replacement: The pregnant solution is purified through separating from the solid, washed to remove the suspended solids, deoxidized to remove the dissolved oxygen, and finally come into zinc powder replacement process to get gold mud.
Tailings dehydration stage: A tailings dry discharge workshop is built in the northeast direction of the concentrator to dewater the final tailings of the concentrator. The cyanide tailings enter the tailings dry discharge workshop. The dry discharge of the tailings adopts a box-type open-flow filter press. The dry tailings after pressure filtration are backwashed, and finally the tailings are transported to the tailings pond through a belt conveyor for storage.
Sewage treatment system: The pretreated filtrate enters the two-stage sewage treatment system of thickening and pressure filtration. The trace impurities are discarded and transported to the tailings pond for storage by the belt conveyor. The treated water enters the return pool in the pre-oxidation stage for recycling in the pre-oxidation stage.
After the above four stages, the whole process of replacing gold with zinc powder to recover gold from tailings has been completed. The process effect is ideal. In the first and second phases of the project, the gold leaching rate reaches 89.49%, and the recovery rate is 88.01%.
