Research On Mineral Processing Of An Oxidized Gold Ore Of Ganzi

Mineral resources are the basic materials of survival and development of humansociety. Gold has the dual natures of currency and commodity, it is not only a kind ofmineral resource, but also a special commodity.It has been listed by countries asimportant strategic resources for a long time. In the rapid development of economy, andthe progress of science and technology, gold is the important factor of the decision ofacountry’s international status, economic development and social stability.However, as aconsequence of lacking high grade gold ores, there is a serious shortage of goldresource at present in China. Additionally, refractory gold ore is accounting forone-third of the total gold resources in China, thus the study of refractory andcomplicated gold ore has always been significance and urgent, especially thetechnology of extracting these ores.The gold ore in Ganzi, Sichuan province, was an original sulfide ore, in whichthe Au primarily occurred in the pyrite. A flotation process of “One-rough, Two-fine,Two-sweep” was used by the former ore processing plant, and a concentrate holdingthe gold grade of80g/t could be obtained with a recovery rate of80%. Nevertheless,the former technology is not suitable for nowadays condition, because of the changeof the ore body as well as the ore characteristics with the exploitation, which led to anincreasing in degree of oxidation. For the sake of investigating the beneficiability ofthe ore, a detailed and systematical study on the characteristics of the ore was carriedout in this thesis. The results of the study can provide technological references for theexploitation and utilization of the ore, as well as the experimental information for theevaluation of the deposit, and the industrial indicators.It demonstrated that the Au content was5.63g/t, S0.29%, As0.56%and Fe8.92%(in weight percent), in which Au was the only composition worth recovering inprocessing mineralogy study. The major metallic minerals in the ore were limonite,pyrite and arsenopyrite, while the major gangue minerals were quartz, illite, diopsideand kaolinite. Gold possessedthe proportion of the total gold74.78%inlimonitefollowed13.14%in sulfide,respectively.Due to the high degree of oxidationof the ore, it belonged to the typical gold ore which held84.20%of the total gold. The difficulty of processing and smelting will increase tremendously owing to thefineness of gold particles, the easiness of argillization of gangue minerals, and thehigh content of Arsenic.Flotation, gravity separation, magnetic separation and cyanide leaching wereincluded in the beneficiation experiments according to the ore characteristics and theoccurrance of Au. And the “Cyanide leaching-Tailings gravity separation”combined process was determined based on the different results concluded fromvarious experimental plans.Ultimately, the recovery rate of gold leaching could reach76.55%when the-74μm particles accounted for95%, the addition of CaCO3were1000g/t, NaCN750g/t, the solid-to-liquid ratio was2:1and the leaching time was36hours accordingto the optimalization experiments.Gravity separation of tailingshave been carried out on the basis of cyanideleaching experiments. The direct shaker gravity separation process of tailings waschoosen compared to the regrinding and reconcentration. Based on the analyses ofthemineral composition and distribution ofthe gold tailings, anefficient Falcon centrifugewas choosen to scaveng the shaking table tailings, and the effect of centrifugal forcefield on the gold recovery rate was investigated.The gold concentrate (35.63g/t and31.82g/t)could be obtainedthrough the direct shaker gravity separation and sweepcentrifuge process. By this means, the gold recovery rate increased by19.15%, thegrade of tailings reduce to0.25g/t.The gold recovery rate can reach95.7%using the “Cyanide leaching-Tailingsgravity separation” combined process to deal with the oxide gold ore, by which theseores can be utilized efficiently.