| Gold, silver and iron have been the main resources of national strategic economic reserves, and have been widely used in bijouterie industry, construction and modern high-tech fields. The Beiya gold mine in Heqing county, Dali municipality of Yunnan province is the largest Au-Ag-Fe oxidized deposit in southwestern China. Since its commericial operation, the concentrator has invariably adopted a combined process of "fine grinding-cyanidation-magnetic separation" to recover gold, silver and iron. In order to improve the processing performance, Several key technologies both in fundamental research and industrial application were developed, which is expected to be a significantly practical operation to alleviate such resources shortage.Process mineralogy indicated that the raw ore contained 1.91g/t Au,41.20g/t Ag and 35.17% Fe, and could be defined as a low grade Au-Fe paragenic ore associated with Ag. The raw ore contained 0.40% Cu, in which the valuable minerals were mostly in the forms of iron-combined oxides, but some free oxides such as malachite were worthy of attention to be recovered. The raw ore contained 1.18% Pb, in which the lead was mostly in the forms of plumbojarosite, and coud not be recovered currently. The raw ore also containd 1.76% Mn, and coronadite and psilomelane were the major manganese minerals. Besides, according to the size distribution analysis, the cumulative yield of ultra-fine particles (-10μm) was up to 18.07%, and the raw ore could be classified as a high-slime resource. Moreover, the gold/silver, limonite/manganese, and magnetite/maghemite were ultra-finely, medium-finely and coarse-medium disseminated in the ore, respectively.Based on the gold texture, this thesis focused on the preg-robbing of gold by clays and copper dissolution during cyanidation. Evidence for the adsorption or re-precipitation of gold from cyanide solutions onto clay minerals was conclusive, and the correlation coefficients calculated by Spearman rank correlation formula indicated that adsorption contributed to the total gold loss from the overgrinded limonite and dolomite clays. For copper dissolution, free cyanide ion concentration could be an indicator to determine whether there was copper dissolved in cyanide solution. Maintaining the free cyanide ion concentration lower than 1.0g/L could prevent copper dissolution, and Au leaching rate could reach a high level around the free cyanide ion concentration of 0.8g/L. Thus, controlling the free cyanide ion concentration ranging from 0.8 g/L to 1.0 g/L could realize the selective leaching of gold.According to the X-ray plane scanning results, most of the silver grains were disseminated in or bound with the manganese oxides, and the surrounding manganese mineralization rendered this metal inaccessible to cyanide. In order to destroy the locked lattice structures, the leaching mechanisms of manganese minerals were discussed. The thermodynamic analysis results indicated that manganese could be dissolved in strong acid solution with the pH of lower than 3.62, and reductant was required to adjust the pulp potential to less than 1.2295V. At room temperature, iron scrap was selected as reductant, and the reaction equilibrium constant was up to 1052, which proved completed dissolution of manganese minerals, and the overall redox reaction could be deduced as:3MnO2+6H2SO4+2Fe=Fe2(SO4)3+3MnSO4+6H2O. The dynamics analysis results indicated that the dissolution of manganese minerals was dominated and controlled by internal diffusion steps, and the kinetic equation could be deduced as:1-2ε/3-(1-ε)2/3= 0.12171K0r0-2C10.13227C20.13727t. Besides, the differences of leaching behaviors between gold and silver were also discussed. Electrochemical analysis results indicated that an obvious ordinal character of "first gold then silver" during cyanidation was conclusive, and dynamics analysis results then indicated that the gold leaching velocity mainly depended on the oxygen concentration of cyanide solution. Thus, in order to improve the gold dissolution rate and save time for silver leaching, an assisted reagent BY-2, which was mixed in certain ratio by two common peroxides, was introduced in this thesis because of its incredible ability to release oxygen. Moreover, for gold and silver in cyanide solution, adsorption tests by activated carbon were conducted, and the coadsorption behaviors of gold and silver was a two-stage process:first Au and Ag were adsorbed by activated carbon optionally, then the adsorbed Ag was replaced by Au due to its lower adsorption activity, and that was the primary cause of the low silver absorption rate.For iron minerals, as the grinding fineness increased, the yields of the overgrinded grains were increasing, and the magnetic separation tests results showed a significant decline in iron recovery, and this was taken as proof that the fine grinding process used in Beiya concentrator was the main course of the low iron recovery. Besides, other major minerals also showed obvious enrichment characteristics during magnetic separation. Malachite could be enriched in weak-magnetic minerals due to its close relation with limonite under coarser grinding fineness, and dolomite could be discarded to non-magnetic products under any grinding fineness.Based on the above study, a series of magnetic separation and leaching tests were conducted, and a novel idea of "coarse grinding-classified by magnetic separation-leaching separately" was proposed. Firstly, under coarse grinding fineness, magnetic separation was the first step to classify the minerals into strong-magnetics, weak-magnetics and non-magnetics, which could prevent the formation of new slimes and overgrinded grains from the beginning. Then, according to the property of each group, "regrinding-cyanidation", "reductive sulfating leaching-cyanidation-magnetic separation" and "direct cyanidation" were finally adopted for strong-magnetics, weak-magnetics and non-magnetics, respectively, and the results showed that Au leaching rate of 93.05%, Ag leaching rate of 74.34% and iron recovery of 70.86% could be obtained, which realized the comprehensive utilization of the Au-Ag-Fe resources.Some industrial application has already been sucessfully adopetd in the Beiya concentrator without changing the process structure, and practice results indicated that the leaching rates of gold and silver increased to 93.09% and 36.91%, respectively, and the iron recovery increased to 51.30%. For the novel process of "coarse grinding-classified by magnetic separation-leaching separately", there were two obstacles:the settling problem of each group and the safe production problem of adding sulfuric acid. In order to solve above problems, settling tests of each group and adjusting tests from alkalinity to acidity of cyanide-containing pulp were conducted respectively, and a industrial flowsheet of the novel process was then suggested.
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