| The mixed copper ore in Chuxiong of Yunnan province, China, contains 1.42% copper, with an oxidation rate of 69.10% and a combination rate of 26.09%, the contents of calcium oxide and magnesium oxide in the ore are 10.73% and 2.99% respectively. The ore is very difficult to be treated either by beneficiation or metallurgy due to its high oxidation rate, high combination rate, and high content of acid-consuming gangue minerals. Moreover, the copper minerals are embedded in fine grain size with complex composition in the ore. Many researchers in domestic and foreign universities and research institutes have conducted a lot of research on it since 1980's, no breakthrough, however, was made. At present, the copper ore is mainly separated and processed by hand sorting, followed by flotation for the ore with low oxidation rate, and acid leaching for the ore with high oxidation rate, which results in a copper recovery of 60% to 70%. The ore is so difficult to treat resulting from the above complex natures, small processing capacity and high cost for acid leaching that insufficient utilization of the ore was made until now.Process mineralogy research of the ore, indicated that most of the copper ore embedded in the gangue mineral, and some copper mineral particle size are tiny in a disseminated distribution in the calcium and silicon mud, forming so-called combined copper oxide mineral, which leads to poor floatability and performance of the copper ore.A novel combined process with beneficiation and metallurgy was proposed as "Sulfidization flotation-Intensifying collection-Reverse flotation of acid-consuming gangue minerals-Acid leaching for middlings" based on the characteristics of the ore and lots of tests and theoretical analysis, i.e. recovering copper sulfide minerals and part of easy-to-float oxidized copper minerals by sulfidization flotation; using strong collective reagents or combined reagents to intensify the collecting of difficult-to-float copper minerals in the tailings after sulfidization flotation; transferring the secondary tailings with high content of acid-consuming gangue minerals and high combination rate into reverse flotation to remove the calcium oxide and magnesium oxide; mixed middlings into the acid leaching process to recover the copper minerals. The new process conforms to the nature of the ore, is adaptable for large-scale industrial production.The flotation tests were conducted for the flotation of copper sulfide minerals and part of easy-to-float oxidized copper minerals, and the best flotation flowsheet and conditions are determined as three-stage roughing-rough concentrate regrinding-three-stage cleaning (closed-circuit of middlings returned by turns) through the investigations of grinding fineness, various reagents dosages, stages of rougher and cleaner, as well as regrinding time of rough concentrate. The final copper concentrate is obtained with a grade of 21.53% and a recovery of 51.13%, in which the phase recoveries of copper sulfide ore, free copper oxide ore, and combined copper oxide ore are 86.55%,53.41% and 6.03% respectively.The main purpose of reverse flotation is to remove the acid-consuming gangue minerals. It is, however, very necessary to recover the difficult-to-float copper minerals in the tailings with strong collector before carrying out reverse flotation because part of the copper minerals may lose in the tailings in process of reverse flotation. The reverse flotation was performed using blending collectors with isoamyl xanthate and hydroxamic acid, the middlings with copper grade of 1.02% and recovery of 6.55% was obtained, in which CaO and MgO recovery is about 8%, respectively.There is large quantity of combined copper minerals in the secondary tailings by intensifying collection, the tailings produced in the aforementioned process was treated by reverse flotation to remove the acid-consuming gangue minerals in order to supply good conditions for acid leaching. Oleic acid has proved to be a better flotation collector to recover this copper ore, and there is, so far, no report of utilization of oleic acid in the reverse flotation of copper ore. Oleic acid was employed as collector in reverse flotation to remove the acid-consuming gangue minerals based on the characteristics of the ore, and good results was achieved. The product in the flotation cell is middlings with a copper grade of 0.71%, which is higher than that of tailings grade of 0.53%, and the foam product forms the tailings with the loss of copper recovery of 12.28%. Moreover, good separation of calcium minerals was obtained in the reverse flotation stage with a removal rate of CaO 81.82%, as well as 33.99 percent of the magnesium oxide was removed in the stage.The final flotation flowsheet and conditions were obtained after series of tests, the grinding fineness is 85%-0.074mm, and the flowsheet is three-stage rougher, roughing concentrate regrinding and three-stage cleaner, the final concentrate with copper grade of 21.69% and recovery of 52.52%. The tailings, subsequently, was put into the process of intensifying flotation, and a secondary concentrate was produced in the process. The tertiary concentrate was also produced after the secondary tailings putting into reverse flotation to remove the calcium oxide and magnesium oxide, the blending of secondary concentrate and tertiary concentrate forms the middlings product with a copper grade of 0.85%, and a recovery of 27.18%, the content of calcium oxide in the middlings is decreased by 5.39%. The copper grade in final tailings, is 0.56% and with a lost copper recovery of 20.30%.Such a novel hydrometallurgy process as flash leaching of thick slurry was proposed based on thermodynamic calculation and kinetic analysis of copper leaching in the middlings. The leaching conditions such as dosage of sulfuric acid, leaching time, ratio of liquid to solid and agitation intensity were investigated. A good leaching performance was achieved with a leaching rate of 84.70% under such appropriate conditions as agitation intensity 30m/min, ratio of liquid to solid 2:1, leaching time 30 min, dosage of sulfuric acid 150 Kg per ton of ore, hence one ton electrolytic copper need 17.31 ton sulfuric acid.In a word, a novel combined process with "Sulfidization flotation-Intensifying collection-Reverse flotation of acid-consuming gangue minerals-Acid leaching for middlings" was proposed for Chuxiong copper ore. Satisfied performance was achieved as follows, the copper in final concentrate is 21.69% and the total copper recovery of the whole process is 75.35%. The progress made in this dissertation will supply a good base for high-efficient utilization of the mixed copper ore.
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