| In the paper, the mineralogy of the lead and zinc "as-mined" ore from Qiandongshan Mine were studied, which included the mineral constituents, the dissemination relationship between intergrowth minerals, the texture of main minerals and single mineral characteristics of lead and zinc. It was confirmed that this has the high grade of lead and the low grade of zinc, the small disseminating sizes and the sample mineral constituents. The "as-mined" ore partially oxidized. So it was of the mixed ore of lead-zinc minerals.The principle technology flow-sheet with lead flotation before zinc flotation used in the original production was affirmed. The main problems existed in the original technology was also clearly pointed out, which included: the grade of Pb in lead concentrate was not high but the grade of Zn slightly high;both the recoveries of Pb and Zn slightly low, the selection of collectors used in lead flotation was less;the amount of middling was more;the flotation time was longer;the flow-sheet was complicated;the equipment was longer;the production cost was high.Under the guidance of the theory relative with electric chemical flotation factors such as the much of grind, the pH value of slurry, flotation time, the consumption amount of lead collectors and frothers were reached in laboratory test;the condition of Pb flotation and Pb-Zn separating flotation were explored;the verifying test of Zn flotation and the experiment of whole closed circuit were carried out. As a result, the corresponding flotation technology conditions were obtained, which were one-stage grinding, high alkaline slurry (pH≥12.5), 2-ethylamine dithiocarbamate replacing butyl aerofloat as Pb flotation collector, the shortened flotation time and the adjusted amount of frother. Compared with the original technology, the modified flotation technology has much shorter time of grinding and flotation.The experimental results indicated that in the flotation system of Pb-Zn multi-metal sulphide ores, the slurry chemical environment of high pH value andlow Eop can improve Pb-flotation, and meantime increase the self -oxidation of sphalerite and pyrite;when pH value is more than 12.5, the recovery of galena reaches up to maximum, at that time, the slurry electric potential Eop is about 170mv;2-ethylamino dithiocarbamate is better than butyl xanthogen and butyl aerofloat as the flotation collector of galena;some lime added in grinder is helpful to stabilize and retain the low electric potential and depress sphalerite, lime and 2-ethylamino dithiocarbamate added in grinder together can improve the beneficiation index of Pb flotation. On the basis of the laboratory experiments, the industrial test was carried out, which incorporated the two flotation sets of original flow-sheet into one flotation set. the technological conditions of industrial test was close to that of laboratory experiment. Through about one month of industrial test, the ideal technical indexes, i.e. the lead concentrate with the grades of 68.83%Pb and 6.12%Zn and the recovery of 88.77%Pb,and Zinc concentrate with the grades of 55.75%Zn and 0.67%Pb and the recovery of 93.98%Zn, were obtained. Compared with original technology, and flotation machines of the modified technology was decreased by 413kw, the production process was more stable and easy to operate, and the capacity of machines was also increased.The industrial test and production practice of more than one year has showed that the application of the floatation adjusted and controlled by electric chemical potential in Qiandongshan Mine is achieved successfully;the net benefit compared with before reforming is increased by Y5.0millions per year. The successful application has a guiding significance for the other Pb-Zn Mines in this local region.
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