| In this paper, the beneficiation of low-grade tin-lead-zinc complex sulfide ore of Dachang of China was studied. The floatation flow was designed, revised, and practical experiments were carried out. Based on the flotation theory of sulfide minerals, the mechanism of sulfide flotation and its practical application was studied.The relationship between pH value and concentration of collector (C) and floatability of three sulfide minerals, which include jamesonite, marmatite and pyrrhotite, were discussed. When butylxanthogenate, dithiophosphate and diethyldithiocarbamate were used as collectors, the result showed that the dithiophosphate has the best flotation effect. When the pulp pH value range is from 3.0 to 7.0, marmatite has well floatability. When the pulp pH value is above 8, marmatite cannot be floated easily. Pyrrhotite has poor floatability. When the pulp pH value range is from 4.5 to 6, pyrrhotite can be floated partly. But when the pulp pH value is above 8, pyrrhotite cannot be floated unless activators are used. The dominant parameters of sulfide mineral floatation system were ascertained.Some novel floatation reagents were selected and many new techniques about the process of grinding, flotation and gravity separation were invented. By the optimization of technique, the novel beneficiation of low-grade tin-lead-zinc complex sulfide ore was invented, which was discussed as following.1) By the gigging-taper-screw gravity separators combination, the multi-staged separation of valuable minerals from low-grade complex sulfide ore was formed. By this method, 30-40% gangue mineral was cast away, the grade of ore was increased, production improved and the cost was decreased.2) Use of composite gravity separators to process low-grade complex sulfide ore containning cassiterite to obtain ores of different grades as gravity separated feeds, and then use different grinding mediums and equipments to process different feeds ofdifferent grades.3) During the process of sulfide ore floatation without middlings, several important parameters including pulp pH value, collectors, flotation time and the flow structure were controlled and adjusted. Use the parallel rougher flotation, subsection adding the different reagents in turn and foam pulp flotation technology instrument can increase the rate of flotation. The efficiency of floatation of sulfide ore can be achieved in the plough floatation with high concentration of the mine pulp, In this way, the consumption of reagents can be reduced.4) Based on the characters of gangue minerals, new disperser and depressor were used. According to different floatability of different size particles, we can strengthen the flotation process. Firstly we can get fine cassiterite of well floatability using fewer reagents. Then more reagents were added to obtain cassiterite of poor floatability. Such was the technology of fine cassiterite floatation.5) By flocculating flotation of ultra fine and low-grade lead, zinc antimony ore, we can reclaim the lead and zinc mineral from the mub with particle-size fraction below 10 u m. Using this technique, the recovery of lead and antimony was enhanced 7%, and the recovery of zinc was enhanced 3%. Every year we can get more 600 tons of tin with grade over 50% by this way.6) Waste water was recycled in the flow. By adding flocculate reagents with high molecular weight in the major flow, the water was purified and recycled. The recycling rate was over 95%.By these research work — novel technology of beneficiation of low grade tin-lead-zinc complex sulfide ore of Dachang, we got excellent economic production indexes: The original grade of metals were: Pb+Sb0.45 %, Zn2.00 % and Sn0.56 %. Their recovery were 71.97 % ,53.41 % and 69.76 % respectively. The production cost was 65RMB per ton.
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