| Cassiterite is one of the advantageous mineral resources in our country. China is also the largest tin producer and consumer in the world. With the exploitation of tin resources year by year, tractable tin resources are becoming less and less, which makes people begin to pay attention to the development and utilization of low-grade refractory tin resources. In this thesis, bamei lead-zinc-tin polymetallic ore in Yunnan was chosen as research object. A detailed process mineralogy research was carried out, and tin beneficiation process, on the basis, was mainly conducted in deep researches.Process mineralogy research results showed that the valuable elements in the ore are mainly zinc, lead, tin, and silver. Metallic minerals are mainly pyrite, pyrrhotite, galena, sphalerite, marmatite, cassiterite, and gangue minerals are mainly quartz, feldspar, calcite, muscovite, dolomite, etc. The tin in the ore is mainly in the form of cassiterite in which the distribution rate of tin metal is 89.75%. Many factors increased the difficulty of the separation of cassiterite, such as fine particle size of cassiterite process (crystallization), low monomer dissociation degree of cassiterite in the coarse grinding fineness, dispersed distribution of tin, etc.On the basis of researches on ore properties, lead and zinc in the ore were recycled before tin sorting, and "priority floating lead-zinc re-election" process was chosen. During lead sorting operation, lime, sodium sulfite+zinc sulfate and ethyl xanthate were chosen as pH regulator, inhibitor and collector, respectively; during zinc sorting operation, copper sulfate and ethyl thio carbamate were chosen as activator and collector, respectively. Lead concentrate assaying Pb 40.92% and Ag 1610.53 g/t at the recoveries of 81.25% and 77.03%, respectively; zinc concentrate containing Zn 43.23% with the recovery of 85.92% were obtained.The main purpose of this study was to recover tin from tailings of zinc flotation. "Re-grinding desulfurization-tin recovery" treatment scheme was put forward after many exploratory experiments. Sulfur concentrate with a grade of 42.57% at the recovery of 82.47% can be obtained and, at the same time, tin rough concentrate with a grade of 32.65% at the recovery of 59.03% and low-grade tin middling with a grade of 0.69% at a recovery of 5.02% can be preliminary obtained. In order to improve the grade of tin rough concentrate, "weak magnetic separation for iron removal-flotation enhanced desulfurization" process was adopted to treat tin rough concentrate. Under the conditions of weak magnetic field strength 1400 Oe, pulp concentration of flotation enhanced desulfurization 24.76%, combined collector 20g/t and 2# oil 10g/t, eventually tin concentrate with a grade of 42.38% at the recovery of 58.57% can be obtained.The test results showed that adopting "priority floating lead-zinc re-election-re-grinding desulfurization of tailing of zinc flotation-gravity separation sorting tin-weak magnetic separation iron removal of tin rough concentrate-flotation enhanced desulfurization" combined process to treat lead-zinc-tin polymetallic ore, which not only obtained qualified tin concentrate but also acquired an increase of total recovery of tin by 20%～30% compared to the current production index. The experimental research provides reference and basis for actual production, development and utilization of similar tin resources for mill plant. It is of great significance for achieving comprehensive development of low-grade lead-zinc-tin polymetallic ore.
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