Tin-bearing polymetallic sulfide ore is distributed in Guangxi, Yunnan, Hunan, and Guizhou provinces in China. Due to the presence of high-density sulfide minerals such as pyrite, magnetic pyrite, brittle sulfur antimony lead ore, sphalerite, galena, chalcopyrite, etc., in tin-bearing polymetallic sulfide ore, it is often necessary to float and separate sulfide minerals before tin ore reselection.
This article introduces the beneficiation process of a tin-bearing polymetallic sulfide ore through a case study, presenting the magnetic-floatation-gravity combined process.
The ore in question comes from Guangxi and contains copper, tin, and zinc as the main elements of industrial value, followed by sulfur. The low zinc grade poses a challenge in obtaining a high-quality zinc concentrate. Silver and indium can be comprehensively recovered from copper and zinc concentrates.
(1) Grinding
Due to the brittle nature of cassiterite, it is prone to over-grinding, leading to reduced recovery rates in reselection and fine mud flotation. Therefore, the principles of early recovery of coarse grains and staged grinding are commonly employed.
In this case, cassiterite is unevenly distributed in terms of particle size. Grinding experiments show that at the -0.3+0.1mm particle size, the monomer dissociation of tin reaches 70.59%, and at the +0.074mm particle size, the monomer dissociation of tin reaches 91.23%.
Considering the high tin content in the ore, which is the main valuable metal to be recovered, a slightly coarse grinding fineness of -74μm, accounting for 78.70%, is appropriate.
(2) Magnetic separation
The original ore contains a high content of magnetic pyrite, reaching 22.33%. A pre-magnetic separation method using a medium magnetic field (0.5T) is employed to remove the majority of magnetic pyrite, avoiding its adverse impact on subsequent copper-zinc flotation and tin reselection.
To reduce the total content of valuable metals in the magnetic-sulfur concentrate, the magnetic separation closed-circuit process involves one roughing, two scavenging stages, with the magnetic scavenging tailings combined with the magnetic roughing tailings as a flotation feed.
Results of the magnetic separation experiments are shown in Table 5.
(3) Floatation
The floatation section adopts the "priority flotation of copper - sulfur and zinc mixed flotation separation" process.
Priority flotation of copper: Through one roughing, two scavenging, and two cleaning stages, a copper concentrate is obtained. Adding zinc sulfate and sodium sulfite during copper flotation is beneficial for reducing the zinc grade in the copper concentrate.
Mixed flotation of zinc and sulfur: Through one roughing, two scavenging, and one cleaning stage, a mixed concentrate of zinc and sulfur is obtained.
Separation of zinc and sulfur: Adding one scavenging and one cleaning stage to the open-circuit process to improve zinc separation indicators.
The mixed concentrate of zinc and sulfur is subjected to one roughing, one scavenging, and three cleaning stages to obtain zinc concentrate and sulfur-arsenic concentrate. The floatation tailings serve as a reselection feed.
(4) Reselection
The reselection section adopts the "shaking table reselection - middlings regrinding and reselection" process to obtain a reselected tin concentrate. The tin recovery rate is 69.14%.
With the original ore ground to -74μm, accounting for 78.70%, using the "magnetic-floatation-gravity" combined process, closed-circuit tests yielded the following indicators: magnetic-sulfur concentrate with a yield of 16.64%; copper concentrate with a copper grade of 28.65% and a copper recovery rate of 75.59%; zinc concentrate with a zinc grade of 48.37% and a zinc recovery rate of 55.97%; tin concentrate with a tin grade of 50.08% and a tin recovery rate of 52.23%.
Additionally, a low-tin middling with a tin grade of 1.96% and a tin recovery rate of 14.45% was obtained. It is planned to return the tailings for further grinding, which could further improve the indicators. This process is recommended as a basis for design and production optimization.
The above outlines the beneficiation process of tin-bearing polymetallic sulfide ore. Before determining the beneficiation process, representative ore samples should be selected for beneficiation tests. The results of these tests can be used to formulate the beneficiation process, avoiding unnecessary resource waste and achieving higher beneficiation returns.
