| Tin metal is very improtant for human being's lives and activitivs.It plays a very important role in many areas as national economy and defense. Gravity concentration is a tranditional method for tin recovery. However, with the reduction of tin ore grade, more complex tin ore typies and association of multi-metals, its benification method has became more various from single process to many other combined technologies. They have been developed to recovery more valuable metals rather than tin only, avoiding waste of resources. Especially, it has been known that the tin recovery of fine and ultra fine particles in tailings is a big problem under present technological conditions.According to company's requirements, research on optional benification for a tin skarn ore in SiChuan province is carried out, in order to find out a reasonable process to obtain possible grade and recovery of tin concentrate, making technical basis for next pilot test.Referring to various literatures and different data of cassiterrite concentration at home and abroad, and combining pratice of tin concentration plants in China, a lot of laboratory tests are carried out. The investigation results of process mineralogy properties show that grade of the tin skarn ore sample is only 0.48%, with 11.03% Fe and 62.84% SiO2. The results of mineral phase analysis illustrate that tin metal exists in cassiterite at a high content of 96.64%, others are acid dissoluble tin ore. There is a very immate association relationship between cassiterite and other minerals. Little single particles of cassiterite can be seen through microscope, except that it inlays, packs and semi-packs in other minerals as limonite, hemanite and gangues in various form, including granule, fine grain and micro-fine grain, at a size range from 0.010mm to 0.002mm through rough measurement.It can be seen from preconcentration tests that it is inadvisable to recovery cassiterite by the process of discarding iron before recovering cassiterite. But it is better to eliminate iron from obtained tin concentrate. When using the flowsheet of discarding iron before recovering cassiterite, two kinds of iron concentrates are producted. The one from weak magnetic concentration contains 48.54% Fe at a yield of 0.15%. The other from intensive magnetic concentration contains 31.06% Fe at a yield of 1.17%. Both yields are very low and their iron contents are not in required standard. So it is economically unreasonable to fit magnetic separators to recovery iron minerals. The tests results of discarding tailings by spiral chute are also undesirable. Tin metal loss in tailings is at a high content even under different grinding fineness as 55%,65%,75% and 85% minus 200 mesh. When the grinding fineness is 55% minus 200 mesh, the tin loss in tailings is 25.58%. While at other three grinding finess the tin loss reaches 35% or more. And the loss increases as grinding fineness increases. So it is undesirable to discard tailings by spiral chute.The study on tin ore processing for the sample basises on gravity concentration to recover cassiterite by shaking table. Shaking table is an important and effective facility for tin recovery and tailing discarding. Through a lot of batch experiments, three different schemes are concluded to recovery the values from the run-of-mine. The first one is applying the first stage of shaking table to product rough tin concentrate at a primary grinding fineness of 95% minus 200 mesh. Then rough tin concentrate is delivered for further treatment as magnetic separation and hydrochloric acid leaching to remove magnetic mineral, hemanite and limonite, to give out final tin concentrate. Middlings from the first stage of shaking table is reground and reconcentrated to product rich tin concentrate. The second scheme is also using a primary grinding fineness of 95% minus 200 mesh for the first stage of shaking table to product part of tin concentrate and rich tin concentrate. Then middlings is reground and reseparated to give out another part of tin concentrate and rich tin concentrate. Two parts of concentrate and rich concentrate are respectively combined. The third one is that a primary grinding fineness of 85% minus 200 mesh is determined for the first stage of shaking table, to discard a large mass of tailings and product rough concentrate. Then rough concentrate is reground and reconcentrated to product tin concentrate and rich tin concentrate. Applying these three different process schemes to treat the tin ore, three kinds of middle grade tin concentrate is obtained, containing 39.01%,33.20% and 31.23% Sn, respectively, with a yield of 0.73%,0.84% and 0.91% at a recovery of 56.95%,57.33% and 58.90%, respectively. And the low grade rich tin concentrates contain 3.87%,3.46% and 4.46% Sn, respectively, with a yield of 1.08%,1.32% and 0.93% at a recovery of 8.36%,9.39% and 8.60%, respectively. Finally, the third scheme is regarded as the best process to treat the tin ore after beening compared and discussed with others. |
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