Flotation process for upgrading cassiterite concentrates

摘要

Cassiterite is obtained from tin ore by grinding the ore to liberate the cassiterite; subjecting the ground ore to a first flotation step with fatty acid as the flotation reagent to float a rougher or primary concentrate containing the cassiterite; drying the concentrate; heating the dried concentrate to a temperature above the boiling point of the fatty acid to remove at least most of the fatty acid from the particles of the concentrate; subjecting the resulting concentrate to a second flotation step with a cationic collector as the flotation reagent to float the gaugue minerals in the concentrate; and recovering the cassiterite as the underflow of the second flotation step. If necessary, before the first flotation step, the ground ore may be treated by flotation and/or magnetic concentration to remove metallic sulphides (using a xanthate or thiosulphate collector) and/or iron oxides. Desliming of the ground ore is carried out, e.g. in a hydroclassifier, before the first flotation step either before or after the sulphide flotation. The fatty acids that may be used are oleic, stearic, linoleic, and palmitic and mixtures thereof including tall oil. Optimum flotation is obtained in the p pH range of 4.0 to 6.5; the pH should not however exceed 8.5. A suitable cationic collector is an amine, e.g. dodecylamine hydrochloride. A gaugue dispersant, e.g. Na2 SiO3 may be added to the first flotation step and a depressant for the cassiterite such as a carbohydrate or carbohydrate derivative, e.g. sorghum flour, may be added during the second flotation step. The gaugue float from the second step may be refloated to drop out additional cassiterite which is then added to the underflow from the second step to increase the tin recovery. Also, the underflow may be refloated to remove additional gaugue minerals to increase the tin content of the final product.