STUDY ON MINERAL PROCESSING FOR A CASSITERITE ORE IN SOUTHWEST CHINA

摘要

In this article the beneficiation process of a cassiterite ore was investigated in order to provide a way for the utilisation of the cassiterite in Southwest China. The tin ore belongs to a skarn-type deposit containing cassiterite and stannite. The tin (Sn) accounts for only 0.70 per cent of the run of mine, in which 88.07 per cent of the cassiterite, 11.93 per cent of the stannite. And the dissemination size of the cassiterite is extremely fine, above 70 per cent of it is minus 0.02mm. Compositions of minerals in the ore are quite complex. The major metallic minerals include cassiterite, marmatite, magnetite, pyrrhotite, chalcopyrite, tetrahedrite, arsenopyrite etc. The major gangue minerals include talc, illite, quartz, feldspar, sericite, tremolite, fluorite, calcite, and kaolinite as well as a small amount of hornblende, montmorillonite, radite, etc. Due to its high relative density in relation to its gangue constituents, gravity separation has traditionally been recognised as a low cost and environmentally friendly process for treating cassiterite ore. But once its particles are of a size less than 43 μm, the efficiency of gravity separation will decrease markedly. Consequently, flotation technology was introduced to treat the materials of such a size fraction .The grinding size of this experiment is controlled at 75 per cent below 0.074 mm. The principle process flowsheet is first sulfide-removing by flotation to eliminate the effect of sulfide minerals on the subsequent separation, then the magnetic separation of magnetite. The tailings are classified into two size fractions, the coarse fraction is gravity separated to recover as much cassiterite as possible. Fine fraction is deslimed to ensure the total tin recovery, while for the flotation process of rough concentrate, gravity separation is used first followed by reconcentration. Thereby the total tin concentrate obtained contains 40.48 per cent tin with recovery 53.77 per cent.