According to the characteristics of the disseminated ore, the concentration of scheelite can be combined with gravity separation and flotation or single flotation method. Some scheelite concentrator also carried out preconcentration. Because of the fragility of scheelite and the advantages of the flotation method, at present, the flotation is the most commonly used separation method for scheelite.
Scheelite deposit is often accompanied by a variety of sulfide ore, among which molybdenite is particularly common. In the process of dressing, generally the first floating sulfide ore, then floating scheelite ore. Scheelite flotation is carried out in alkaline medium, with sodium carbonate, sodium hydroxide adjusted pulp PH 9-10.5, commonly used inhibitors are sodium silicate (modulus of 2.2-3), white finch bark juice, tannin and various phosphates. The commonly used collectors are oleic acid, sodium oleate, tar oil, oxidized paraffin soap, etc. These collectors have foaming properties, generally do not add foaming agent.
Scheelite has good floatability, and the flotation process is complicated by the existence of similar calcium-bearing gangue minerals, such as calcite, fluorite and apatite. In order to improve the selectivity of flotation process, adding polyvalent metal salts (such as ferrous sulfate) to sodium silicate can significantly improve the flotation effect of scheelite.
Raising pulp temperature is also an important measure to improve scheelite flotation. The Peter Lov method USES pulp heating to 70-90 ° C, adding a large amount of water glass, so that the collector on the calcite surface is desorbed, and scheelite selectively rises.
"Lime method" flotation, can in the scheelite has excellent selectivity in the presence of fluorite, contrary to the usual theory, add the right amount of lime in the process of flotation is beneficial, think that adding lime in the flotation system, its calcium ions adsorption on fluorite, calcite and quartz surface, subsequently caused changes in surface charge, from negative to positive, and scheelite remain negative charge. When sodium carbonate is added and stirred with pulp, calcium carbonate precipitation is produced on the surface of quartz, fluorite and calcite, while scheelite is still negatively charged and has no precipitation on the surface.
Shear flocculation flotation is a promising method to improve fine scheelite flotation. The method is to add an appropriate amount of flotation agent in the mixing bucket before scheelite flotation, control the pulp pH and concentration, in the strong stirring hydrophobic ore particles collide with each other, thin water film, make the formation of hundreds of particles of scheelite flocculation, increase the effective size of fine particles, more easily adhere to bubbles quickly floating. A recent semi-industrial test in Australia showed that the recovery rate was about 74% with the conventional flotation method when the raw ore grade of 0.83% WO3 was ground to (40%-70%) -15 μ m. When the pulp was pre-treated with shear flocculation and re-flotation, the recovery rate was increased to 83%, and the coarse concentrate grade was also increased from 5% WO3 to 6% WO3.
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