|
Fluorspar or fluorite (CaF2) is one of the nonmetallic minerals which resembles the sulfide minerals in many ways. It occurs as dense, well defined crystals of definite chemical composition and therefore can be recovered in high-grade concentrates with good success.
If sulfide minerals are present in the fluorspar ore, generally it is advisable to remove them in a preliminary flotation stage with xanthate. Also, small amounts may be depressed with cyanide.
Fluorite is floatable with fatty-acid collectors such as oleic acid or tall oil. These collectors also float calcite, barite, and evens silicates if the latter are activated by the presence of alkaline earth metal ions. Depressants must therefore be employed in the circuit.
The standard procedure involves grinding the ore with soda ash, followed by flotation with sodium silicate, quebracho, and the collector. Quebracho calcite, but if used in excess it will also depress fluorite or at least cause excessively high collector consumption. Heat may also be considered a fluorite flotation agent; increasing the temperature of the ore pulp often results in reduced reagent consumption as well as a very marked improvement in concentration recovery and grade.
The most economic temperature depends on the particular ore. With some ores, optimum results are obtained at 40-50°C; other ores reportedly require heating to 100°C.
Fluorite-barite ores are probably the most difficult fluorite ores to treat. Separations can be made if there ore pulp is heated with the collector to 100°C before flotation. Quebracho has also been claimed as a barite depressant but is without effect on a number of such ores. In Dow laboratories, the best results have been obtained with a combination of heat (40 to 60°C) and lignin sulfonates.
|
