Abstract
Fluorite, CaF2, is considered a strategically important mineral as it is a raw material for many strategic industries. Froth flotation is reported to be the most efficient and economically viable process for the production of an acid-grade product with a CaF2 content of at least 97%. Selective flotation of fluorite from gangue minerals, e.g., calcite and barite, is challenging because these minerals have similar physicochemical properties. This study employed batch flotation tests coupled with mineralogical analysis to design suitable customised flowsheets and efficiently optimised reagent regimes for optimum production of acid-grade fluorite concentrate from two different fluorite ores by the froth flotation process. The effect of pulp temperature on fluorite flotation was investigated in this study with the objective of lowering pulp temperatures in fluorite flotation. The results showed that an acid-grade CaF2 concentrate could be obtained from the flotation of both ores at ambient pulp temperatures. This eliminates the requirement for high-temperature pulp treatment, which would result in a significant reduction in thermal energy costs. This study showed that an understanding of gangue mineralogy is key to process optimisation for acid-grade CaF2 production. Although an acid-grade CaF2 concentrate could be produced from both ores, the flowsheets and reagent regimes were markedly different. For instance, the production of an acid-grade CaF2 product from a high quartz and calcite ore was achieved by employing a simple rougher–multiple cleaner flotation circuit using tannin and sodium silicate as calcite and quartz depressants, respectively. On the other hand, the production of an acid-grade CaF2 product from the flotation of the pyritic ore required a pre-sulphide flotation stage for upfront sulphur removal and the use of a sulphide depressant. Multiple stages of cleaning were required for improved selectivity in the flotation of both ores.
Highlights
Fluorite, CaF2, is considered a strategically important mineral that is used in the production of hydrofluoric acid and as a flux agent in the steel making industry
This study investigated the role of gangue mineralogy on flowsheet and reagent regime selection on the processing of two different fluorite ores
Customised flowsheets and efficiently optimised reagent regimes were investigated for the optimum production of acid-grade fluorite for each ore by the froth flotation process
Summary
CaF2 , is considered a strategically important mineral that is used in the production of hydrofluoric acid and as a flux agent in the steel making industry. Froth flotation is reported to be the most efficient and economically viable process for the production of an acid-grade product with a CaF2 content of at least 97%. The mineralogical compositions of current fluorite deposits are becoming increasingly complex, making the selective flotation of fluorite from gangue even more challenging. Typical gangue minerals include calcite, quartz and barite [1]. Some sulphide gangue minerals, such as pyrite, galena and sphalerite, may be present in fluorite ores. Selective flotation of fluorite from the gangue e.g., calcite and barite, is challenging because all these minerals have similar physicochemical properties
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