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Removal of Dolomite from Phosphate Pebble Concentrate by Enhanced Jigging



Dolomite [CaMg(CO32] is an objectionable impurity in phosphate ores due to its MgO content. Separating dolomite from phosphate ores (apatite) has proven to be difficult due to very similar mineralogical properties. It is desired that a process reduce MgO content in the concentrate to less than 1%, while still achieving respectable phosphate recoveries.

Jigging was investigated as a low-cost physical separation method for the removal of dolomite from high-MgO phosphate ores. It was determined by liberation analysis that the dolomite is sufficiently liberated from phosphate, making it theoretically possible to remove a significant amount of MgO without crushing or grinding. A laboratory-scale jig was designed and built to examine the feasibility of jigging as a process for separating dolomite from phosphate pebble. Using a batch jigging procedure, it was determined that the optimal pulsation frequency was 200 pulsations/minute.

A continuous jigging laboratory-scale testing procedure was developed and alumina balls were used as ragging material. Jigging tests were completed using different phosphate ores with water as the jigging fluid. Use of a dense jigging fluid (CaCl2 solution) was explored as a possible method for increasing separation efficiency. It was found that using a dense fluid resulted in an increase in dense particle recovery rate, corresponding to approximately a 52.3% increase in throughput over experiments run with water.

Contact angle experiments were conducted to determine whether existing froth flotation reagents could make dolomite sufficiently hydrophobic for a novel “flotation jigging” process. It was found that the available reagents could not provide sufficient hydrophobicity to reliably separate dolomite from phosphate. These experiments also indicated that conventional froth flotation would not be expected to provide adequate dolomite removal using these reagents.

Cost estimation calculations are included that indicate that a jig process is approximately 1/20th the cost of a comparable-capacity heavy-media process for removing dolomite. It was also calculated that a jig process would be cheaper than a froth flotation process, even if a suitable dolomite flotation reagent becomes available that is useful for conventional flotation.