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Beneficiation of refractory rock phosphate by calcination and flotation

Minerals & Metallurgical Processing , 2011, Vol. 28, No. 4, pp. 187-192

Khoshjavan, S.; Rezai, B.


Separation of refractory rock phosphate (P2O5 = 11.5%) from the Dalir area, Iran, containing quartz, calcite and other impurities, by calcination and flotation processes has been successfully used to upgrade the phosphate values. Petrographic studies of this ore showed that collophanite was the major phosphate mineral and the main gangue minerals were calcite, dolomite and quartz. The results of characterization studies showed that the liberation degree of apatite occurred below the average grain size of 140 μm. Preliminary flotation tests were used to process the phosphate samples. Results of preliminary flotation tests showed that they don’t contain any desirable efficiency (grade or recovery) of P2O5. Calcination was the best process for preconcentration of this ore. In the desliming stage, about 14.4% of total P2O5 was removed. Encouraging concentrate grades were obtained after flotation with anionic and cationic flotation, successively. The reagent schemes that have been used in this study consisted of COCO-amine acetate and fatty acid as silicate and apatite collectors, respectively, as well as fuel oil and anionic poly acryl amid as promoter collectors. The optimum pH values for direct and reverse flotations of phosphate were 11 and 6, respectively. Experiments conducted using d80=140 µm deslimed fractions has yielded an acceptable grade of more than 30% P2O5 with a recovery of more than 62%. Finally, a laboratory flowsheet for the processing of Dalir refractory phosphate ore has been proposed.