The beneficiation of ultrafine phosphate

This paper discusses a novel method of beneficiation of ultrafine phosphate which allows the recovery of phosphate particles that are less than 20 μm in size and have long been considered in the industry to be unrecoverable. It has been standard practice over many years in the phosphate industry to separate and discard the ultrafine particles, due to unacceptable processing difficulties such as excessively high viscosity and/or poor flotation recovery. In contrast with the established methods of beneficiation of phosphate where classification by hydrocyclone is mainly used to remove ultrafines as tailings, the method described in this paper allows a high proportion of ultrafines to be recovered via flotation without prior separation.A number of variables and their effect on the flotation recovery of ultrafine phosphate are investigated including the pulp density and water quality during conditioning and flotation, type of flotation machine and reagents used to depress Fe2O3 and Al2O3. Some excellent results were achieved using samples containing up to 75 wt% −20 μm particles, including for example 91.2% P2O5 recovery to a concentrate grade of 34.7% P2O5 from a low feed grade of 6.46% P2O5 and 92.4% P2O5 recovery to a concentrate grade of 30.2% P2O5 from 10.6% P2O5 feed. Guar gum was found to be the most effective depressant for Fe2O3, whilst the Al2O3 was determined to be hydrophilic, resulting in low amounts being recovered to the concentrate, regardless of whether a depressant was used or not. The results of this work led to the development of the method described herein which is designed to recover phosphate from ores containing particles up to 80 wt% passing 20 μm, by flotation using a Jameson cell.

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► A process which successfully beneficiates ultrafine phosphate ore.
► The process can treat feed with up to 80 wt% −20 μm particles.
► Conditioning at high wt% solids and flotation with Jameson cells.
► Use of de-ionised water in conditioning reduces silica activation.
► The process recovers at least 80% P2O5 to a concentrate grade of 32% or greater P2O5.