A new technique for the beneficiation of low grade carbonate-rich phosphate rocks by digestion with dilute acetic acid solutions: Pilot plant testing results

During beneficiation of phosphate rocks, huge amounts of oversize phosphate rocks are rejected from crushers. This reject mostly contains low tricalcium phosphate (TCP) content and high carbonate content. In this work, pilot scale experiments have been carried out to reduce the carbonate content by leaching the ground phosphate rock with dilute acetic acid solution in order to get marketable phosphate grades. Depending on the operating conditions of the leaching process, it has been possible to obtain a phosphate product (+53 μm) of 70-75% TCP content. The weight recovery of the phosphate product becomes higher if the mesh-number size cut is bigger than 53 μm, say 44 or 37 μm. By using this technique, more than 80% of the carbonates has been removed, and the tricalcium phosphate content has been increased to more than the 70% required in commercial phosphates. This depends, naturally, on the operating conditions of the leaching process as well as on the nature and size of the raw phosphate fed to the reactor. Possible routes for recovery of acetic acid from the acetate solutions produced during leaching, as well as proposals for production of fluorspar are presented.