SELECTIVE LEACHING AND ACID RECYCLE ON SONGWE HILL RARE EARTH CONCENTRATE

摘要

Mkango Resources Limited is developing the Songwe Hill rare earth project in south east Malawi. The project holds an Ni 43-101 compliant mineral resource estimate comprising of an Indicated resource of 13.2 million tonnes grading 1.62% total rare earth oxides (TREO) and an Inferred resource of 18.6 million tonnes grading 1.38% TREO. A mmeralogical program identified the fluorocarbonate mineral, synchysite, and the phosphate mineral, apatite, as the most prevalent rare earth host minerals whilst calcite and ankerite were Identified as the most common gangue minerals present. Extensive metallurgical testwork was conducted initially at Mintek in South Africa and more recently at Nagrom in Western Australia. A robust flowsheet has been developed consisting of comminution, flotation, hydrochloric acid leaching, purification, cerium rejection and rare earth precipitation delivering a product suitable as feed to a rare earth separation refinery. More recently the leach process has been enhanced to incorporate a two stage selective leach process as well as acid recycling via calcium sulphate precipitation. This approach offers innovative advantages including a significant reduction in acid costs as well as a further concentration of the rare earths providing a reduction in downstream capital and operating costs.