Commerce Resources has completed the flotation pilot plant, the first phase in a series of flowsheet pilot plant tests on material from its 100% owned Ashram rare earth deposit. The primary objective of the pilot plant was to produce sufficient bulk quantities of flotation concentrate for downstream processing through to production of several kilograms of mixed rare earth concentrate, with a secondary objective of demonstrating flotation performance at the pilot level on a continuous basis. The company reports both of these objectives were achieved.
Approximately 4.3 t of Ashram bulk sample material, collected in 2012, was processed through a 6” flotation column on a continuous basis to produce about 1.4 t of flotation concentrate for downstream processing. The pilot plant was operated at Hazen Research, in Colorado, USA, in collaboration with Eriez Flotation Division, based in Pennsylvania.
Company President Chris Grove states, “The completion of the flotation pilot plant for the Ashram deposit is a significant milestone for the project. We now look forward to the downstream piloting that will begin shortly, as well as to the production of several kilograms of mixed rare earth concentrate.”
The pilot plant was comprised of three main circuits: grinding, reagent conditioning, and flotation.
The flowsheet used a simple grinding circuit comprised of a primary and secondary ball mill. No desliming stage was required to achieve the target grind specifications. The circuit also produced on-spec grind material using several different blends of feed, and operated continuously for up to 10 hours at a time.
As the primary objective was to produce flotation concentrate, the flotation pilot used batch conditioned grind material.
The 6” column flotation pilot plant operations were divided into two phases: a development phase where parameters were modified to accommodate the fact that the plant was operating at pilot scale, and a production phase where the flotation column ran continuously for extended periods of time (up to 13.3 hours per run for a total operating time of 98.7 hours) using the conditions determined during the development phase.
In total, some 1.4 t of flotation concentrate was produced from the conditioned grind material (mass pull of approximately 33%) over the entire 6” column flotation pilot program; development plus production phases. ICP-MS analysis of all the samples is pending. However, samples collected regularly during daily operations, and analyzed by Fusion XRF for Ce, La, and Y, indicate favourable total rare earth oxide (TREO) recoveries generally varying between 70% and +80% .
The pilot plant therefore achieved both its primary and secondary objectives through successful production of bulk flotation concentrate, as well as demonstrated continuous pilot operation for extended periods of time, with good flotation performance observed.
Currently, a continuous conditioning circuit is being built and will be tested with column flotation in the coming months. Additional work will include bench optimisation tests with reduced reagent dosages and will potentially be incorporated into a short 3” column flotation pilot run with continuous conditioning. The flotation concentrate will be dried, blended, and characterised for downstream processing through the HCl pre-leach and WHIMS flowsheet stages.
