AVZ Minerals Ltd (ASX:AVZ) has achieved solid recovery rates during phase two of metallurgical test work for the Manono Lithium and Tin project in the Democratic Republic of Congo.
The phase two testing delivered excellent lithia recovery results and supports the company 's selected definitive feasibility study (DFS) flowsheet.
First optimisation test results indicate 55.7% lithium oxide (lithia or Li2O) recovery into a concentrate grading 6.3% Li2O.
This work is ongoing and forms part of a DFS for the project.
AVZ managing director Nigel Ferguson said: “The progress of the phase two metallurgical program is delivering exceptional results in terms of lithia recovery and supporting the selected DFS flowsheet.
“Our DFS remains on target for release in the first quarter this year, enabling the advancement of the Manono project into production as quickly as possible on the back of securing the necessary financing.”
“Scalable to a full-size operation”
High pressure grinding rolls were used to replicate typical performance of industrial-sized equipment and generated around 13% more fines by mass compared to a typical control crush process – which translated to additional lithia losses to fines of circa 9%.
Ferguson said: “Despite a significant disparity in fines losses associated with the crushing method used, the first of the optimisation tests returned an excellent result of 55.7% lithium oxide recovery to a concentrate grading of 6.3%.
“This is an excellent result for the Manono project because our phase two optimisation work is essentially ensuring that our laboratory test work is scalable to a full-size operation.”
“Greater recovery improvements”
Ferguson said: “We continue our dense media separation (DMS) optimisation work and ongoing trials are expected to yield greater recovery improvements.”
Sub-samples have been screened at 0.3 millimetres and 0.5 millimetres to explore the recovery benefit of operating DMS cyclone unit with the finer feed down to 0.3 millimetres.
Coarse lithia concentrate generated from the processes will be subjected to further high SG recovery devices for the recovery of high specific gravity, liberated cassiterite (tin bearing) minerals.
The fines fraction will be de-slimed and concentrated using conventional tabling techniques to assess liberation and recoverability of cassiterite.
AVZ also tested ore variability yields for a given head grade, with the aim to supply both throughput design bandwidths and metallurgical inputs for pit optimisation and mine design.
These results indicated that recoveries ranged from 50.8% to 75.6% yielding concentrates ranging from 5.8% to 7.1%.
The general trend was that higher head grades equated to higher recoveries.
Balancing optimisation and economics
The company also conducted comparative dense medium cyclone (DMC) tests to explore the option to reduce DMC feed size from 0.5mm to 0.3mm.
The results indicated over 7% additional lithium oxide from the DMC circuit resulting from the reduction in screen size.
While the DMC efficiency fell away slightly with decreasing particle size, a further 5% lithium oxide overall recovery can be attained for similar product grades circa 6.1% - representing a significant increase in overall recovery.
An economic assessment, balancing the recovery benefit against operating cost and operability for this process improvement option will be undertaken post-DFS.