Pure Energy Minerals Reports High Lithium Recoveries From Successful Mini-Pilot Testing Campaign
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December 13, 2016 07:32 ET | Source: Pure Energy Minerals Limited
VANCOUVER, British Columbia, Dec. 13, 2016 (GLOBE NEWSWIRE) -- Pure Energy Minerals Limited (TSX-V:PE) (FRANKFURT:A111EG) (OTCQB: PEMIF) (the “Company” or “Pure Energy”) is very pleased to announce the initial results from Pure Energy’s recently completed innovative mini-pilot test work. The mini-pilot campaign was successful on all counts and demonstrated efficient recovery of at least 85% of the lithium from the tested brine. The mini pilot trial also produced battery-grade lithium hydroxide monohydrate. The Company sees this milestone as an important proof-of-concept for modern, efficient and environmentally sustainable lithium brine processing techniques without the use of evaporation ponds. The newly developed flowsheet will be a foundation of Pure Energy’s forthcoming Preliminary Economic Assessment (PEA), and it will constitute a key building block for a larger scale continuous pilot plant. A summary of the main findings is shown below, and greater detail will be provided in the forthcoming PEA.
Summary of Testing Performed and Results
The testing work performed by Pure Energy and its technology providers Tenova Bateman Technologies (TBT) and SGS Canada evaluated a four-stage process:
Pre-Treatment ⟹removal of divalent ions including alkaline earth elements by membranes (LiP™) and chemical precipitation;
Solvent Extraction (LiSX™) ⟹ preferential extraction and concentration of lithium from the pre-treated brine to make a high purity lithium sulphate solution;
Electrolysis (LiEL™) ⟹ conversion of high-purity lithium sulphate solution into high purity lithium hydroxide solution; and,
Crystallization ⟹ evaporation, crystallization and centrifuge separation of battery-grade lithium hydroxide crystals.
Important Findings from Mini Pilot Plant Test
One of the most important work products of the mini pilot plant is a preliminary process flowsheet, a simplified version of which is shown below as Figure 1. The test work also supports several key performance indicators that warrant continued development and scale-up of the TBT Process for commercial scale lithium production at the Clayton Valley South Project (“CVS Project”):
Achieved overall lithium recovery of >85% from the tested brine;
Successfully removed the major interfering elements from the solvent extraction (SX) feed brine: calcium (Ca), magnesium (Mg), and strontium (Sr);
Achieved near 100% extraction of lithium by LiSX™;
Achieved high lithium concentration factors, approximately 38x, during the LiSX™ stage;
Crystallized battery-grade lithium hydroxide monohydrate with a high quality distribution of grain size and morphology; and
Identified several areas in the process that are ripe for improvement and optimization of costs and efficiencies in a future scaled-up operation.
To view Figure 1, please visit:
http://orders.newsfilecorp.com/files...48_figure1.jpg
Figure 1 – Schematic Summary of Preliminary Flowsheet for Treatment of CVS Lithium Brine
Patrick Highsmith, Pure Energy Minerals CEO commented, “The TBT and Pure Energy technical team has done some extraordinary work in this mini-pilot plant. Not only is this a proof-of-concept for the use of TBT’s new technology in lithium production, but the team collaborated and optimized the process on-the-fly. The flowsheet you see here is a significant improvement upon our projections from the bench scale tests, and we believe there is a great opportunity for economic application of this technology to commercial scale production. The preliminary estimates of lithium recovery by our process are at least a 70% improvement over the typical 50% recovery experienced by traditional evaporation. The current resource drilling that is underway at the CVS Project and the subsequent update to our mineral resource are the last precursor steps to our PEA. We look forward to more fully describing the project and its economics during Q1 of 2017.”
Pre-Treatment
The pre-treatment of the CVS brine to remove key interferents (particularly Ca and Mg) is a prerequisite if selective solvent extraction of lithium is to be used. The CVS lithium brine is an ideal candidate for the direct use of modern membrane technology as it has relatively low concentrations of Ca and Mg (compared to other brine deposits globally), and is not saturated with other solutes that may cause problems with membranes (e.g. gypsum). In order to test the use of membranes for pre-treating the brine ahead of solvent extraction, TBT tested a synthetic brine with the same composition as brine recovered during bulk sampling from exploration well CV-1 (from the CVS Project). They tested an array of commercially available membranes from several suppliers to determine whether the main interferents (Ca, Mg and Sr) could be effectively reduced to acceptable levels. The first part of the test work consisted of screening 8 different membranes in a flat-sheet configuration at an operating pressure of 60 bar, and evaluating how the various membranes transmitted lithium whilst rejecting alkaline earth elements. Following completion of the flat-sheet testing, TBT selected a single membrane based on its superior relative performance and proceeded with testing it in a spiral-wound module test rig, again at 60 bar.
The recently completed test work demonstrated that even in a relatively simple, ‘single-pass’ arrangement (i.e. brine being passed once through a single set of membranes), approximately 85-90% of the lithium is recovered, while at the same time, approximately 91% of Mg, 90% of Ca and >99% of Sr are rejected. These data are extremely encouraging and validate the use of modern membrane technology to pre-treat CVS brines. Additional test work is ongoing to further refine and optimize the use of membranes prior to continuous testing in a full pilot plant configuration, including evaluation of variable pressure across the membranes and the use of anti-scalants in the process. The next stages of work are being completed by TBT and their partner, GE Water & Process Technologies.
In a parallel phase of pre-treatment test work (performed by SGS Canada), the lab treated CVS brine (actual raw brine sample from CV-1) with additions of caustic soda (NaOH) and soda-ash (Na2CO3) to determine whether direct chemical precipitation could be used to remove divalent contaminants. This work successfully demonstrated that >99% of Ca, Mg and Sr could be removed through careful pH control with negligible loss of lithium through co-precipitation. Subsequent work was completed using a High Density Sludge (HDS) circuit that allowed semi-continuous operation over 3 ½ days to investigate whether the solids produced by the direct chemical precipitation could be aggregated and thickened (using a flocculant), and then removed from the brine flow. This phase of work also showed excellent results, and resulted in a steady-state process that produced brines with Ca levels reduced to 2 mg/L, and Mg and Sr both <1 mg/L, also confirming very low lithium losses. While it is unlikely that direct chemical precipitation would be used in isolation to remove divalent impurities from the CVS brine (owing to relatively high reagent costs), it is likely that some form of this unit operation will be used after the membrane step to polish the permeate and raise its pH to target levels prior to feeding the lithium solvent e
Pure Energy Minerals Reports High Lithium Recoveries From Successful Mini-Pilot Testing Campaign TSX Venture Exchange:PE
