Re: Mining a clay material
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Message: Mining a clay material
There seem to be the two uncertainties about the process, how you separate the liquids from the solids and whether the concentration of the lithium sulfate in the leachate is high enough for the process to be competitive with other downstream purification processes. The chemistry of the downstream process is not a large concern. It will likely be tailored to the chemistry of the leachate, but each step is standard on its own.
The details are a little sparce in the PFS, but pg 137 contains the following:
"After Ore Preparation, the ore will be transferred as a slurry to the Leaching circuit. Sulfuric acid will be mixed in with the slurry to liberate the lithium from the clay. The leaching process will take place in stirred reactors designed to (a) maximum lithium dissolution from the ore and (b) optimize sulfuric acid consumption. The lithium bearing solution, i.e. “lithium brine”, will be separated from the leach residue by filtration. The filtered residue will be washed to recover any remaining free lithium, and then conveyed to the clay tailings facility. The wash solution will be recycled to the slurry ore in the attrition scrubbers. Crushed limestone and residue from the neutralization filters (Section 17.1.3) will be added to the leach clay residue to produce a geotechnically stable clay tailings."
Elsewhere in the PFS:
"The properties of the claystone after leaching show acceptable settling and filtration rates. Washing of the spent clay showed very high lithium recoveries."
Not sure what "acceptable" means...
The article I posted on extracting lithium from clays may not be the most helpful. It appears to be from the late 1980's. It was written with regards to the McDermitt Caldera (Thacker Pass) and I hoped it might have some more details as to how to get the lithium sulfate leachate out of the clay. This article identified belt filtration which I believe may still be relevant technology. Maybe something like one of the following:
https://www.youtube.com/watch?v=eBbPIxkYfPI
https://www.youtube.com/watch?v=W2UIZqdkTyE
I am optimistic about the progress being made.
From the PFS pg 6:
"The current flowsheet does not include an allowance for traditional ore upgrading, and further investigation of ore upgrading is recommended at the next engineering phase, although it is not necessary to the viability of the project.
and from the recently released annual report:
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Process Engineering and Design Update
A process testing facility and laboratory has been commissioned in Reno, Nevada to optimize the process (predominantly to reduce the consumption of sulfuric acid), prepare tailings samples for stability and geochemical analyses, and to provide feed samples to crystallizer vendors who will design the equipment and are expected to provide performance guarantees. The results of the pilot plant test work will be used to finalize the design of the front-end of the process where lithium is extracted (dissolved) from the ore. To date, Lithium Nevada’s process testing facility has produced over 15,000 kg of high-quality lithium sulfate brine at the Thacker Pass Project. The process has been optimized by upgrading the ore through a wet attrition process followed by a hydrocyclone to remove coarse material with relatively low lithium content. The process test work has demonstrated an increase in lithium feed concentration, which results in reduced acid consumption per tonne of LCE. In addition to optimizing acid consumption, the process testing facility has also generated tailings samples that are being used for stability and geochemical analysis, as well as feed samples to crystallizer vendors who will design the equipment and provide performance guarantees.
AXP
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