Yep, complicated set of variables involved and never enough information released to be sure exactly what is going on.
The previous announcement it looked like they were testing leaching process with significant amounts of acid, yet in this announcement they say "Low CaO suggests low acid consumption in REE leaching stage".... I checked my ITM data spready and can't see that CaO assays were ever released for the 'whole sample' results, only ever for the <45micron fraction. If we knew the whole sample was very high in CaO we would have predicted very high acid consumption, but that data was held back so we couldn't. CaO does look very low in the <45 (<0.1%), which should reduce acid consumption considerably (assuming it's not MgO +/- other elements reacting).
Is this implying that by beneficiating the high purity kaolin fraction, you achieve a higher grade REE and also a significantly better state to leach from? Sounds interesting, but well outside my area of expertise.... Using hydro-cyclones to cut only the <45 for leaching increases the TREO% by ~70% over the raw whole sample (same proportion of critical REO though). This is known as 'beneficiating' the ore into higher value plant feed. Added benefit is that cutting the <45 material was already a requirement to produce quality kaolin, dual upside. Downside is only ~45% of material from mine processed at plant so net loss of REO during high-grading process...
WC1 just acquired the Salazar REO-Kaolin project (SE WA near ESperance) which has had more year's work by ANSTO on recoveries and possible development paths than most. They have come to a similar conclusion; cut a <20 micron fraction, very acidic leach at moderate temperatures to recover 90% of REO and produce High Purity Alumina (HAP) as bi-product (or vica verca).
Difference at this stage with Caralue is that weaker acid (and maybe <45 instead of <20 cut) produces HP kaolin instead of HP Aluminium bi-product (HPA worth a lot more than HPK). Either way, I like the approach of multiple product revenue streams from a single project. Mineral sands have been doing it for years and it's a trean in a number of other projects I see these days.
The troubling flaw in the HPA, HPK plus REO projects is the small volume size. Even after multiple stage expansions, how big is the HPK and HPA markets, how much throughput can each project expect to get off-take for and fund?
An average HPA project will hope to sell 10,00tpa HPA from maybe 100,000tpa of raw kaolin ore feed. Assuming 33% recover after <20micron cut, @ 1000ppm TREO and 95% recovery delivers ~31t of REO's, worth say $75000/t in a basket 33% Critical REOs, or $2.5M revenue... basically an insignificant amount of REO product and revenue against the capex and opex and marketing involved (unless my maths is wrong).
Similar for HPK I suspect. Large volumes of kaolin feed, lower recoveries at less aggressive leaching, but in the end very little tonnes/revenue of REO product to be worth the effort. A decent kaolin mine that gets offtake for 500ktpa of 'all kaolin products' might only be able to market 25% of that as HPK (?). 150ktpa x 45% recovery to <45micron x 1000ppm TREO x 65% recovery of TREO (pH=1 acid leach) = 44tpa of contained REO in a mixed REO-carbonate. 25% of the 44t is valuable (Nd-Pr-Tb-Dy) for an average basket value of $75/kg or $75,000/t contained REO = $3.3M.
If my maths is wrong, please let me know. Otherwise, all these kaolin-REO plays to date look like just kaolin plays with some REO 'hundreds and thousands' sprinkled on top to make it look pretty...
