Ore sorters, concentrators and iron grade discussion, page-9

There are three primary designs being used in concentrating Lithium ore to lithium concentrate (DMS only, DMS+Flotation & Whole-of-ore flotation).

A DMS machine only produces two options - Floats and Sinks. The ore being processed isn't that clear-cut so they usually operate in pair's. The primary takes away all the light material as floats (at perhaps anything lighter than 2.75x as a density setting). This material goes through to a secondary smaller DMS that has a setting of perhaps 2.85x density. All the sinks at this density are the lithium concentrate. The higher the density setting the higher the grade produced, but the lower the recovery rate so there's a tradeoff. SC6 frequently isn't the best option for maximising returns.

The Middlings are this group are the rocks in the middle density hence the name. In this example they have a density of 2.75x to 2.85x. They will typically enough spodumene (or iron) to indicate further processing is worth wile, but not enough to get to the 2.85x density accepts. Consider a 2.8x density rock chip may be able to be crushed in half. It may become a 2.7x chip (waste) and a 2.9x chip (concentrate). It may even become a 2.5x waste chip and 3.1x near pure spod chip. The recrush will however rarely be exactly 50:50. Building a DMS circuit with Middlings enables further processing and higher recovery rates from that reprocessing.

The typical operational range for DMS plants processing spodumene is 0.5mm up to 10mm. All the crushing to get down to this size (and in recrushing middlings) creates fines of under 0.5mm. Under the DMS only processing option there is no recovery from fines, unless prices are high enough to DSO ship them. Finding information about the volume of crushing fines is difficult because many reporting systems don't mention them. Companies don't really want to shout out, we spent millions digging all this ore out of the ground. We then crushed it to a small size, and it got too small so we are chucking it into tailings. That is however basically what crushing fines are and they are they primary issue Core Lithium was experiencing around recoveries.

As an aside, one of the recognised DMS operational experts (Keith Muller) has noted that DMS tends to work best if a similar particle size is used in the DMS. The size range of 0.5mm to 10mm may involve two or three pair's of DMS concentration units. Even with multiple DMS units in the DMS only operation, recoveries are rarely above 70% and mid-60% is a realistic benchmark. It is however fairly common to see high 70% low 80% HLS recovery rates if these are purely the material processed in the HLS test which was first screened for fines.

With crushing fines being an issue, many operations have implemented or are looking at a smaller back end flotation plant. The DMS will process most of the ore (except fines). The fines and the last set of middlings will be recrushed down to the flotation size of ~0.1mm to 0.2mm with slimes (really small fines at ~25um or 0.025mm removed). The flotation plant will therefore add a layer of recoveries over and above DMS only but because perhaps only 20-40% of the material mined goes through the flotation plant they don't increase the capital cost as much as whole-of-ore flotation. As a start-up this option is less risky because the DMS can be generating cash flow while the flotation plant is fully commissioned, which can take many quarters.

Whole-of-ore flotation is the LTR (KV), Mt Holland and PLS P2000 expansion option. All the ore gets crushed down to ~0.1 to 0.2mm and put through a flotation circuit. The fines issue is removed but at a higher capital cost. There's more operational costs but higher recovery rates of nearer 80% or perhaps even above 80% are achievable.

Current comments indicate TG6 is thinking about a DMS plus back-end flotation plant which is likely to be a good solution.