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Recent articles in the press and company announcements might create the impression that the group of mining companies that are commissioning spodumene beneficiation plants at present will produce spodumene concentrate that is interchangeable with Talison SC6.0 chemical grade concentrate.
At present the Talison Greenbushes' mine in Western Australia supplies almost all of the world’s current production of chemical grade spodumene concentrate. The ore body is not only large but also has superior grade to the new producers coming on line.
[Spodumene concentrate- Run-of-mine (ROM) ore is treated in a minerals processing plant to remove waste, non-lithium containing minerals, to produce an ore with higher lithium content (beneficiated)].
The chemical formula for the spodumene mineral is Li2O.Al2O3(SiO2)4 and in its pure form would have a lithium content (usually expressed as Li2O) of 8.03% Li2O. No concentrate has a lithium content as high as 8.03% and the lower the lithium content of the spodumene concentrate, the higher the amount of other mineral impurities in the concentrate.
So what does this mean to the downstream lithium chemical converters who have historically processed Talison SC6.0 spodumene concentrate?
Grade
While Talison supplies SC6.0 to the market, and has done so for 24 years, new producers might struggle to achieve a grade as high as Talison’s 6% Li2O . The consequence of a lower grade is that more concentrate is required to produce the same amount of lithium carbonate. Since the Chinese converter plants are limited in calciner capacity, these plants will produce less lithium carbonate, or other lithium chemicals, as a result of a lower grade spodumene concentrate.
[The calciner is usually the first unit operation in which the α-spodumene is converted into β-spodumene by heating the concentrate to around 1,000°C to make the lithium in the spodumene amenable to reaction with acid].
Impurities
The Talison concentrate contains predominantly spodumene and quartz with low amounts of other impurities.
The presence of other minerals in the concentrates can have two main impacts on the Chinese converters. The first effect is that greater amounts of impurities will be extracted with the lithium and make it more difficult for them to produce battery grade lithium carbonate.
The second potential impact is that the other minerals include iron containing minerals, feldspar, phosphate minerals and micas. It has been noted that elements such as iron, phosphorous, potassium and calcium can melt at low temperature or form eutectic mixtures with other minerals which then melt in the calciner. The molten minerals form clinker (lumps). These clinker lumps can become a headache for converters in the operation of their plant as well as lowering the amount of lithium that can be extracted in the subsequent leach.
In general, a converter would remove the clinker lumps and crush them in order to recover as much of the lithium as possible. However, as a general guide, the lithium recovery from clinker is unlikely to exceed 75% when compared with calcine without clinker formation.
A critical difference is the iron content. The iron content of a Talison spodumene concentrate is lower than the other concentrates which are expected to have iron contents in the range of 1.5% - 1.9%.
In addition to the operating problems mentioned previously, the Chinese converters are also likely to have a lower lithium recovery from the new spodumene concentrates.
Particle Size Distribution of the Concentrate
The beneficiation of the mined ore to produce spodumene concentrate differs from plant to plant. In the case of the RB Energy plant, which is currently mothballed, the concentrate was produced by flotation and has particle size of less than 74 microns (0.074 mm).
In contrast the original concentrate from Galaxy’s Mt Catlin operation was produced using HMS (heavy media separation) and would have had a large particle size probably closer to 3mm.
Talison produces the concentrate by a combination of HMS and flotation and the concentrate would have a wide size distribution from 3mm down to less than 75 microns.
What is the impact on the Chinese converters?
There are two likely impacts namely dust handling and time to heat the concentrate in the calciner.
If the calciner is not designed for a dusty feed, then the amount of dust that is blown out (elutriated) from the calciner will be significant. It is reported that one Chinese converter that changed to supplier of concentrate, experienced 30% of the feed being blown out of the calciner. If the amount of dust blown out of the calciner is large, it will have a detrimental effect on the capacity of the calciner.
The second impact is time to heat up the calcine. The larger the particle size, the longer it takes to heat up to the conversion temperature. Conversely, small particles heat up much faster. If the calciner has been designed for larger particles, then dust may be a problem. Conversely, if the calciner was designed for smaller particles the capacity may be considerably reduced in order to heat the particles to the required temperature.
Summary
Introduction of new spodumene concentrates into existing lithium converter plants treating Talison SC6.0 is likely to impact the capacity of these plants and/or result in significant operational issues.
Grant Harman
Principal at Lithium Consultants
