Hi Thesi,
At 50% yield, 70kt of crushed ore would produce 7kt of spodumene concentrate . The conversion is 10:1, I'm not sure what the 50% actually represents. Perhaps there are two stages, 10:2, and 2:1.
Please refer to the 19 July announcement, specifically the table on page 2, which sets out the production summary forecast in a matrix of spodumene at 50% and 75% yield on the horizontal, and 800ktpa and 1.6Mtpa on the vertical.
Interestingly, the last paragraph on page 2 suggested an additional 30kt of crushed ore (total 100kt) was held on the ROM pad in July, which would convert to a total of 10kt of spod. With an additional 50kt of ore lying in situ (where it was crushed), that gets us to potentially 15kt of spod.
"Over the last 3 months, mining of the ore grade TSF material has been largely completed (50kt ore remains in situ) and is currently stockpiled ready for use as feedstock in the fines circuit. The ROM pad currently holds 100,000kt of blasted ore ready for crushing and feeding into the coarse circuit."
Here was something interesting I picked up from the Baillieu Holst report (they model 18kt spod in Dec16):
"Processing – ... The four stage crushing circuit has been reduced to three stage and rather than operating for 12 hours per day is now able to operate continuously following the installation of acoustic cladding and baffling around the crusher to reduce the noise levels emanating from the site.
"Mining – ... Feed for the plant will initially be broken ore – essentially just a rehandling exercise and much of the pre-strip for the first two years has been done.
On the mining excerpt, I read there is ample broken ore available, over and above the 50kt lying in situ, to feed the plant for the first two years. 'Essentially just a rehandling exercise'.
On the processing excerpt, not sure to what extent this has already been factored in but they can now run their crushing circuit 24 hours p/d (previously only 12 hours p/d).
To conclude, they would need an additional ~300,000t of crushed ore to meet the 45kt production target. I have no sense of how long it takes to put that quantity of ore through the commissioning process.
