Something of note here is that we’re going to have, and this is empirically determined – Dr. Andre Laplante, 2005 – for every 10% of gravity recovery in a flotation plant, generally you will improve overall plant recovery by 0.5% to 5% depending on the mineralogy, the operation of the plant, a variety of different factors. So that’s certainly nothing to turn up your nose at, people will spend years trying to get several more percent of global plant recovery, but that’s only one side of the story here.
One of the benefits, economically, is the overall recovery, and that’s fairly straightforward, but in a flotation plant, there are a few other considerations here. So one thing to note is this statement here: not all of the gold recovered would have been lost to final tails. This is the difference between this number here.
You’re going to have 10% gravity recovery, but maybe only 0.5% to 5% of additional overall recovery. So what’s the point of putting more gold into the gravity concentrate? And is there a point? A lot of flotation plants are going to be gold plus something else – or more accurately, something else and then gold along with it. So in a gold-copper situation, there may not be as strong of a benefit as, let’s say, polymetallic; you’re selling a copper concentrate. You’re going to get paid really well for the gold.
Maybe not as much of an economic incentive, but in a polymetallic concentrate, if it’s going in a zinc concentrate or a lead concentrate, silver – but let’s say lead or zinc. You may not get paid at all for that gold. Some products such as zinc concentrate may pay as little as zero for gold.
Whereas copper concentrates can pay well over 90%. So there’s an economic benefit here, especially in polymetallic operations, to reallocate or relocate the gold in a different concentrate that can be sold in a different way to get the value out of it. So perhaps there’s a bit of a bump in overall recovery, which is great, but it doesn’t necessarily do you any good if you’re not getting paid for that additional gold. So having the gravity concentrate will allow you to sell it in a different way, be paid better for it most likely, and also be paid more quickly.
There’s also a knock-on benefit here: payment for gold in a float con can take weeks or months, depending on smelter contracts and distance and whatever. But generally, payment for gold as a gravity concentrate is much faster: you can send it to a refiner and get paid very quickly for that gold. So there’s also a positive cashflow implication when you put it in a gravity concentrate.
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