Q&A with Brent Hilscher, Principal Process Engineer
We spoke about ore sorting early in 2018. What has changed since then?
I think the biggest change has been in the acceptance of the technology. It’s certainly gone mainstream. I’ve had people who said the technology wouldn’t work back in 2017 hire me for projects this year.
Have there been any breakthroughs in terms of technology?
There has certainly been some substantial incremental improvements with most of the technologies. Sensors are getting faster and more sensitive. We are learning to push the limits of what is possible. Bulk sorting technology in particular has been advancing particularly fast.
Can you explain the difference between bulk and particle sorting and explain what has been happening to advance bulk sorting?
Sure. Particle sorting looks at rocks in the ½ to 4 inch range and decides based on a scan whether each individual rock is worth keeping. Each machine can generally do between 100 and 200 tonnes per hour and the fact that each rock is looked at individually gives us an exceptionally sharp separation between ore and waste. Very good recovery, but also excellent waste rejection.
Bulk sorting can be shovel or conveyor based and it looks at large groups of rocks together. The packet size is typically in the 50-300 tone range. Meaning that a sorting system can tell us if a truck is full of ore or waste, but it can’t remove the ore particles from a truck full of waste.
Bulk sorting had been lagging behind particle sorting in terms of commercial installations but that is quickly changing. Most of the projects are secret, but I can say there are several Canadian and American mines testing various bulk sorting technologies at full scale. Bulk sorting has a huge advantage in high tonnage mines due to it’s negligible operating costs, and it’s ability to bump up the grade of marginal ore.
What sort of upgrade ratios are we looking at?
It depends on the geology of the particular site, but for a bulk sorting situation 10-20% grade uplift is a reasonable guess. For particle sorting 40-60% is reasonable and in some situations grade can more than triple
How often have you seen grade triple?
About 20% of the time on the projects I’ve done.
Can you tell before you start a project how successful it will be?
Usually yes. There are always surprises which is why we need to do the testing, but I have a checklist that is usually a good indicator of success.
Do many projects fail?
About 5% end up with a negative ROI and another 10 or 15% fail to meet company financial requirements for capital expenses. Over half of projects have payback periods under 12 months.
If I was an operator how would I know if I should be looking at sorting?
If you have an underground deposit you should have at least done a study by now. Your odds of getting a project with a 6 month payback are good.
If you have an open pit you need to choose between particle and bulk sorting and it’s not always a simple decision.
When do you make the choice between particle and bulk sorting?
If budget allows, it is usually worth testing both. If you can only afford to test one then you need to look at things like mine and mill costs, ore value, heterogeneity at different scales, and total tonnage.
As a trend low grade high tonnage deposits prefer bulk sorting and underground benefits from particle sorting
What will be the breakthrough in the coming year?
Faster bulk diversion systems that can take advantage of faster sensor times is coming.
A couple of the vendors are secretly working on step changes in sorter capacity which is always very welcome.
Other than that we will probably see some further improvements in XRF and XRT sensor technology.
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