In the 1990s metal prices were trending in a long-term decline and the usual cost-cutting exercises were adopted. Cuts to research and development made innovation difficult and the outlook was grim. But necessity is a strong motivator, and these conditions spurred the Mine to Mill movement that optimised across organisational ‘silos' and utilised new technology tools, innovative software and increased computing power.
Many applications of Mine to Mill exploited the fact that comminution is usually the site processing bottleneck and blasting is more efficient at breaking rock than grinding. This approach sought to:
- understand and characterise rock breakage from mining to the mill
- develop models and simulators for blast design, fragmentation, crusher and mill circuits
- develop tools to measure in real time the particle size distribution of rocks on run-of-mine (ROM) muck piles, at the primary crusher truck dump pocket and on conveyors
- ensure effective communication across the silos between geologists, blast design engineers, mining engineers and metallurgists.
These methods and the technology tools available in the 1990s were widely adopted at numerous sites around the world with significant benefits. Semi-autogenous grinding (SAG) mill throughput increases of 10–20 per cent were common. This was the advance the industry desperately needed. It was low capital cost; it was obvious. It was here to stay.
Except, in too many cases, it didn't. In the minerals price boom of the 2000s Mine to Mill was no longer necessary to ‘survive', even though it was still good business. Some operations, including some of the early success stories, slipped back to old habits of optimising within organisation silos instead of across them. Fortunately, other operators still embraced Mine to Mill and developed new techniques. Mine to Mill was still successful, but not as widely adopted as we had expected it to be.
Now the boom has ended and operations are again under cost pressure. Since these are the same circumstances that created Mine to Mill, it seems time to achieve the wider adoption.
Since the 1990s many new or advanced technology tools are now available for Mine to Mill projects: blasthole sensors, new explosives formulations, new blasting techniques and modelling, ore tracking devices, improved image analysis to determine size, texture and colour of coarse ore, grade sensors, whole-stream simulation tools, and even more powerful computing hardware and data analysis software.
If we could achieve so much in the 1990s, how much more can we achieve today when we have the same imperative, the same potential and a larger number of high technology tools?
Cameron, P, Drinkwater, D and Pease, J, 2016. The ABC of Mine to Mill and Metal Price Cycles, in Proceedings 13th AusIMM Mill Operators' Conference 2016, pp 349–358 (The Australasian Institute of Mining and Metallurgy: Melbourne).