More value, less impact

By Kristy-Ann Duffy | December 11, 2018

In mining today, high-grade deposits are all but gone. So, we’re left trying to develop poorer deposits with more complex mineralogies that are harder to access. How do we do this in an economic and environmentally sustainable way?

The secret to success is understanding the entire process (mining, comminution, and processing) and how the stages interact. Then, it’s a matter of tailoring the solution for the particular deposit and operation. One thing is clear. There is no one single solution that can be copied and pasted into any operation. Each has its own ore bodies and types, locations, environmental factors, and so on.

To maximize value, we need to consider the entire operation—the mine and processing plant together—rather than optimizing each in isolation.

If it’s done right, and tailored to the different ore types being mined, blasting can be the cheapest and most energy-efficient rock-breaking stage. The size of the blasted material affects the throughput, energy consumption, and costs in downstream crushing and grinding operations, so it’s a critical first step.

Likewise, the final grind size and liberation strongly affects separation. A finer grind size is likely to improve recovery, but this needs to be weighed against the additional cost and energy consumption required to achieve the finer size. This varies considerably according to ore characteristics (particularly liberation and hardness) and breakage mechanisms, so the trade-offs need to be understood in each case.

Across the industry, these considerations are well understood, but solutions are often not well implemented. Some assume that simply increasing the explosives in blasting will optimize the entire value chain. But for holistic mine-to-plant optimization, blast intensity is not indiscriminately increased. Rather, it is adjusted to better suit the different types of ores, the comminution equipment and circuit arrangement, and the separation process.

Holistic optimization requires a detailed understanding of the ore types, geometallurgy and all the processes, mine-to-plant. So careful observation and discussion with site personnel, data collection, analysis, modeling, and simulation are combined with extensive industrial experience to identify solutions tailored to each operation, their people, and culture.

Many of the strategies for improving the efficiency and sustainability of mining operations are not new, but they do involve new ways of applying existing technologies and tailoring solutions to the process and the ore. Resource, energy, and water efficiencies are improved by selective mining that is followed by processing only what needs to be processed.

Comminution is usually the single largest consumer of energy at a mine site. Preconcentration (by prescreening, bulk and/or particle ore-sorting, or gravity concentration) can reduce the amount of material needing comminution and further downstream processing. That saves cost, energy, and water.

The energy that comminution needs increases exponentially as particle size decreases. So, it makes sense to only grind as finely as necessary for effective separation. Targeting coarser grind sizes for the first stages of separation can significantly reduce energy consumption. It can be more effective to use the first stage to liberate and reject barren material, which is often released at coarser sizes than the valuable mineral. Then, there is a smaller volume needing grinding and final separation to liberate the valuable material.

Effective solutions cross boundaries between geology, miningprocessing, and engineering. We’re always ready to assemble the best cross-sectional team of specialists to develop novel solutions that are tailored to the project and able to deliver the best strategies overall. This allows us to contribute to advancing technologies and practices to drive positive change in the industry, and especially for our clients.

Read more from Kristy-Ann Duffy on how to achieve a small footprint mine here.