How to profit from new mine-to-mill capabilities

By Walter Valery |

Challenging, tighter market conditions are driving the mining industry to improve productivity and reduce costs. We need to think differently.

We need smarter, more selective methods that are customized to individual operations. Every stage of the process—mining, comminution, separation—needs to be looked at, optimized for different ore types, and evaluated within the context of the entire operation. It’s a holistic approach, and a successful one. Companies all over the world, including one I’m very familiar with—the Antamina mine in Peru—have used it to drive throughput and efficiency to new heights.  

Start at the beginning 
Usually, blasting is the first stage in size reduction. But it should not be seen as just a way to make rocks small enough to load onto a truck. Done right, it’s the cheapest, most energy-efficient rock-breaking stage. The size of the blasted material has a big impact on the entire process, especially the amount of energy needed for downstream crushing and grinding. So getting it right in the blast is crucial for maximizing production and cost efficiency.  

Understand what you have to work with
The breakage from blasting is a function of the in-situ rock properties—the inherent strength and structure of the material. It changes across the deposit. If we understand the variations, we can adjust the blast energy for the conditions. Harder, less naturally jointed areas need more blasting energy, and softer, more fragmented areas need less. The result is a set of optimized blasting guidelines to provide the right amount of blasting energy (no more or less than required) for each ore type. This generates consistently broken material of an appropriate size for the downstream processes to optimize the overall performance of the operation and to keep things running smoothly.  

Carry the benefits through
Crushing and grinding are energy-intensive operations. They’re expensive. Optimizing them, given the upstream properties and downstream constraints, is the next step to increasing production and cutting costs.  

Just as the size of blasted material affects crushing and grinding, the particle size that grinding produces strongly affects recovery in the separation processes. So, it is important to understand the trade-off between producing a finer grind size (at higher cost and energy consumption and possibly lower throughput) versus the improved liberation and recovery that this generates. In other words, in each step, both the previous and following stages need to be considered to ensure the best overall result.

Delve into the data
We need to thoroughly understand both the ore and the processes involved in treating it if we’re going to improve the performance of the overall operation. This requires intensive data collection —ore characterization data, historical operating data, comprehensive audits, surveys, sampling campaigns data and benchmarking data.  Site-specific mathematical models are developed of each process—blasting, comminution, separation. With these, we can simulate a range of operating strategies for different types of ores in the mine and plant. Add in the right mix of people with the skills and experience to recognize problems, bottlenecks, and opportunities for improvement, and we have a cocktail for creating strategies that can improve the entire mine-to-mill operation. 

Consider the life-of-mine
Furthermore, when combined with the mine plan these models enable production forecast for the life-of-mine. These can be extended to develop geometallurgical models, to provide an understanding of ore variability and its effect on the mining and processing.  Long-term strategic planning becomes easier and more accurate to maximize profitability.

Sustain the benefits
It’s all in the plan. Strategies that have merit are based on mine and plant constraints and a cost/benefit analysis. To ensure the expected results are achieved, key performance indicators are measured, and the plan is tweaked to achieve the desired outcomes for the operation. Process changes are factored into managerial decisions and site-operating procedures to keep the benefits coming over the long term, and training ensures everyone understands and is on-board. This approach has helped operations significantly increase their metal production with no or very little capital expenditure. Costs are cut, energy is saved, and overall process efficiency improves (from the mine to the plant).

What about new projects or expansions?
This approach is equally valid and important when looking at new operations and/or expansions. Considering an expansion? This approach will identify the bottlenecks and determine an optimized solution for the particular operation and desired targets.  

For greenfield projects, this is the chance to start with a blank slate. Typically, mine and comminution circuits are designed largely independently. Circuits are often designed with an assumed run-of-mine size distribution. They don’t consider blast fragmentation models that look at actual, measured rock properties and a well-engineered blast design. So why are we surprized when the operation doesn’t meet specifications once it’s commissioned?  

Using blast-fragmentation and comminution models in the early stages reduces uncertainties and enables well-designed, cost-effective blasting, comminution, and separation stages. Rather than sticking to the same old—and often suboptimal—practices and circuits, we can develop something smarter that considers the specifics of the ore and the operation, and design something better, more efficient, and more profitable.  

A more efficient future
Metal prices are low and new ore deposits have lower grades and are complex and difficult to exploit. We are also facing growing challenges associated with the cost and supply of energy, water, and more stringent legislation. So, we need to think about improving resource efficiency.  How to do more with less—that is, maximizing value of the mines with less impact. This focuses on economic savings (ore resource efficiency) as well as environmental and sustainability benefits (eco-efficiency).  

Thus, we consider alternative processes and practices.  But every ore body and mining operation is different, so we need to tailor the solutions to suit. Perhaps high-intensity and selective blast designs to improve blast fragmentation and decrease energy consumption and increase throughput in downstream comminution circuits. In-pit crushing and conveying may offer a more cost- and energy-efficient method of removing material from the pit. Preconcentration may be implemented (in-pit or in-plant) to remove barren material prior to energy-intensive processing. Alternative and more efficient comminution technologies such as HPGR, VRM and stirred mills may be applied in novel flowsheet arrangements together with higher efficiency classification (such as fine screens alone or in combination with hydrocyclones). Or perhaps coarser grind sizes may be targeted for the first stages of separation to reduce the amount of material requiring fine grinding. Filtration and dry stacking of tailings could reduce water losses, reduce tailings footprint and eliminate the risk of tailings dam failure. 

Forward-thinking mining companies are considering and implementing these alternatives.  Hatch can help make them work for you too, bringing whole new levels of productivity—and profits—to your operations.