Evolving to meet future challenges in mining and minerals processing

By Kristy-Ann Duffy | February 12, 2020

The last thirty years have seen a dynamic shift in mineral processing. The mining industry is facing lower ore grades and more complex deposits. Not to mention the growing challenges associated with the cost and supply of energy and water. The end-game is to develop smarter, more selective practices, tailored to suit each operation to improve efficiency, and reduce power and water consumption. We’re sitting down with Kristy-Ann Duffy, a process consultant for Hatch’s mining and mineral processing division, to look at some of the challenges we’ve overcome, but also those we’ll have to face in the future. Here’s our recent Q&A!

Thank you for joining us today, Kristy-Ann. We know the industry’s faced some major changes over the past few decades. What would you say are some of the key innovations or technologies that have been particularly game-changing?

Thank you for having me. I have seen significant improvements in efficiency and productivity achieved through mine-to-process (or mine-to-mill) optimization, which has consequently improved the profitability of numerous operations globally.

The objective is to maximize production with the available assets while minimizing the overall cost per ton treated, thus maximizing company profit in a sustainable manner. Mine-to-process involves looking at the complete operation, including the mine and processing plant, rather than optimizing each in isolation.

There’s also been greater application of efficient comminution technologies such as stirred mills and high-pressure grinding rolls (HPGR). However, it’s important to understand the overall impact, including ancillary equipment and ore characteristics, to determine the best solution in each case.

How have we been able to adapt to these changes and remain a leader in the industry over the last thirty years?

Hatch consulting specialists have been working in holistic mine-to-process optimization, improvement, and design for many years and have collated a wealth of experience and industrial operating data. From this, one thing has become abundantly clear: you can’t just copy-paste solutions. A one-size-fits-all approach doesn’t deliver. Each operation is different and various factors need to be considered–different orebody and ore types, geographical location, local environmental factors, local politics and culture, economic climate, local price pressures, company culture, market fluctuations, existing equipment and processes, historical practices, etc.

Successful mine-to-process optimization requires a detailed understanding of the ore types and all mine-to-plant processes. This is based on extensive data collection and analysis, modeling and simulation, combined with extensive industrial experience to identify solutions tailored to each operation. Understanding the orebody, the characteristics of the different types of ores, and how these will behave through the mining and processing stages allows the operating strategies in the mine and processing plant to be tailored and optimized. To get the best results for the business, each stage–mining, comminution, separation–must be optimized for the different ore types within the context of the entire operation.

And going into the future, what do you think the three biggest challenges for minerals processing will be?

I’d say the three biggest challenges would be: (1) lower feed grades and more complex mineralogy, (2) increasing water and energy costs and supply issues, and (3) social licenses. Let’s break them down:

Lower feed grades and more complex mineralogy

New deposits typically have lower grades, are more difficult to extract, and have more complex mineralogy. The challenge is how to extract the mineral resource efficiently and profitably. It’s essential to do more with less, to recover more value from low-grade and difficult mineral resources while minimizing impact. Mine-to-process optimization and geometallurgical modeling and forecasting are concrete steps towards addressing this challenge. And it may be possible to upgrade some low-grade and marginal deposits with pre-concentration to increase the economic viability, but this is very case-specific.

Increasing water and energy costs and supply issues

Lower grades require greater tonnages to be treated to deliver the same amount of product, which means higher energy and water consumption. Energy and water costs are rising, and in some cases, supply is also limited. It’s not practical, economically viable, or responsible to employ large-scale and non-selective processes to grind everything to a very fine size and let downstream processing sort it all out. Grinding is very energy-intensive. We should only grind as much material as is necessary. Early rejection of barren material has the potential to deliver significant energy and water savings and reduce the amount of fine wet tailings requiring disposal.

Social license to operate

We have always focused on extracting resources with minimum impact, and with growing societal pressure on the mining industry to minimize environmental harm, the search for more sustainable and efficient technologies and practices is becoming increasingly important. And for us, safety is always top of mind.

Can you talk to us a little bit about the path forward? What major innovations are set to pave the way?

We want to innovate in all that we do as we continuously strive for positive change. We work with many clients, suppliers, and technology partners to address any issues through developing and utilizing more efficient technologies to extract valuable minerals more economically and with less environmental impact.

Solutions can include a number of alternative technologies and operating strategies and it’s critical that they be tailored to the specific operation.

We’ve had great success over the years in mine-to-process optimization by adjusting the blast design and intensity according to rock characteristics. More blasting energy is applied in harder and blockier areas of the deposit to improve fragmentation and throughput of downstream processes, while less blasting energy is applied in softer and more fragmented areas where it’s not required, thus reducing costs. As technology and knowledge improves, even higher intensity and more selective blasting may further extend these benefits while still ensuring safe blasting practices.

In the face of lower grade deposits, which require mining and processing of much larger tonnages, pre-concentration offers hope. The aim is to reject barren material prior to energy-intensive and expensive comminution (crushing and grinding) stages. Pre-concentration can significantly improve economics by upgrading marginal and low-grade material and/or increasing production rates with the installed equipment and thereby also reducing water and power consumption. There are many options for pre-concentration (pre-screening, particle or bulk sorting, gravity concentration, flotation, magnetic separation, coarse flotation). But the upgrade performance is very case-specific, and many require significant ancillary equipment, feed preparation, and materials handling. It’s important to fully estimate costs and understand the impact on the overall operation to determine the best solution.

The design of energy-efficient comminution circuits is also a big one. Many circuits could be made to be more energy-efficient by modifying their design or operating conditions. Alternative comminution technologies such as HPGR, vertical roller mills, and stirred mills, and correct selection and operation of classifiers can significantly improve the efficiency of the overall circuit. But again, it’s important to consider the overall impact including all ancillary equipment, power, grinding media requirements, and final grind size etc., to ensure the best result for the operation.

Last, but not least, dry stacking of filtered tailings is becoming an increasingly common–and safer– consideration. Low feed grades make for large mines and large tailings dams which increases risk of failure. Dry stacking eliminates this risk and other benefits include substantially reduced water requirements, decreased risk of groundwater contamination, and a lower environmental footprint. The problem is, the very large tonnages of tailings that need to be filtered for stacking makes this very costly, but I understand that filter suppliers are working hard to develop filters with higher capacity and improved efficiency for treating very large tonnages of tailings.

Sounds promising. Innovation, efficiency, safety, and environmental impact should always be top-of-mind.

Absolutely. And, of course, it’s important to remember that solutions can come with their own sets of challenges, and the impact on the overall operation including all associated equipment and activities must be considered. But we continue to strive for positive change, to look for more efficient ways to maximize value and minimize impact.

Thank you for sitting with us, Kristy-Ann.

Thanks for having me!