Mine to mill series: New Solutions to the Old Mine-to-Mill Approach

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Today, mining companies need to speed up their rate of change to adapt to an increased societal and governmental pressure in a volatile market while addressing the challenge of resource scarcity. In this new series, we will question the standard mine-to-mill approach and provide insights to make it more efficient, value-oriented and sustainable.

The mining industry today is facing a number of new challenges that limit, and may even nullify the effectiveness of the strategies we have relied upon for many years. Coping with more complex orebodies at lower grades, adapting to new environmental and social regulations/ responsibilities, meeting intensified global demand for commodities within a volatile market – all of these make it essential for mining operations to rethink the way they have traditionally been operated. This includes investigating the use of available methods and novel techniques that can improve short- and long-term mining and processing performance and thereby maximize profitability through best utilization of ore reserves over mine lifespan. One such proven optimization approach is mine-to-mill, which has been used successfully by the minerals industry world-wide for more than 30 years now. Mine-to-mill optimization in brief Traditionally, minerals mining and processing were operated as separate silos: the mining stage focused on producing ore at a required rate and cut-off grade, while the process plant focused on treating ore as it was reported by the upstream. However, mining and processing share a series of sequential stages that interact with each other until valuable minerals are liberated from the gangue. Recognizing this interconnection, the minerals industry began a paradigm shift in the 1990s, moving away from silo-based cost minimization and toward value-driven optimization strategies. This new approach, known as “mine-to-mill”, formally links the mining and milling stages in order to unlock opportunities to improve overall productivity and profitability. Mine-to-mill demands optimal contribution from each stage to achieve the best performance across the value chain, rather than just realizing each silo’s distinct objectives. It identifies drill-and-blast as both the first step in comminution and a key leverage point where blast designs can be manipulated to produce more appropriate mill feed size distributions (generally finer in size) for improved downstream performance, specifically grinding capacity. The mine-to-mill approach has been widely implemented in number of mining operations across the globe, with documented productivity gains in the range of 5-20%. Four case study examples Several mine-to-mill optimization projects carried out in the 1990s and 2000s demonstrate how adopting an integrated approach can improve performance records and economic gains. For example: An Australian gold mine needed to remove a bottleneck at its SAG milling stage and improve the overall performance of its comminution circuit. Through mine-to-mill optimization, the mine tailored the SAG mill’s feed size by implementing high-energy blasts relative to standard blasting practice, which resulted in 10% throughput increase. A gold mine in Papua New Guinea also identified the SAG mill as a production bottleneck. By increasing the blasting powder factor from the standard 0.24 to 0.38 kg/t, the SAG feed P50 reduced from 75 to 35 mm, increasing SAG milling throughput by 15%. A copper-gold mine in Australia conducted an extensive optimization program that included field surveys, ore characterization, blast fragmentation modeling, comminution modeling, and simulations. Alternative blast designs, in conjunction with a closer crusher gap, improved SAG mill throughput by 12%. An Australian lead and zinc mine tested whether controlling ore cut-off grade could improve flotation performance. They discovered that removing 30% of “low-value” ore from the mine schedule reduced operating costs while improving recovery of silver, lead and zinc by 5.0%, 5.0%, and 2.0%, respectively.

 

What is “mine-to-mill optimisation approach?”

The mining industry today is facing a number of new challenges that limit, and may even nullify the effectiveness of the strategies we have relied upon for many years.

Coping with more complex orebodies at lower grades, adapting to new environmental and social regulations/ responsibilities, meeting intensified global demand for commodities within a volatile market – all of these make it essential for mining operations to rethink the way they have traditionally been operated.  This includes investigating the use of available methods and novel techniques that can improve short- and long-term mining and processing performance and thereby maximize profitability through best utilization of ore reserves over mine lifespan.

One such proven optimization approach is mine-to-mill, which has been used successfully by the minerals industry world-wide for more than 30 years now.

 

Mine-to-mill optimization in brief

Traditionally, minerals mining and processing were operated as separate silos: the mining stage focused on producing ore at a required rate and cut-off grade, while the process plant focused on treating ore as it was reported by the upstream.  However, mining and processing share a series of sequential stages that interact with each other until valuable minerals are liberated from the gangue.

Recognizing this interconnection, the minerals industry began a paradigm shift in the 1990s, moving away from silo-based cost minimization and toward value-driven optimization strategies.  This new approach, known as “mine-to-mill”, formally links the mining and milling stages in order to unlock opportunities to improve overall productivity and profitability.

Mine-to-mill demands optimal contribution from each stage to achieve the best performance across the value chain, rather than just realizing each silo’s distinct objectives.  It identifies drill-and-blast as both the first step in comminution and a key leverage point where blast designs can be manipulated to produce more appropriate mill feed size distributions (generally finer in size) for improved downstream performance, specifically grinding capacity.

The mine-to-mill approach has been widely implemented in number of mining operations across the globe, with documented productivity gains in the range of 5-20%.

 

Four case study examples

Several mine-to-mill optimization projects carried out in the 1990s and 2000s demonstrate how adopting an integrated approach can improve performance records and economic gains.  For example:

  • An Australian gold mine needed to remove a bottleneck at its SAG milling stage and improve the overall performance of its comminution circuit.  Through mine-to-mill optimization, the mine tailored the SAG mill’s feed size by implementing high-energy blasts relative to standard blasting practice, which resulted in 10% throughput increase.
  • A gold mine in Papua New Guinea also identified the SAG mill as a production bottleneck.  By increasing the blasting powder factor from the standard 0.24 to 0.38 kg/t, the SAG feed P50 reduced from 75 to 35 mm, increasing SAG milling throughput by 15%.
  • A copper-gold mine in Australia conducted an extensive optimization program that included field surveys, ore characterization, blast fragmentation modeling, comminution modeling, and simulations.  Alternative blast designs, in conjunction with a closer crusher gap, improved SAG mill throughput by 12%.
  • An Australian lead and zinc mine tested whether controlling ore cut-off grade could improve flotation performance.  They discovered that removing 30% of “low-value” ore from the mine schedule reduced operating costs while improving recovery of silver, lead and zinc by 5.0%, 5.0%, and 2.0%, respectively.

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Farhad FARAMARZI

Farhad FARAMARZI is a Senior Mining Industry Consultant at GEOVIA Dassault Systemes with over 10 year experience in Research, Consulting and Industry. Farhad holds BEng, MEng in Mining, and is specialised in Drill & Blast optimisation. He has worked in Drill & Blast specialist and superintendent positions - designed, led and surveyed over 100 full-scale production blasts at some large iron and copper open-pit mines. Farhad’s main area of expertise was built during his PhD in the Mineral Processing field at the Julius Kruttschnitt Mineral Research Centre (JKMRC) where he broadened his skillset and specialised in ore breakage characterisation, performance improvement, value-chain optimisation, modelling and simulation with several accomplished projects for Anglo American & BHP in this space.