Ore sorting is used in the early stages of mineral processing and essentially involves separating high-grade from low-grade materials. The technology behind ore sorting has evolved, meaning the process can now operate at higher throughputs and accuracy. Given these advances in technology, the question is: is ore sorting suited to your operation? And will it bring value to your mine?
Ore sorting has three key benefits: reduced processing cost per metal unit, reduced environmental footprint and increased throughput. By removing waste material early in the process, it eliminates costs associated with further processing. This also reduces the environmental footprint by using less energy, water, reagents and producing less tailings.
For comminution constrained operations, ore sorting can alleviate bottlenecks by reducing previously wasted capacity on low-grade materials, which can now be used for higher grade materials. For mining constrained operations, while improved sorting is not a significant lever for throughput it does provide the opportunity to convert previously uneconomic stockpiles into viable tonnes.
While there is a strong business case for ore sorting, the benefits need to be balanced against both the upfront investment and ongoing costs. There will be a significant capital expenditure requirement, which varies depending on the technology used for your operations. There will also be ongoing operational expenditure for the ore sorter, as well as additional operational complexity. While the ore sorter eliminates waste, it also introduces losses, and this affects the overall resource recovery.
There is a lot of activity in this space globally, both from miners trialling new equipment and industry vendors putting forward new developments. In a recent address at the Austmine 2019 conference, Anglo American identified bulk sorting as one of four technologies projected to unlock US$3-4 billion in gains by 2022 for their operations.
Anglo American has advised that these technologies reduce energy intensity by 10% as less reject gangue is being processed, having set up a full-scale demonstration facility at the El Soldado copper mine in Chile, which has further units scheduled to be delivered. A recent trial was conducted with CRC Ore’s ‘Grade Engineering’ at Sumitomo-owned Minera San Cristóbal operation in Bolivia. The preliminary results show a $451m profit and a 2 year increase of mine life opportunity through converting low-grade marginal and mineralised wastes to ore feed.
The recent developments in ore sorting are exciting, but it’s important to determine if ore sorting is going to deliver the required impact for your operation. There are three things you should consider:
Step 1: develop a value-driven approach to your business needs
Adopt a value-driven approach by determining the key value levers and sensitivities in your business (we recommend using a Value Driver Tree to visually map this out). From this, determine what initiatives (including ore sorting) are going to drive improvement. To drive maximum impact, these initiatives need to be prioritised based on value and ease of implementation. This will form part of the business case which will also need to factor items such as capital constraints and mine life.
Step 2: determine if the ore body is compatible
How ore sorting discards rock will impact recovery and sorter losses, which is dependent on your ore body characteristics. This is largely driven by how heterogenous your ore is i.e. 90% of metal contained in 50% of rock and ore sorted would make sense, however if 90% of metal stored in 90% of rock then the viability of ore sorting might need to be reconsidered.
Step 3: decide on technology to drive impact
Consider what ore sorting technology is best suited to your operation, from both a technical and financial view. Technically you need to consider what technology suits your metal, space and throughput requirements. Financially, you will need to determine which technology gives the optimal balance between the benefits and the capital/operational costs of ore sorting.