The imperative
Declining ore grades, water shortages and increasingly onerous environmental regulations around tailings are placing more pressure on mining companies to meet shareholder, community and societal expectations. Addressing these issues is no longer something that is nice to do, it is a must. Advanced mining technologies such as sensor-based sorting have recently matured and are primed to help solve these challenges.
What is sensor-based ore sorting?
Sensor-based ore sorting is a mineral pre-concentration technology in which particles or parcels of material are separated based on some physical or chemical property as measured or inferred by a sensor.
It is used to upgrade process feed by identifying and rejecting waste material early in the mining or processing systems (i.e. at the mining face, in the truck or on the conveyor). This results in pre-concentration of high value mineralisation into a lower gross volume of material.
Ore sorting exploits the heterogeneity (variability) of the orebody, which in many cases today is overlooked or blended out in the name of higher volumes and stable feed.
Benefits of sorting
Primary benefits obtained from ore sorting vary based on individual mine characteristics, but generally result in more metal production at a lower cost and lower environmental footprint. More specifically, benefits may include:
Unlocked plant capacity - through earlier rejection of waste material prior to processing
Increased plant head grade - by replacing rejected waste or low grade with higher grade material in the processing plant
Reduced cost per metal unit produced - through the increase in metal produced due to higher grade feed and the reduction in costs associated with processing waste or lower grade material
Reduced tailings volume - rejecting waste from ore at an early stage allows the mass of fine final tailings to be reduced and the associated storage space
Reduced carbon emissions, water and energy consumption - rejecting waste before the processing plant and upgrading the plant feed means less tonnes of ore treated in the processing plant per ton of product. This results in reduced water usage, energy consumption and subsequent carbon emissions per metal unit produced
Increased mineable reserves - rejecting waste from run of mine ore enables mining with a lower cut-off grade and a corresponding increase in mine life
Reclaimed ore from dumps and low grade stockpiles - bulk ore sorting (or particle sorting) may enable the recovery of valuable components from waste dumps, low-grade stockpiles and marginal reserves that would otherwise be uneconomic to treat
Reduced dilution and ore loss - if applied at the mining face bulk ore sorting can reduce dilution and ore loss
Optimised capital spend - in brownfields operations capital for plant upgrades can be delayed or eliminated. For greenfield operations, plant size can be reduced, or the production rate increased.
State of technology
Sensor-based ore sorting is not new to mining as particle based, low capacity sorting has been around for decades. These sorters (stream based sorting) require careful feed preparation, operate at limited size fractions and generally eject material with blasts of compressed air. The challenge has been in the adaption and application of the technology to bulk, high throughput use cases in harsh environments without introducing additional process steps (i.e. at the mining face, in the truck or on the conveyor). These challenges are now being overcome thanks to industry, government and entrepreneurial investment in research and development, increasing the attractiveness of bulk ore sorting applications in the mining industry.
Choosing a sensing system
Selection of the appropriate sensor or combination of sensors is based on several variables. These include but are not limited to the ore mineralogy and heterogeneity, how the ore is presented to the sensor, the desired throughput rate and the required accuracy. This is because different sensors have different depths of penetration, applicable size distributions, abilities to identify versus quantify ore properties and accuracies based on the target material and their specific operating parameters.
Sensing technologies that have been applied in various bulk and stream based sorting processes include:
Prompt Gamma Neutron Activation Analysis (PGNAA) and Pulsed Fast Thermal Neutron Activation (PFTNA) - measures elemental abundance based on gamma ray signatures from neutron scattering events
X-ray transmission (XRT) - classifies ores according to their specific atomic density
X-ray fluorescence (XRF) - measures elemental abundance based on fluorescence under x-rays
Colour camera - classifies industrial minerals, base- and precious-metal ores or gemstones by colour, reflection, brightness and transparency
Laser - measures reflection, adsorption and fluorescence of the laser light on crystal structures
Near-Infrared and Infrared (NIR/IR) - classifies and quantifies ore mineralogy according to their associated reflection, absorption and transmission spectrum profile
Hyperspectral - classifies ores according to spectral signature across a range of visible, near infrared and short, mid and long wave infrared bands
Magnetic Resonance (MR) - a form of radiofrequency (RF) spectroscopy that is used for quantitative measurement of target ore minerals
Laser-induced breakdown spectroscopy (LIBS) - detects elemental composition through the analysis of spectral signatures generated from high intensity laser pulses
Electromagnetic (EM) - classifies metals and ores in accordance with their conductivity and permeability.
Just as critical as the sensor, is the system and algorithms that convert the data into information used to make sorting decisions. Speed, accuracy, resolution, volume limitations and detection limits of such systems are key considerations that will impact selection.
Depending on where the sensing technology is positioned in the value chain and the capability of the sensor itself, additional process steps may need to be added to present the material in a specific way or divert material after it has been sensed. Adding process steps would require the addition of equipment such as grizzlies, feeders, sizers, diverters and conveyors.
Recent industry application
Bulk ore sorting is a key pillar in Anglo American’s “Concentrating the Mine” innovation theme that is looking to materially reduce the energy, water and capital intensity of mining. A 500t/hr system believed to use PGNAA/PFTNA sensing was initially trialled in El Soldado, targeting a 5% grade improvement and 20% increase in throughput. Based on positive results, the system is now in commercial production and two additional mines are targeted for implementation in 2020.
Newcrest is also investing in sensing and sorting technologies as part of their “Selective Processing” innovation breakthrough lever. Currently they are in a field demonstration phase with two trials at Telfer using PGNAA mass sensing and sorting and X-ray particle sorting systems. These are targeted to increase overall gold recovery, reduce processing costs and unlock lower grade inventories. Other trials are underway at Cadia that also include MR.
At Highland Valley Copper, Teck has implemented a shovel mounted sensor (XRF based) to aid in ore sorting and dilution reduction. This has been also been piloted at two of their other operations, Red Dog and Carmen de Andacollo. Also seeing value in sensor-based ore sorting, particularly at its Copper operations, BHP has been testing, trialling and implementing various XRT, XRF, PGNAA/PFTNA, MR and Hyperspectral technologies at its mine sites.
Size based particle sorting and screening also have the potential to produce major benefits. Sumitomo’s Minera San Cristobal successfully completed a full-scale production trial in partnership with CRC ORE. Once fully implemented it is expected to generate an additional AUS$450 million in profit for the mine and reduce its energy consumption.
Suppliers
Thee are numerous organisations that have experiece in providing ore sorting technologies, systems and research, some of whom are listed below.
Sensing technology providers:
Ore sorting systems:
Research organisations:
Where to start
To understand if ore sorting can successfully be applied at your operation and if it is something you should pursue, some of the questions you will need to answer include:
Does it align with our business strategy?
What investment hurdles and risk profile will it need to meet to progress?
How do we rapidly assess the suitability of our orebody (including its heterogeneity) and the potential value?
What cost and effort is required to realise the value?
What capability is needed to deliver the program and how will we get it?
How will ore sorting both integrate with and impact upstream and downstream systems and processes?
Email me at ben.jaggard@intifica.io to discuss how we can help you through the initial assessment process. Also check out our website at www.intifica.io to see other value adding services we offer.
Stay connected with the latest innovation news and insights
Sign up below to join our growing Intifica Insights community and receive monthly newsletters containing the latest technology and innovation news, actionable insights, upcoming events and more.
Showcasing solutions to your business problems.