ORE SORTING

Cutting comminution energy

down to even smaller sizes. [It] involves The industry needs to cut energy costs across the board, evaluating the mineral content of individual particularly in comminution. One way to do that is to rocks as they pass through the ore sorter and reduce the amount of waste rock that wastes energy by separating them into accept and reject fractions, based on predetermined selection criteria. being crushed and ground, John Chadwick investigates “By providing an economical way to reject sub economic grade materials at large particle ustralia's JKMRC recently surveyed the these results is presented. Ore sorting has been sizes, ore sorting is an ideal tool for: comminution energy requirements of gold identified as a technology with potentially broad n Making low grade ore deposits viable to Aand copper producing mines to provide reaching impacts on the industry. With the develop reliable benchmarking data which can be used implementation of ore sorting significant energy n Recovering valuable fractions from waste to compare comminution energy consumption savings or throughput increases are realised dumps across different mine sites. The study showed during comminution, and these effects are then n Accelerating cash flow and payback that comminution of gold and copper ores can felt throughout the plant.” n Removing nuisance materials e.g. talc be expected to consume about 0.2% of global, Orchard Material Technology (OMT) has been n Improving processing plant recoveries and and 1.3% of Australia’s electricity consumption. working extensively on mineral sorting efficiencies MEI’s Barry Wills notes that “the best way to developments for a number of years and says n Reducing transport & processing costs. reduce comminution energy is not to the technology “promises to revolutionise the “Depending on the size range of the material comminute, therefore concentrating the ore via economic outlook for metal mining and being sorted Applied Sorting can engineer gangue rejection prior to grinding is likely to processing by rejecting run-of-mine (ROM) machines to achieve throughput rates up to 100 achieve the largest positive effect on material after crushing that does not contain t/h per machine.” comminution energy efficiency. Dense medium economical target metal values. The only Machine sensitivity and the cut-off grade for separation has long been used to do this on crushed material sent to the milling and the accept/reject split can be adjusted so ore amenable ores, such as Pb-Zn vein deposits, but processing plant, and the only material to be sorting machines can generally be fine-tuned to electronic ore sorting is showing great potential, afforded significant additional energy and suit individual operating requirements e.g. high by identifying the metal values in a run-of-mine reagent investment, is the ore that contains a upgrade ratios or maximum recoveries etc. stream and separating the rock containing pre-determined fraction of the target metal The latest ore sorting development from valuable mineralisation from barren material. value. Applied Sorting is its X-ray transmission sorter, A US paper in Minerals Engineering provides Applied Sorting Technologies explains that intended primarily for upgrading the ores of quantitative discussion on the impact of this “ore sorting is a process for upgrading mineral steel alloying elements like tungsten, technology. “Dual-energy X-ray transmission bearing materials at large particle sizes, molybdenum, vanadium, nickel, manganese and was used to sort ore from different mines, and typically between 150 and 10 mm. Some chromium as well as several other high value an analysis identifying the economic impact of particularly high value materials justify sorting materials like tin, bismuth, tantalum etc.

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The system generates an X-ray X-Ray Transmission Sorting image for each rock as it passes OMT has specifically evaluated only through the sorter and uses high- run-of-mine (ROM) ore from operating speed digital image processing to mining facilities to assess different determine the amount of the potential sorting technologies. After desired mineral within each rock. It extensive geologic, petrographic, and has the advantage of not relying on analytical testing, sorting campaigns rock surface information, unlike were conducted to identify the alternative sensing methods which potential for automated sorting, rely on surface optical fluorescence evaluating these techniques in detail. or light reflectance properties to (1) Optical Sorting indicate grade. Instead, it (2) Microwave/Infrared Sorting effectively measures the weight of (3) Dual Energy X-Ray Transmission the valuable material contained Sorting within each rock and computes the (4) Laser Induced Breakdown corresponding rock grade. Applied Sorting installation at Leinster (nickel, Spectrometry (LIBS) X-ray transmission sorting is highly effective Western Australia) “All four technologies were extensively in ores where the mineralisation occurs as evaluated, but Dual Energy X-Ray Transmission particles or lenses within the rocks being mining´s toughest problems. Next generation showed significant promise as applied to the sorted, even if they are only a few millimetres in mining requires collaborative breakthroughs.” subject planar vein structured molybdenite size. The X-ray system is able to look inside the TOMRA was chosen as an expert partner for deposits.” rocks, add up the weight of the valuable sensor-based solutions for gold ore sorting. The recent case study conducted by OMT on particles and decide whether a particular rock Hartmut Harbeck, Technical Director, comments: an operating molybdenum resource determined should be accepted or rejected. “This partnership will allow us to network with that 98.9% of the total molybdenum contained Applied Sorting says it can quickly assess the exclusive partners and share knowledge.” in the ROM ore was present in only 28% of the suitability of particular deposits or stockpiles for Last year TOMRA began a strategic crushed ore (20-80 mm size). ore sorting by running trials on small samples of partnership with Rio Tinto to develop “This work provided the necessary impetus to crushed rock or drill core. commercial scale sorting systems for upgrading identify a technology capable of (a) ‘seeing’ the Another specialist supplier in this field, bulk minerals. At the time the company noted molybdenum in the stones in a manner that did TOMRA Sorting Solutions, has become a that “currently there are no solutions in the not require significant energy investment, (b) member of the international AngloGold Ashanti market that fulfil Rio Tinto’s specifications for a differentiating between stones with Technology Innovation Consortium. The requested platform. A dedicated R&D program molybdenum and stones without, and (c) consortium, based in South Africa, was will therefore be initiated by the two partners to providing a means of sorting out those stones established in 2011 by AngloGold Ashanti and, develop an adequate solution. identified as containing molybdenum from those including TOMRA, comprises 46 industrial “This work will include scaling up Rio Tinto’s that did not. In terms of total energy investment, companies, eight universities and research iron ore and copper sorting technologies crushing is far less costly as compared to institutions all of which are seen as innovators IronX™ and NuWave™ - which convert milling. As such, it is reasonable to expect a in their field. The aim of the consortium is to potentially waste rock into a commercially mineral sorting operation to act on the ROM ore create new ways of thinking and new valuable resource – to have each machine stones as it exits the crushing circuit.” opportunities for deep level mining. capable of sorting 1,000 t/h of rock. TOMRA In the study discussed here stones sized in Mike MacFarlane, Senior Vice President Sorting Solutions has previously been a key the range of 20-80 mm were used. Technical Development at AngloGold Ashanti supplier to both IronX and NuWave. In cooperation with wTe Corp ( a recycling says: “The consortium facilitates solutions by It is a leading provider of sensor-based company outside Boston, Massachusetts) a bringing the world´s leading innovators to solve sorting solutions for optimal resource bench scale test rig consisting of an X-ray productivity and has source, a dual energy X-ray transmission (XRT) provided state-of-the- detector, and a rotating ‘swing arm’ sample art sensor-based holder capable of simulating conveyor belt sorting technology for speeds was constructed and calibrated for this dry material separation test program. Individual stones were passed in various minerals and through the X-ray beam and their XRT profiles ore applications since were collected by computer. A series of 1988. computer image processing algorithms were then performed to determine the relative content of molybdenum in each stone. OMT explains that “XRT functions much like the X-ray one would receive in a doctor’s office; as X-rays pass through a material they are either TOMRA Sorting Solutions installation at absorbed, reflected, or transmitted. The level of Gold Fields’ Kloof gold transmission is dependent on the density of the mine: PRO Secondary material; therefore, denser metals (like COLOR molybdenum) will transmit less X-ray energy

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than lighter metals (like silicon, iron and Mine A XRT thresholds: recovery versus rejection aluminium). The dual energy XRT detector measures the amount of X-ray energy passing through the sample and converts it into a grayscale image indicating the degree of transmission pixel by pixel. Because the host rock in many refractory metal ores is comprised of silica, aluminates and similar light minerals, differentiation between the heavy refractory metals and lighter host rock is possible. The heavy refractory metals appear dark under XRT while the host materials are lighter. “However this work is complicated because we are looking at various sizes and shapes of crushed stones. Stone thicknesses ‘point to point’ across the surface has a very significant effect on the ‘perceived’ density of these samples. In most applications of this technology this random thickness effect is a serious problem. In our work we are able to adjust for variations in sample thickness and sample contour through the application of the Dual Energy “A second campaign of mineral sorting using “The ROM material studied from Mine B had a sensor and computer algorithm technologies. the same test rig was carried out on Mine B, head grade of 0.058% Mo; therefore, at the Also, since we are dealing with the speeds of an which was also an operating molybdenum mine different thresholds used in this study, the feed X-ray beam and the decision making speed of a with very different geology from Mine A. In a to the milling and flotation circuits was enriched powerful computer these effects are handled and similar manner to previous studies, individual by a factor ranging from 4.5 to 15 while an ‘Accept or Reject’ decision can be made in stones [448 in number] were sorted using the decreasing the mass flow by 37-91%. milliseconds. This is a very important capability. Dual Energy XRT instrument and computer Furthermore, the material rejected as waste “In our previous study we investigated three algorithms. In this work, however, four thresholds contained molybdenum that is likely below the different thresholds of sorting rigor on the ROM were used: relaxed, moderate, aggressive, and cutoff grade at most mining operations. Anyone material from Mine A. Individual stones [1,301 in uber-aggressive. The added ‘uber-aggressive’ familiar with the operation of molybdenum number] were examined. When the computer threshold was developed to study an upper mining projects understands that in the usual algorithm analyses the image of a given stone, it limiting case of just how much molybdenum ROM material from the primary or secondary counts the number of darker pixels it sees in could be recovered and at what mass-rejection crushing circuit a few of the stones in the pile are each image. The level of rigor the threshold cost. The relative rejection rigor of the four essentially massive ‘chunks’ of molybdenite. OMT requires then determines how many dark pixels thresholds was similar to the thresholds used the computer algorithm to identify these must be identified in an image in order for the previously used; i.e. ‘relaxed’ required a higher particular stones and learned that it could recover: stone to be classified as containing our target count of dark pixels, while ‘uber-aggressive’ n 40% of the total molybdenum in <0.9% of the metal, in this case, molybdenum. In the study of required the least.” ROM material Mine A, the ‘relaxed’ threshold required many dark pixels while the ‘aggressive’ threshold Mine B XRT thresholds: recovery permitted fewer dark pixels in order to gain a versus rejection positive molybdenum-containing classification. As a result of these thresholds, it was expected that while more molybdenum would be identified (i.e. higher total recovery) at the ‘aggressive’ threshold, this would also increase the number of false-positives (i.e. stones identified as containing molybdenum but not actually having any economical levels of molybdenum).” “Even with the ‘aggressive’ threshold, >66% of the total ROM ore was rejected as not containing economically recoverable levels of molybdenum; this threshold also resulted in >93% total molybdenum recovery. The ROM average molybdenum content (grade) in this material as a whole was 0.04%. “Therefore, one benefit of this mineral sorting effort was the effective upgrading of the material’s head grade going to the milling circuit; an upgrading factor of circa 3-9 was realised in this study.

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REDWAVE C sorting - material flow: 1. under recognition of individual response to vibration conveyor 2. light source 3. camera unit 4. ejection unit and 5. divider colour, density, shape, conductivity, size, plate surface texture, thermal transfer, transparency, electromagnetic induction and n 57% of the total molybdenum in X-ray transmission.” <1.6% of the ROM material Comex notes key benefits of: “These particular stones represent the most n High separating efficiency up to 99.9 % economically valuable stones in the ROM stream. n Complete 2D/3D analysis of particle The algorithm is able to accurately identify them geometry as the stones to mill on a ‘rainy day’ because n Possibility for on-site waste material they constitute an enormous separation molybdenum value at a fraction of the n Possibility to separate materials by cost. This might be considered a fifth, recognition of many different properties in the ‘extremely relaxed,’ threshold. same unit. “In summary, the work completed by OMT in Advanced sorting based on 2D particle scan; this study demonstrates that a significant request the OSX-1000 can separate particle sizes of 15- reduction in the energy expenditure in the milling in 2012 for elimination of these contaminants 300 mm at capacities of 5-250 t/h. Its standard and flotation circuits of a molybdenite processing through a sensor-based sorting machine. size is 7.1 m long, 2.5 m high and 1.7 m wide. It plant is possible without sacrificing economically This resulted in several successful sorting offers multi-parameter sorting and a sorting viable metal recovery. In studies conducted on trails being conducted by BT-Wolfgang Binder in efficiency of up to 99 %, Comex reports. two different mines, the total amount of ore collaboration with the customer. A visit was also And on 3D particle scan, VSX can separate processed in the milling circuit can be reduced by made to the Leube company in Golling, which particle sizes of 20-300 mm at capacities of 5-40 >30-60%, meaning a reduction in the capital already has REDWAVE mineral sorting machines t/h per line. The standard size is 10+ m long, 1.8 expenditure in the mills and/or a significant in use for two years. lt was also possible to m high and a width of 0.6 m/line. Features increase in the operating capacity of an existing successfully implement the customer include detailed full 3D scan of the particles, mill. Many other additional benefits to the overall requirement to install the sorting machine sorting efficiency up to 99.9%, unlimited number capital costs, energy costs, reagent costs, directly onto the existing screening machine and of fractions and the possibility to connect parallel manpower costs, and maintenance costs of ore thus have minimal influence on the operation. lines. processing will also be realised through the This facilitated the minimisation of additional Comex offers an iron ore case study as an successful implementation of these advanced costs as well as savings in space. The mineral example. It assumes a material stream out of the mineral sorting technologies.” sorting machine has been in successful operation mine at 500 t/h. This stream has a waste material separating impurities from quartz since June content of 30 % and enters the OSX, which in this Economic ideas 2013. These contaminants can be readily case has a separation efficiency of 90 %. REDWAVE C is an optical sorting system using identified and sorted with the REDWAVE 1300 S “A typical iron ore processing plant used about colour recognition. For mineral sorting, the (mineral sorting machine). The installation of the 315 kWh/t iron ore. By implementing OSX into machine is equipped with a high-resolution RGB machine and the adaptation of the existing plant the existing iron ore plant facilities; you can camera. The sorting width is 600 mm to 2,000 were carried out by the client. achieve huge cost savings: mm and the capacity depends on material and The owners, Joachim and Fritz Feichtinger, also n Energy consumption reduction -26% grain size. Feed Band (single-sided detection) or commented that: "We have been very impressed n Waste disposal reduction after processing -90 chute (two-sided detection) systems are with the REDWAVE technology and the existing % available. established system at Leube, and we are very n Reduced transport requirement from the mine Infeed material is spread over the entire pleased with the sorting equipment." to the plant -27%. REDWAVE sorting width by a vibration feeder or Comex offers “complex and robust optical An example gold case study has a material an acceleration belt. The material is then scanned sorting systems, in a user-friendly platform, for stream out of the mine at 100 t/h. This stream and identified by the sensor system (single or the identification and sorting of particles based has a gold bearing material concentration of 20 double sided sensing), while in free fall. If the on different physical properties. This is achieved %. The material stream enters the OSX, which in identified minerals meet the set ejection parameters, a signal is sent to the ejection units. Individual high speed air jets, operated by compressed air, eject the identified mineral. The number of activated solenoids depends on the size of the identified particle. Feichtinger is a private company from Esternberg (Upper Austria) and provides some 30,000 t/y of quartz to the RW Silicium company. The company has been active in the mining of quartz since 1972 and currently employs 18 staff. Due to more stringent customer demands it became necessary to sort out impurities (the green and red stones) in high quality quartz. Illustration of the Comex CXR Consequently, Feichtinger issued a tender separation system

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this case has a separation efficiency of 80 %. sulphidic rocks stick (somewhat) to the belt, the beneficiation plant. QuarCon measures elements. “By implementing OSX into the existing gold silicates/carbonates do not, hence creating OreSpex enables fast ore mineral and rock processing plant facilities, you can achieve huge different discharge trajectories. A proof of identification. Both instruments facilitate the savings when it comes to energy consumption concept model has been successfully operated control of dilution and grade in the mine. IM and waste disposals: and an exploratory demonstration machine is n Energy consumption reduction - 67% now under construction at Humber College in n Waste disposal reduction - 64%. Toronto. “Let us assume that we have the same German ore sorting equipment manufacturer material stream into the processing plant as Steinert has also joined the project. before (100 t/h). However by using the OSX, we upgrade the gold bearing material concentrate Leave it in the pit from 20 to 56%. In this configuration, it is Of course another way of reducing the amount of possible to increase the gold production by waste in the processing plant is to leave it in the 180%.” mine. Atlas Copco plans to offer a device for bench drilling that enables open-pit mines to Microwave sorting track and analyse valuable minerals while drilling Gus Van Weert, Adjunct Professor at UBC and is in progress. President ORETOME Ltd is exploring the The OREalyzer, based on technology from IMA phenomenon that sulphides, being semi Engineering, is integrated into Atlas Copco’s conductors, heat up in a microwave field while SmartROC D65 drill rig. It pinpoints the location silicates and carbonates do not. of the ore, analyses its quality and identifies However, he cautions that the waste boundaries while drilling is in progress. microwave/infrared sorting approach suffers Olav Kvist, Product Portfolio Manager at Atlas from the same problem as all the other sensor Copco, says: “By knowing exactly where the ore based machine sorters: they are relatively is located, the mine can potentially get far better expensive to operate. This is due to the use of ore recovery. This means that mines can extract compressed air to blow the desired rock fraction more value from the blasted material and into a different trajectory. That costs several increase the amount of sellable material in the dollars per tonne sorted. When one sorts bench.” diamonds, it is affordable. There are also many Log files are sent automatically to the mine cases in the processing of industrial minerals office through the RRA (Rig Remote Access) where machine sorting is (highly) profitable, option, enabling early decision-making on blast because the value of the product is often in the design as well as loading priorities. In addition, hundreds of dollars a tonne. the OREalyzer reduces the need for personnel to “Gold or base metal ores are generally worth collect and handle samples on the bench which tens of dollars a tonne, in the low range for increases safety. open pits, in the high range for The OREalyzer can be used with both DTH as underground mines. Sorting these ores well as RC drilling and integrates with acQuire costs more than it saves in production databases. It is available in two processing/milling. different versions, covering both production “Microwave/IR machine sorting has not drilling and in-pit grade. Kvist continues: “The offered a solution to the problem of product strategy is one of empowering the local costs and since it has not been shown geologist with a new tool, turning the drill rig into (yet) to be applicable to industrial a sensor. This will revolutionise the way mines minerals sorting, sorting equipment create value.” producers have ignored the The Blast Hole Sampler-Analyzer is the newest technology. However, it has been IMA development and uses the most advanced reported that Rio Tinto has spent analysis technologies. These analysers are millions of dollars exploring the capable of taking representative samples, possibilities in a pilot plant in measuring the samples and displaying analysed conjunction with Nottingham values in real-time. University in the UK.” IMA Engineering is Van Weert is now trialling a well-known for its demonstration/ research ore sorter QuarCon (XRF) which does not use expensive and OreSpex sensors, or the costly operating (LIF) cross belt expenses of air blasts. The principle analysers that is simple. Sulphide ore passes are used to through a microwave oven/zone and monitor ore falls on a belt, coated with quality on thermoplastic adhesive. The warm conveyor belts in the mine before the

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