Ore Stream Research Articles

A bulk sorting trial of copper ore using a magnetic resonance analyser

Sensor-based bulk ore sorting (BOS) is a technique that may lead to uplift of processing grades by excluding waste as well as an increase in usable resource by sorting material designated as mineralised waste. A magnetic resonance analyser (MRA) was installed on the primary crushed ore feed to the sulphide plant at the Kansanshi copper mine in northwestern Zambia to trial BOS. The conveyor belt operated at 2800tph and carried ore of which greater than 85% by weight of the copper-bearing minerals are chalcopyrite. The MRA was therefore tuned for chalcopyrite’s zero static field magnetic resonance. The analyser achieved a 3σ detection limit of 0.045 wt% copper as chalcopyrite over a 4 s measurement time and standard belt loading, with lower detection thresholds possible if the measurement time increased.A trial of ore diversion was then carried out at the site. Pods of ore measured as less than 0.2 wt% copper as chalcopyrite by the MRA were diverted by a dead box diverter system to form a low-grade stockpile of approximately 10,000 tonnes. A cavity in the mill feed stockpile was arranged and the rejected material fed back through the crusher, past the MRA and directly through the milling circuit to the flotation feed where a Vezin sampler was used to take a sample every 5 min. This sample was then tested for copper grade by the site metallurgical laboratory. The MRA measured a grade of 0.16 wt% copper as chalcopyrite over the test time period and the Vezin samples for the last hour of the trial reported approximately 0.2–0.3 wt% copper despite some mixing with unsorted ore being inevitable. This is as clear a demonstration of bulk ore sorting (BOS) as practically achieveable in the production environment at Kansanshi and, to the author’s knowledge, the first demonstration of BOS on a copper ore stream of at least this throughput.

ASSESSMENT OF THE COMPLEXITY OF OCCURRENCE AND GEOLOGICAL VARIABILITY OF THE QUALITY OF HIGH-GRADE ORES DURING THE DEVELOPMENT OF THE C-2 DEPOSIT

The work is devoted to a very topical issue - predicting quality indicators in underground mining of ore deposits. In this work, the conditions and ways of improving the quality of ores during mining were studied on the example of deposits of rich ores in the northern flanks of the Talnakh and Oktyabrsky deposits of Talnakh. The studies were carried out in specific conditions at the mining enterprises of the Polar Division of the Public Joint Stock Company Mining and Metallurgical Company Norilsk Nickel.
 The northern deposits of the Talnakhskoye deposit represent the main prospect for replenishing the retired production capacities for the extraction of high-grade ores. The significant heterogeneity of the distribution of the metal content in industrial reserves of rich copper-nickel ores is the primary cause of high fluctuations in the quality of ore flow, which requires the use of the most advanced mining technologies to control the quality of ores during extraction.
 The process of forming the required quality level of mined ores at the mines of the Polar Division of PJSC MMC Norilsk Nickel is of paramount importance. However, during the development of deposits of «rich» ores in the ore stream «mine - processing plant», significant fluctuations in the quality of the ore mass are formed, which lead to losses of metals in the process of concentration and during metallurgical redistribution, thereby reducing the economic efficiency of the entire mining and metallurgical complex, as determines the relevance of the work.

Stratigraphy and mineralogy of tailings at Macraes gold mine, southern New Zealand

ABSTRACT Processed tailings in the Mixed tailings impoundment at the Macraes gold mine built up a sedimentary pile up to 100 m thick between 1990 and 2013. The tailings consist of sand-dominated fluvio-lacustrine sediments with fine (cm scale) bedding and have a mineralogical stratigraphy that reflects changing mine processes. Most of the tailings (>90%) consist of silicate minerals discarded from the flotation system throughout that time. The deepest tailings (1990–1993) have the lowest contents of sulphides as these were extracted and deposited separately. Between 1993 and 1999, tailings with up to 0.5 wt% sulphide sulphur (as pyrite and arsenopyrite) were deposited. Introduction of a pressure oxidation system in 1999 caused a substantial decrease in sulphide minerals and a parallel increase in ferric oxyhydroxide, ferric sulphate, and ferric arsenate compounds in which trace metals are dispersed. Some primary scheelite reacted during pressure oxidation conditions to form ferric tungstate compounds. Processing of auriferous sulphide concentrate from Reefton, western South Island, from 2007 introduced stibnite to the ore stream, and this was readily oxidised to form insoluble As-bearing ferric antimonate.

Upconversion Fluorescence in Naturally Occurring Calcium Fluoride.

Fluorine can negatively interfere with leach and smelting processes during mineral processing. Real-time knowledge of the concentration and mineral hosts of fluorine in a mineral processing ore stream is important to protect process line equipment and product. Currently only offline methods of detection are available. Online sensors that determine specific fluorine-bearing mineral concentration in real-time would enable improved efficiency in processing decisions during mine production. Common excitation wavelengths used for fluorescence studies in minerals frequently provide signals that are not clearly host-specific, and hence of limited utility for mineral identification. We show that upconversion fluorescence, a process in which two or more photons are absorbed and one higher-energy photon is emitted, provides a more host-specific fluorescence output, minimizing spurious signals in complex environments and therefore greatly improving detection thresholds. Natural samples of fluorite (CaF2), a major fluorine host at many mine sites, have been analyzed by near-infrared excitation and have revealed upconversion fluorescence from rare earth inclusions. Upconversion fluorescence was detected in samples with rare earth concentrations as low as one part per million and is therefore considered a potential new sensing modality for real-time fluorite monitoring.

Investigation of Grain Size Distribution of Conveyed Copper Ore for Modelling Ore Flow through a Bunker

Knowledge of the particle size distribution of mined ore enables improvement of the main processes of the whole mining value chain: blasting, ore loading and haulage and ore processing. Photogrammetry with image analysis techniques was proposed for the on-line identification of grain size distribution of conveyed ore. Preliminary laboratory tests were performed on the experimental belt conveyor to evaluate the quality of photographs for various camera settings. Grain size distribution of transported copper ore was determined on the basis of photographs taken over the main haulage conveyor that feeds mined material to the underground ore bin located at skip-filling station of the winding shaft. Size distribution slope was calculated using the Split Desktop 4.0 software package to estimate the degree of rock fragmentation. Fine fractions (<10 mm) accounted for more than 40% of transported bulk material. Such a large portion of fine fraction may be attributed to the lithology of conveyed material. Individual rock lumps 600 mm or larger constituted a minor part of the total amount of mined ore. The actual ore granulation influences ore flow through the bin, which was simulated using a discrete element method model to obtain information about the ore stream leaving the winding shaft.

Influence of Magnetization Options on Detection of Unwanted Inclusions in the Tonnage of Iron Ore

Two options for constructing an attached induction transducer for detecting steel objects in an iron ore stream on a conveyor belt are compared theoretically and experimentally. The options in which testing covers the entire conveyor belt width and where the stream width is divided into “tracks” are considered. A significant effect of magnetic interaction between rock particles magnetized by the eddy current transducer field is revealed. It has been shown that magnetizing ore stream locally can provide substantially better conditions for the selective detection of undesirable steel inclusions in the iron ore stream than across the entire stream width. However, the latter option is feasible only given certain proportions between the transducer dimensions and the conveyor belt width. The results of experimental verification are in satisfactory agreement with theoretical estimates.

Copper Ore Quality Tracking in a Belt Conveyor System Using Simulation Tools

The ore quality at mining faces in the KGHM underground copper ore mines can be determined based on channel samples and block models built in the Datamine system. Unfortunately, even very accurate information regarding the quality of deposits at mining faces does not translate into the possibility of predicting the composition of feed to enrichment plants. The mixed ore from mining faces is cyclically loaded by trucks onto belt conveyors, which in turn convey it to shafts. When transported on the conveyors, mixed ore portions from many loading points form a divisional stream, which then goes to the main haulage conveyors where ore streams from various divisions are combined. The way of filling the bunkers, as well as ore flow temporary stoppages, changes the sequence of ore mixing and its arrival, which hinders the ability to track its quality. In the current study, radio-frequency identification (RFID) was proposed for tracking ore composition. A complementary method of ore quality prediction comes from simulating the tagged ore flow within the FlexSim software package. The discrete element method (DEM) of simulations, verified by experiments with RFID tags, can determine the ore flow through bunkers. Forecasts of ore feed composition for the next shift can be prepared with actual plans of mining division operations, the filling level of bunkers and the work plan of the transport system.

Improving high voltage pulse selective breakage for ore pre-concentration using a multiple-particle treatment method

High Voltage Pulse (HVP) comminution has the potential to be used in ore pre-concentration. Mineralisation after HVP breakage is concentrated into the finer sizes and size separation can then be used to produce high and low grade ore streams. Previous work on this technique has been performed using a single particle (SP) testing method where HVP energy is applied to every single particle. This paper presents an improved method where HVP is applied to multiple particles (MP). The MP method gives HVP the “freedom” to differentiate between particles and selectively only break those containing mineralisation. The MP method is shown to result in better mineralisation deportment into the finer sizes, at a lower specific energy, than the SP method of HVP application. This enables higher metal recovery and waste rejection rates during ore pre-concentration. HVP MP breakage consumes more energy but generates a better ore pre-concentration result than mechanical breakage. The ways to further enhance HVP selective breakage using the MP method are discussed.

MANAGEMENT OF PROCESSES FOR ENRICHMENT OF COPPERMOLYBDENUM ORES USING QUALITY CONTROL QUALITY

In the process of ore beneficiation, applying open control loop systems using ore quality as input parameter, proves very effective. To determine the ore quality, on-line analysis of its material and mineralogical composition, impregnation of valuable components is carried out. Based on the analysis results, ore streams are formed at the processing plant, and effective processing conditions are selected. Modern systems of visual metering analysis of ore create the basis for efficient automated control of beneficiation processes, based on the principle of advanced control of ore grade. To improve the accuracy of determining the ore mineral composition, a special installation has been developed, which provides cleaning of ore from slurry. The installation enables achieving high accuracy of the ore mineralogical composition analysis. Tests of the ore grade visual metering analysis system, carried out using copper-molybdenum ores of the Erdenet GOK, have shown high reliability and efficiency of the system.

Unplanned dilution and ore loss prediction in longhole stoping mines via multiple regression and artificial neural network analyses

In recent years, stoping methods have been magnified as an extraction strategy in underground hard rock mining. According to a report from Austrade (2013), in 2013 70% of underground metal mines in Australia utilized open stoping, sublevel stoping, various narrow stoping methods, and other types of stoping and caving methods to extract ore. In addition, 51% of underground metal production in Canada relies on open stoping methods (Pakalnis et al., 1996). A disadvantage of popular stoping methods is that many mines are severely affected by dilution problems. Pakalnis (1986) surveyed 15 open stope Canadian mines and concluded that 47% of the operations suffered from more than 20% dilution. Likewise, Henning and Mitri (2007) reported that approximately 40% of open stoping operations in Canada suffered from 10% to 20% dilution. Dilution can be defined as ‘the contamination of ore with lower grade material’, and it can be generally classified into two categories: planned and unplanned. Planned dilution, also referred to as primary or internal dilution, is contamination by low-grade material within the ore block; whereas unplanned dilution, also known as secondary or external dilution, is contamination by lower grade material exterior to the ore block. Both of these dilute the ore stream value. Ore loss can similarly be classified as planned and unplanned. Planned ore loss represents the ore-grade material that has been excluded from the mining block at the stope design stage, whereas unplanned ore loss is the part of the mining block that remains in the stopes after mining. This study includes unplanned dilution and ore loss, which can be attributed to as overand underbreak in underground stoping production. These phenomena can be divided into dynamic and quasi-static types; the quasistatic type occurs after blasting, while the dynamic type occurs immediately (Mandal and Singh, 2009). The dynamic overand underbreak types are the main interest of this study, and a new terminology, ‘uneven break’ (UB), is used to identify it. To extend the definition of dilution, UB can be defined as the tons of mined unplanned dilution (positive) or ore loss (negative) per ton of ore mined, expressed as a percentage.

Rejecting phosphorus in hematitic iron ore streams: is flotation the best approach?

It is widely known that steel made from iron ore pellets high in phosphorus is brittle. Removal of phosphorus from iron ores such as hematite has proven to be difficult. The majority of research on phosphorus removal from hematite ores has been focused on flotation. The purpose of this study was to assess phosphorus distribution under current operations at an existing hematite concentrator and determine how efficient the plant is at removing phosphorus. Objectives included: (1) Perform a phosphorus balance at an operating plant to assess phosphorus distribution under current operations; (2) Determine phosphorus removal efficiency of each separating unit and (3) Perform a quantitative liberation analysis to determine max phosphorus removal by physical means. Liberation was quantitatively determined using wet high intensity magnetic separation (WHIMS) to separate iron ore from liberated apatite (and other nonmagnetic compounds). It was observed that 61.2% of the total phosphorus entering Plant F was rejected during current operations. The desliming process was the most efficient step at removing phosphorus (45.1% P removed), whereas the flotation step was much less effective (16.1% P removed). Liberation analyses indicated that the deslime thickener may have been more efficient at removing phosphorus than the flotation circuit due to the greater abundance of liberated phosphorus in the deslime thickener feed. The scavenger returns stream was identified as having a high concentration of phosphorus and a possible point of phosphorus removal. However, liberation analyses indicated that only 32.4% of the total phosphorus in the stream was liberated. Grinding the scavenger returns to 80% passing 5.2 μm increased the amount of liberated phosphorus in the stream to 70.4%.

Reconciliation principles for the mining industry

Reconciliation involves the collection of tonnage, grade (quality) and contained metal (product) data from disparate and hopefully independent sources. Examples are exploration data, production sampling data from blast holes or draw points, and process plant data. These data may be compared by means of ratios (factors). The F1 factor usually relates short term (ore control) model tonnages, grades and metal content to ore reserves depleted. The F2 factor usually relates received at mill (measured by the mill) tonnages, grades and metal content to delivered to mill production tonnages, grade and metal content. The F3 factor is F1×F2 and enables a comparison of a mine’s (measured by mine) ability to recover the tonnage, grade and metal content estimated in ore reserves. The F1 factor measures the accuracy of orebody knowledge in the ore reserves to the demarcation of ore and waste by ore control (short term model). The F1 factor may be used to check and calibrate the selectivity of mineral resource models and/or planned dilution assumed in transfer from mineral resources to ore reserves. The F2 factor enables a check on unplanned dilution entering the ore stream between ore control and the mill. By using the factors it is possible to calculate a monetary value on improvements in the accuracy of orebody knowledge, selectivity and the effects of dilution and ore loss. Reconciliation should be an implicit part of the mining process, and reconciliation targets should be a key performance indicator for well run mines.

Comparative analysis of algorithms for processing mineral luminescence signals in the task of detecting diamonds in an ore stream

Results are provided for modelling in a Mathcad medium digital algorithms for processing signals obtained in diamond x-ray luminescence separators with continuous excitation. An estimate is given of the effectiveness of these algorithms and they are compared with analog traditional methods of signal processing. The question of temporal resolution of mineral luminescence signals is considered.

Quantitative measurement of copper mineralogy using magnetic resonance

A prototype instrument using magnetic resonance has been constructed for quantitative measurement of selected copper minerals, in bulk samples obtained from a number of commercial ore deposits. The instrument has been developed to provide rapid on-line determination of phase concentration. The on-line measurement of copper mineral phase would be of considerable assistance to the mineralogist or process engineer for process optimisation. Ultimately, the underlying method may be applied in ore streams on conveyors or batch samples. This paper describes the development of the instrument and measurement methods, with particular emphasis on chalcopyrite, focusing on the design route for instrument deployment. Quantitative results regarding detection limits and accuracy for dilute ore concentrations are presented. In addition, effects due to crushing and grinding are discussed. Owing to the very high selectivity of the technique, it has been possible to demonstrate mineral phase resolution of 0.1 wt% in bulk samples.

Mineralogical imaging of kimberlites using SEM-based techniques

Rapid mineralogical identification via energy dispersive spectrometer (EDS) equipped scanning electron microscope (SEM) techniques, is usually used to derive mineralogical images of finely comminuted particles of metalliferous ores. EDS-SEM techniques are shown below to also be suitable to the detailed mineralogical imaging of primary diamonds ores, i.e. kimberlites. However, certain characteristics of kimberlite such as the heterogeneity of the deposit, the relatively large particle size of the ore streams, the fine-grained silicate mineralogy, and the extreme rarity of diamond, present challenges to the imaging of these ores using such techniques. The estimation of standard process mineralogical parameters such as association, liberation, and grade, are therefore also complicated substantially. Potential solutions to these challenges include the presentation of larger samples to the instrument and the use of liberation and grade proxy minerals. Other uses of mineralogically classified images are also discussed.

High Tech Trash: Digital Devices, Hidden Toxins, and Human Health

By Elizabeth Grossman Washington, DC:Island Press, 2006. 334 pp. ISBN: 1-55963-554-1, $25.95 In High Tech Trash, Elizabeth Grossman traces the effects of the high-tech computer industry on the environment, from the raw materials to the chemicals and solvents used to produce silicone chips as well as other persistent organic compounds used to produce high-tech equipment. Grossman then describes the subsequent recycling of electronics for reuse as well as the recovery and recycling of raw materials such as copper, zinc, gold, and plastics. This journey through electronics, which formerly had been recognized as a “clean” industry, begins in the mines that supply many of the raw materials—including copper, aluminum, lead, gold, zinc, nickel, tin, silver, and iron—used in modern electronics. Grossman then discusses the different chemicals and solvents used in the production of silicone chips. She gives a close-up view of the electronics industry, recognizing the improvements in chemical safety from the early days when many of the tasks involving solvents such as trichloroethylene (TCE) and trichloroethane (TCA) were performed manually. These improvements have helped ensure that workers’ exposures to chemicals have been substantially reduced in the automated factories of today. Grossman further points out that the groundwater at current Superfund sites is now contaminated with TCE and TCA as a result of leaks and spills that occurred in the early days of the electronics industry. The fact that several residential areas once drew drinking water from these sites and that vapors may pass upward from soil to air has, says Grossman, affected thousands of people. In her review of the available literature on polybrominated diphenyl ethers (PBDEs), Grossman discusses the likely link between human exposure to PBDEs and the high levels of PBDEs in residential dust. Unfortunately, Grossman frequently uses the generic term “PBDEs” rather than specifying which congeners are present in the technical-grade preparation of the PBDEs she discusses. Primarily, technical-grade octabromodiphenyl ether (octaBDE) and decabromodiphenyl ether (decaBDE) are used in the plastic housings of electronics, whereas technical-grade pentabromodiphenyl ether (pentaBDE) is used primarily in polyurethane to manufacture foam and padding materials. The congeners present in the pentaBDE mixture have been shown to accumulate in biological tissues, but the PBDEs in octaBDE and decaBDE have much shorter half-lives in people and are unlikely to biomagnify, although they are detectable in many human tissues. The chapters on recycling and on the flow of electronic waste from consumers to landfills and the export of waste to developing countries are well written and detailed. For example, Grossman states that the United States discards enough electronic waste annually to cover a football field a mile high and that of this waste, only 10% is recycled for materials recovery. Most of the waste goes to landfills or to waste incinerators. Grossman describes the handling of electronic waste that is exported from developed countries into developing countries and the tremendous environmental impact this waste has had in certain countries. For example, in Taizhou in southern China, circuit boards containing lead, flame retardants, and plasticizers are melted for the recovery of metals in uncovered pans only steps away from the workers’ dormitories. In addition, the author offers an interesting description of the different recycling processes used by industrial companies such as Boliden Mineral AB in Sweden and Noranda in the United States. These companies have discovered a “rich ore stream” in the circuit boards they “mine” for metals. Clearly, the increasing tide of electronic waste will be brought under control only if all parties involved (manufacturers, legislators, consumers, and recyclers) implement improvements such as reducing the amount of hazardous materials used in the manufacture of electronic products, producing electronics that are easier to disassemble for recycling, enacting legislation governing the electronics and recycling industries, and ensuring that consumers are informed about the issues associated with the production of electronics and with electronic waste so they can make educated decisions about the issues. Unfortunately, we have just now begun to address these issues, and changes will not be quick or easy.

The use of impact plates in conveyor transfers

In the design of conveyor transfer stations for handling hard-rock mining products wear is one of the major factors that must be addressed. In a general discussion on the design of transfer stations for functionality, ease of maintenance and maximum life, the use and performance of impact plates are discussed. The necessity of keeping a small angle of impact between the ore stream and the plate is highlighted. Limited results from trials on the performance and wear resistance of hard-faced curved impact plates at a copper mine are presented. The mine is handling ore at rates in excess of 40 000 tonnes per day and had suffered from excessive transfer station wear and poor conveyor performance due to problems within the transfers. These problems had been exacerbated with the ore ranging over a wide range of moisture content to saturation and possible clay content to 15%.

Correlation between the contents of a useful component in the ore stream and its influence on the results of extraced ore testing and sorting

Studies involving large-portion testing and large-portion sorting of excavated ores of radioactive, rare, and nonferrous metals by radiometric and nuclear physical methods have been carried out during mining, materials handing, and processing operations in order to determine the source of substantial discrepancies between the calculated and experimental large-portion testing errors and the complex relationship between the yield of tails in large-portion sorting and the principle factors.