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By Liaqat Ali Shah, Muhammad Farooq, Zait Ullah Shah, Francisco Rolando Valenzuela-Díaz

Bentonite collected from Nowshera (Pakistan) was treated with NaCl, and the < 2-μm clay fractions were separated by sedimentation process. The textural changes in NaCl treated purified bentonite were compared with raw and physically purified sample. It was detected that the NaCl-treated purified bentonite and the sample purified by simple sedimentation, respectively, consist of sodium-montmorillonite and calcium-montmorillonite as a major clay mineral. The honeycombed-type morphology was observed for both the purified samples; however, the particles of NaCl treated purified bentonite were relatively in a compact form. The particle sizes of both the purified samples were found considerably smaller. The high volume percent of the fine particles was noticed in the NaCl-treated purified bentonite. This attributed that the sodium exchange has a valuable impact on the bentonite dispersion in aqueous media during particle size measurement. The relatively high mesopore area/volume and micropore area/volume and specific surface area (SSA) were detected in purified samples. The NaCl-treated purified sample showed relatively high mesopores area/volume than the sample obtained by simple sedimentation. These changes seem to be originated from either high montmorillonite contents and/or the smaller particle size, which might be produced after the layer rearrangement during the interlayer cation replacement by Na+ ions. The large SSA and high porosity of purified samples particularly the NaCl-treated bentonite suggest their potential use as adsorbents, catalysts, pharmaceuticals, and cosmetics.

Jan 7, 2021

By S. Michael, T. E. Moongo

Electrowinning consumes a substantial amount of electrical energy, and owing to the ever-increasing unit cost of electrical power there is a need to improve current efficiency in the process. This research was carried out to design a continuous quality improvement framework for improving electrowinning current efficiency by applying statistical process control (SPC) on an online industrial copper electrowinning operation. A sequential mixed research methodology was applied and a statistical software package utilized for analysing data. It was concluded that metallurgical short-circuits (hotspots) had the most significant effect on current efficiency. Bringing hotspots under statistical control resulted in a 5.40% improvement in current efficiency, which is equivalent to approximately 74 t of 99.999% pure grade A copper cathode production over a period of 1.5 months.

Jan 1, 2021

By André Vela

Este trabajo técnico describe el desarrollo de un sistema de alineamiento láser en un equipo Raptor 55-2R de la marca Resemin —utilizado en minería subterránea— con el objetivo de mejorar la precisión y eficiencia de los procesos de voladura mediante el monitoreo de los grados de libertad del equipo de perforación. La solución encontrada aplica métodos algebraicos y un algoritmo de robótica (Denavit-Hartemberg) para describir la cinemática del brazo El estudio incluye pruebas de simulación.

Dec 31, 2020

By IPMI Educational and Scientific Foundation

It is with great pleasure that we announce the availability of this fourth issue of the IPMI Journal, a publication of the International Precious Metals Educational and Scientific Foundation. This digital peer reviewed publication has been created as a vehicle for the sharing of technical information related to the science and technology of precious metals. Since 1976, the International Precious Metals Institute has championed the exchange of information of critical importance to the precious metals scientific and commercial communities through its various communications vehicles. This has included instructional videos, annual conference symposia, special topic committee meetings, regional seminars, and professional and student achievement awards. Due to the breadth of important topics related to all aspects of precious metals, it has been the vision of the IPMI to provide a publication available to the general public that would become a key source of pertinent topics containing high quality publications by experts in their fields of study. Historically, the IPMI has attracted world renowned experts in many fields (including Nobel Laureates Henry Taube, Ei-ishi Negishi, Robert Grubs, Professor Ben Feringa, and David MacMillan) in the dissemination of discoveries, inventions, and industry proven practices. Such information has a total value greater than the sum of its parts as seemingly unrelated innovations from distinct focus areas can be adapted to solve problems. Because of this important characteristic of information exchange, we have decided to create a digital journal, available to the general public, that will not only communicate state of the art discoveries and sound practices, but will also review historical communications from the IPMI’s archives that have value and use even in today’s environment. On behalf of the members and leaders of the IPMI, we hope you will find value in this new publication.

Dec 1, 2020

By Basak Anameric

This study reports preliminary feasibility investigations for utilization of the selective carbothermic reduction and smelting (SCRS) processing scheme to beneficiate low-grade iron-manganese (Fe-Mn) mineral deposits from MN, USA. The study includes laboratory-scale demonstrations using an induction furnace and production of various products by manipulation of operational parameters. The products include alternative iron (Alt Fe), high carbon ferromanganese (HC FeMn), alternative silicomanganese (Alt SiMn), and upgraded manganese concentrate (Mn conc). All of these products have commercial value and can be used in various applications as raw materials.

Nov 23, 2020

By C. Webb, M. A. Tuck

This paper describes the application of a cable disc elevator to continuous lift ore vertically from underground mines. Application of this system requires the tensions developed within the cable must remain within the carrying capacity of the cable including applicable safety margins. A critical element occurs at starting the system when it is fully loaded which requires the force developed by the system to exceed the static friction forces. This paper describes the laboratory rig developed to investigate the static friction forces. Details of the results of tests on three different ores for both dry and wet conditions are given. These results are discussed.

Nov 19, 2020

By Hemant Agrawal, Arvind Kumar Mishra

Rock breakage using blasting is one of the important operations of the mining industry. The delay timing decides the initiation sequence of holes in the blasts and is a crucial factor to improve the overall blast performance. Blast-induced ground vibration is an undesired yet unavoidable outcome of blasting. Peak particle velocity (PPV) is commonly used to measure the magnitude of blast-induced ground vibration. Channelization and better utilization of explosive energy delay are provided between blast holes using initiating systems. The use of different initiation systems even on the same site results in a very significant difference in the values of PPV generated. Due to scattered delay timings of pyrotechnic detonators, the scaled distance predictor equations obtained become unreliable. The error/scatter in delay timing leads to overlapping of holes and hence increases in maximum charge per delay. In this paper, an analytical approach has been discussed to measure the overlapping of holes during blasting with initiation systems having inherent cap scatter. The analytical approach will be calculating the probable overlapping of holes due to scatter in delay timing and will help blasting engineers to understand the variation in maximum charge per delay due to pyrotechnic based initiating systems. In this study, a total number of 102 blasts were conducted using different initiation systems at two different opencast coal mine and 221 corresponding blast vibrations events were recorded.

Nov 10, 2020

By N Clarke, J Hunt, A Barros, L Keeney

The Gramalote orebody is a large low-grade gold deposit situated in the San Roque municipality, 124 km north-east of Medellin in Antioquia, Colombia. It is jointly owned by AngloGold Ashanti (AGA) and B2Gold and is currently in Feasibility Study phase. In 2013 AGA requested CRCORE to undertake a preliminary study of the potential application at Gramalote of pre-concentration by screening, part of the Grade Engineering suite. 160 samples of coarse assay rejects (-3 mm) were tested and showed one of the strongest responses seen worldwide to that time, suggesting that about 70% of the gold could be recovered into 40% of the mass. This was seen as potentially markedly improving the Gramalote economics. A large-scale testing program was implemented on site to follow up these results. A total of 18 samples of 17 t each were mined along a pre-existing exploration adit. A complex test flowsheet allowed size fractions to be generated from the as-received material as well as after crushing to 53, 23 and 3 mm, all from the same head sample. The procedures were designed after carrying out a heterogeneity study to measure sampling errors. The coarser size fractions were designed to study the effect of crushing on upgrade response and predict the response on open-pit run-of-mine ore. The finer size fractions were designed to investigate means of predicting the upgrade response across the orebody. The large-scale testing closely confirmed the average upgrade response as predicted from drill core assay rejects but found that only the -53 mm crushed material accurately predicted the upgrade response of individual samples. Ore geochemistry was able to usefully distinguish samples with good and poor response. A small study on drill core suggested that, for Gramalote, fine crushed material distinguishes vein associated and disseminated values but not other factors that control actual outcomes.

Nov 10, 2020

By C Beal, S Singh

Sensor-based bulk ore sorting is a form of preconcentration that autonomously measures and physically separates discrete bulk ‘pods’ of run of mine (‘ROM’) or primary crushed material. This case study examines the results of a full scale bulk ore sorting trial undertaken at Cozamin mine in Zacatecas, Mexico in 2019. The bulk ore sorting plant comprised primarily of a mobile jaw crusher, fixed conveyor, MR analyser, and diverter gate. Results of the trial demonstrate that bulk ore sorting could deliver a net improvement in copper metal fed to the processing plant of 6-8 per cent within an equal gross tonnage of ore. Copper metal increases were the result of improvements in mining recovery, where valuable mineralisation is recovered from marginal or sub-grade material that would otherwise be discarded as waste or stockpiled as low-grade. The increase in mining recovery more than compensates for metal losses suffered in the bulk ore sorting plant.

Nov 10, 2020

By J Zhou, T D. McGrath, K P. Galvin, C P. Lowes, J J. Eksteen

Pre-concentration of low grade ores can improve the economic and environmental sustainability of an operation significantly, with opportunities for implementation ranging from run-of-mine to mill discharge depending on ore specific characteristics. For a gravity separation, where the performance is fundamentally constrained by mineral liberation, these feeds often represent a very difficult separation given the dominance of the relatively coarse gangue and fine liberation sizes. Thus, building knowledge of the feed through characterisation of the density distribution is critical to assessing amenability before progressing towards lab/pilot-scale test work and full-scale operation. The traditional approach to determining the density distribution typically involved sink/float testing, however, recent developments in hydrodynamic fractionation using inclined channels now offers a more cost-effective alternative with minimal health and environmental risk. A non-hazardous dense liquid, namely an aqueous solution of lithium heteropolytungstates (LST), is supplied as fluidisation to a REFLUXTM Classifier, consisting of a vertical section below a system of inclined channels, operating in semi-batch configuration. Fractionation is achieved by increasing the flow rate incrementally and collecting the particles to form a series of flow fractions. The purpose of this paper is to present this new method in the form of a case study, aimed at assessing the amenability of a low grade gold-bearing sulfide ore to pre-concentration. The robustness in the method is demonstrated through comparison with sink/float data, examining the density distribution and the liberation-limited product grade and recovery achievable. These data are then used as a benchmark to assess water-based continuous gravity separations conducted on the feed using a laboratory-scale REFLUXTM Classifier. This data set is used as the basis for process modelling and empirical validation for the recently established partition surface of the separator.

Nov 10, 2020

By V Chamberlain, M Appeah Owusu, M Aniawu-Asumakah, A Anyimadu, R Peattie

This is an integrated geology and plant improvement study arising from the heterogeneity seen in mineralogy and gold association at the Obuasi goldmine in Ghana. This heterogeneity comes from the two ore types mined, the one being a sulphide ore, mainly composed of gold-bearing arsenopyrites. This gold is refractory and exhibits a strong relationship between gold and As. The other is quartz veins, that are high grade and free milling. The installed circuit consists of comminution – Gravity -Flotation – BIOX – Leaching and Adsorption processes. The opportunity tested involved improved mass pull - related flotation recovery of Au in the Sulphide stream; while balancing the need for a minimum Sulphide grade for the Bio-oxidation process, occasioned by the removal of 25 to 30 % of the (quartz) stream through preconcentration by Ore sorting. The current circuit is then utilized for the sulphide route, while a smaller grind-gravity circuit is utilised for the quartz stream in a relatively inexpensive way, followed by a common leaching and adsorption circuit. Added advantages of the strategy includes faster recovery of gold from the quartz stream, with less consumption of reagents from saving on flotation and BIOX reagents for this stream. Screening and Ore sorting was successfully tested with laser technology, achieving over 98% separation of quarts (containing up to 40% of the gold). The plant schedule of Ore, the suggested circuit design for the Ore sorting, the results obtained from the different flotation regimes, as well as consequent financial modelling have been presented and discussed in this paper. This illustrates the opportunity that arises out of a detailed analysis of material versus installed circuits, even if the gains in pre-concentration do not necessarily involve rejection of gangue material. An added opportunity for future investigation, briefly discussed but not tested in this paper, would be to maintain current mass pulls but with increase in throughput (by the space created by the sorted material). This will of course require the mining ability. It could also add LOM value by altering the cut-off grade.

Nov 10, 2020

By D Gagnon, P Bouchard, F Vanier, E Soares de Lima Filho, J El-Haddad, M Sabsabi, G J. Wilkie, A Beauchesne, A Hamel, A Blouin, T Vaillancourt, F Boismenu, A Harhira, A Plugatyr, C Padioleau

Quantitative mineralogy is an established discipline in the geosciences and is aimed at providing mineral grade and texture information for geological and mineral processing applications. The two core technologies underpinning Quantitative Mineralogical Analysis (QMA) are Scanning Electron Microscopy (SEM) in combination with Energy-dispersive X-ray Spectroscopy (EDS). Technologies such as QEMSCAN and MLA are now routinely used to optimise the performance of large-scale mineral processing plants in the base and precious metal sectors. One of the major disadvantages of the QMA methods used today is extensive sample preparation requirements which make application of this technique to real-time mineralogical characterization not feasible. A breakthrough has been achieved by the National Research Council Canada in collaboration with CRC ORE by developing a novel Laser Induced Breakdown Spectroscopy (LIBS) based technology capable of real-time mineralogical characterization of process streams without sample preparation. The potential applications of this technology include, but not limited to, in-pit muck piles, underground draw points, cross-belt analysis as well as slurries. This paper describes the development of the LIBS-based technology from a proof-of-concept (TRL2) to the construction of a prototype sensor and its validation in a simulated environment (TRL5). Future work is being planned to test and further validate the LIBS sensor on a mine-site which will progress the technology to its next readiness level (TRL6).

Nov 10, 2020

By J Rutter, D Francois-Bongarcon, M Federov, N Odiar, M Scott

There are two fundamental methods for metalliferous sensing of primary crushed ore available for deployment at operations. These methods can be classed as surface measurement techniques (including XRF, LIBS, NIR, SWIR) or penetrative/semi-penetrative measurement techniques (including PGNAA, PFTNA, GAA, MR). While the individual sensing technologies exploit different physical phenomena to measure metal content, penetrative sensor measurements of grade are often regarded to be superior to surface measurement techniques due to the much larger sampling volume penetrative techniques provide. Surface sensing techniques often utilise simpler, established technologies that have considerable benefits in the speed of analysis, capital costs, ease of deployment, social license to operate and operational safety. This paper investigates whether surface sensing techniques achieve adequate sampling representativity of primary crushed rock mass to provide economic benefit over penetrative sensing technologies for bulk ore sorting applications. The paper details the methodology used to assess whether surface XRF measurements change throughout various stages of comminution, and increased surface exposure, from primary crushed ore (top size of -175mm) to finely crushed product for assay (top size -2mm). The methodology was applied to 2 ore mineralisation styles, across variable metals and grades, to identify any associated opportunities and limitations to surface sensing techniques. The results assist in developing a method to determine if surface sensing and measuring via XRF is an adequate representation of the rock mass for bulk ore sorting applications and identify any associated limitations in particle size distribution, mineralisation or natural deportment strength to guide suitable application of surface sensing techniques.

Nov 10, 2020

By M Pyle, R Ch, T Vizcarra, ramohan, G Lane, G Ballantyne

Preconcentration, through gravity separation (Wallace et al, 2015), magnetic separation and particle size (Clout, 2013), has been used in many historical projects to convert low grade material into ore. More recently, pre-concentration technologies such as bulk sorting (Kurth, 2017), screening (Bearman, 2014) and coarse particle flotation (Vollert et al, 2019) have also demonstrated their ability to progressively reject waste through the value chain. These technologies can not only deliver stepchange improvements to the economics of mining operations, but can transform the environmental and social aspects by minimising water and energy consumption and significantly reduce the quantity of fine tailings produced. However, implementing progressive waste rejection requires technologies and approaches to be combined and applied in the right way to capture the value. From a technical perspective, progressive waste rejection introduces challenges related to the orebody, equipment performance, engineering and understanding the value chain from the resource through to final product. From a management perspective, the key issues are related to people and processes, in particular; motivating the business, challenging the paradigms, and introducing new ways of operating within the constraint of existing management structures to manage risks and minimise lost opportunity costs. This combination of technical and management issues means that progressive waste rejection is a complex undertaking for mining companies, yet the reward for the business and other stakeholders is potentially high and should not be ignored. This paper presents how progressive waste rejection can offer step-change improvements to the business case for high and low grade greenfield and brownfield projects based on case studies completed by Ausenco. The paper then outlines different implementation approaches from concept studies to execution to address the various technical and management challenges outlined above.

Nov 10, 2020

By R Yong, A McEwan, D G. Miljak, D Milinkovic, A Curtain, P J. Coghill, R Stefulj, B Lovric, G Roberts

The CSIRO has pioneered the development and use of certain classes of magnetic resonance (MR) for mining applications. The MR technique is a radio frequency-based spectroscopy that provides highly quantitative measurement of selected ore minerals. MR has many inherent advantages for bulk sensing in mining applications, including deep sensing penetration into most bulk ores with the use of non-contact sensors that are robust and tolerant of demanding mine conditions. The highly discriminating nature of the technique also provides the very desirable attribute of robust and simple calibration, that can often be performed prior to sensor installation. Rapid sensing (within seconds) at very low grade (few hundred ppm Cu) has been demonstrated, as well as sensing at high tonnage rate. Besides sorting applications, MR may also be applied to preconcentration applications involving very large volume sensing including: (i) haul truck sensing using portal arrangements, where truck destination assignment may be dynamically determined based on the truck grade, (ii) in-pit gantries used for loading trucks that may similarly be equipped with sensors for truck assignment and (iii) deep mine bench sensing, recently progressed through a CRC ORE project, where local bench grade is determined at the few-metre lateral scale and at depth prior to blasting, to aid selective blasting and ore extraction. MR sensor prototypes have been developed for each of these applications and have been tested in laboratory or limited field conditions. To inform the value proposition for truck or bench sensing, initial analysis of truck assignment improvement based on an analysis of in-situ mine bench grade has been performed for a porphyry style deposit. The prototype sensors, preliminary results and future technology development and objectives will be described.

Nov 10, 2020

By T BoBo, D La Rosa, P Cameron

Efficient pre-concentration using natural and induced deportment starts with effective blast design. Leveraging these characteristics using Size-Based Grade Engineering® techniques requires detailed understanding and measurement of the particle size distribution (PSD) of the Run of Mine (ROM) ore. In turn, blasts must be designed to optimise fragmentation for the pre-concentration method. To be successful, fragmentation outcomes must be predicted and measured as part of the blast design process to account for the response ranking of the rock mass. The upgrade achieved using Size-Based Grade Engineering® methodologies will rely on the proportion of feed that reports to the screen undersize, so particle size distribution of the feed stock is of paramount importance if the potential benefits are to be achieved and maintained. Measuring actual fragmentation in the ROM ore and comparing with predictions allows the modification of subsequent blast designs to optimise fragmentation for pre-concentration scenarios. Automating this process can deliver significant increases in productivity and mine site profits. This paper discusses the importance fragmentation plays in Size-Based Grade Engineering® and explores technologies and methodologies used to measure it, consistently ensuring the best outcomes.

Nov 10, 2020

By Y V. Haarlem, P Coghill, N G. Cutmore, M Millen, I Carter

Due to the low concentration of gold, ore sorting for gold has always required measuring indirect properties, such as density or colour, to allow separation on a rock by rock basis. This only works on an ad hoc, by deposit basis and is likely to be least reliable where it is most required in low grade ores. One candidate technique, Gamma Activation Analysis (GAA) has been demonstrated to directly measure gold extremely accurately in powder samples of around 500gm and is used in the Chrysos PhotonAssay assay system. This method uses a linear accelerator (linac) to generate the X-ray radiation that activates the ore at low levels to emit a characteristic gold gamma ray that is then measured by a radiation detector. CSIRO is adapting this measurement technique to application on a belt at up to 800tph to measure pods of ore. The principal differences between measuring samples and an on-line measurement of pods are the requirement to measure coarse ore (<50mm), to measure a larger volume of ore as uniformly as possible, and to have an open-ended geometry with adequate shielding of the linac radiation source. These issues have all been addressed with measurements of coarse ore reported down to around 1ppm in sub-optimal test conditions. They have been demonstrated for <75mm particles with detectors capable of measuring a large volume geometry continuously. These are projected to allow measurements down to 0.3ppm in more optimum conditions for a 10 second measurement time period where the U/Th content of the ore is less than ~10ppm. Extensive Monte Carlo modelling has demonstrated that adequate shielding can be provided in relatively simple geometries with only 1 right angle transfer in the material handling. Steady progress is being made to reach the technical position required to trial an ore sorting system.

Nov 10, 2020

By Liming Yuan, Isaac Zlochower, RICHARD THOMAS, Thomas H. Dubaniewicz, Teresa Barone

Mining vehicle manufacturers are developing lithium-ion (Li-ion) battery electric vehicles as an alternative to diesel-powered vehicles. In gassy underground mines, explosion-proof (XP) enclosures are commonly used to enclose electrical ignition sources to prevent propagation of an internal methane (CH4) air explosion to a surrounding explosive atmosphere. Li-ion batteries can create pressurized explosions within sealed enclosures due to thermal runaway (TR). Researchers at the National Institute for Occupational Safety and Health (NIOSH) measured TR pressures of lithiumiron phosphate (LFP) cells as a function of free space within sealed enclosures and observed an inverse power relationship. A well-confined cell produced 294 bar (4260 psia) of pressure during a TR, far exceeding minimum pressure containment specifications for conventional XP enclosures. Results indicate that adding enough free space surrounding LFP cells can reduce TR pressures to levels below that expected for CH4-air ignitions. Measured TR temperatures were below the minimum autoignition temperature of CH4-air.

Nov 6, 2020

By John Rajala

The Otjikoto Gold Mine in the Republic of Namibia is located approximately 300 kilometers north of the capital city of Windhoek. The project features surface mining with a modern gravity/carbon-in-pulp mill for ore treatment and recovery of gold. Initial mill design capacity was 2.5 million tonne per annum but then expanded after 9 months of operation to 3.1 million tonne per annum. The technical steps to establish the Otjikoto mill design from process selection in the due diligence stage, through flowsheet development in the feasibility study followed by detailed engineering design are reviewed in this paper along with mill performance during start-up and in 2019.

Oct 30, 2020

By Umay Cinarli, Ahmet Turan

High-energy consumption in primary aluminum production (from bauxite ores) makes secondary aluminum production (from metallic raw materials such as scrap and dross) very critical. Aluminum dross, as a waste, arises in pyrometallurgical processes, and it is the mixture of metallic Al, Al2O3, other metal oxides, metal halides, and some other compounds like AlN. Aluminum dross has two subgroups (white and black) with respect to its metallic aluminum content. White dross is a secondary aluminum resource because of its high metallic aluminum content, whereas black dross, having low metallic aluminum content, is generally disposed in dumping areas. In the present study, it was aimed to develop a simple technique to valorize aluminum black dross in the form of alumina-based ceramic materials through pyrometallurgical (calcination) and hydrometallurgical (leaching) operations. Moreover, thermochemical simulations were conducted by using HSC Chemistry 6.12 software to simulate calcination conditions. After leaching experiments, an alumina-based ceramic containing approximately 36.8% Al2O3, 61.4% MgAl2O4 with 1.8% Na2FeO4, which might be available to use as a spinel refractory in steel smelting furnaces, was obtained in the experiment carried out in a solution containing 10 mLH2SO4 and 40 mL distilled water (3.5 M). Moreover, the sinterability of the alumina-based ceramic was investigated at the temperatures from 1350 to 1550 °C. In the sample which was sintered at 1550 °C, a density value of 3.15 g cm−3 and a hardness value of 69.58 HV were measured.

Oct 26, 2020