Search Documents

By F. S. Beretta

Mineral processing efficiency depends on various factors and among them includes head grade fluctuations feeding the processing plant. Head grades can fluctuate beyond an admissible range, implying in recovery decrease for the mineral of interest. Grades feeding the processing plant depend on the geological domain which is being mined and on the mining schedule. Therefore, it is necessary to keep grade variability controlled. Blending piles are an efficient alternative to reduce grade fluctuations. The main factors influencing blending efficiency are the pile size or its mass and the number of layers used to pile up. Large piles are more efficient to reduce variability, however, there are economical and operational limits associated with them. This study investigates a methodology to analyse the ideal pile size to reach an acceptable variability given the in situ grade fluctuations. Geostatistical simulations provide the means to assess grade variability using an optimized mining schedule. These block grades are used to simulate any given pile throughout the mine`s life. The methodology was illustrated using a case study to control coal ash content at a mine supplying ROM coal to a power plant. Keywords: homogenization, piles, geostatistical simulation.

Jan 1, 2009

By J. A. Batista-Rodríguez, F. J. López-Saucedo

A new methodology is proposed for the preliminary assessment of coal blend quality, which combines gamma-ray spectrometry and magnetic susceptibility measurements. This methodology does not replacethe conventional methods of assessing coal quality, but can help to control the quality of the coal blending process, as well as reduce the amount of proximate analysis required and the determinations of calorific value and total sulphur. The methodology includes five steps. First, both geophysical measurements aremade with handheld equipment. The samples with magnetic susceptibility ≤ 1 × 10-3 SI are then separated. From these samples, those with total gamma intensity ≤ 20 nGy/h are separated. These samples have a higher calorific value and lower ash and moisture content. To separate the samples of better quality and with lower total sulphur content, in step four the samples with total gamma intensity > 20 nGy/h are separated from those with magnetic susceptibility ≤ 1 × 10-3 SI. This last group includes samplesthat will cause less total sulphur-related environmental pollution. In the final step, the quality of both radioactive sample groups is corroborated from the calorific value measurement and ash, moisture, andtotal sulphur contents in at least 10% of all coal blend samples from both groups. In this study, more than1000 samples were analysed with this new methodology, and the results are remarkably similar to the ASTM classification of the Sabinas Basin coals.

Apr 2, 2022

By D. Weijie, S. Kai, Y. Hu, X. Ning, M. Shiyi, W. Junpeng, Z. Guihong, L. Xianjie

Flotation is one of the most important processes in the copper production industry. The copper grade in the concentrate is a pivotal indicator of the flotation process performance. However, it is difficult to achieve real-time measurement through hardware sensors. Based on the production data provided by an industrial operation, a novel soft sensor based on multi-layer perceptron (MLP) is proposed for effective monitoring of this pivotal indicator. The proposed soft sensor uses the nonnegative garrote (NNG) to perform global variable selection for MLP, while a local search (LS) approach is incorporated to improve the model presented by NNG. Simulation results show that the proposed algorithm has higher prediction accuracy and better model simplicity than other algorithms. Furthermore, the variables selected are consistent with the field experience, and the developed model can provide reference of feedback control for the optimisation of the process. Keywords: Flotation process of copper ore, nonnegative garrote, local search, soft sensor, multi-layer perceptron

Jan 1, 2020

By J. A. Sweet, T. BACHMANN, G. E. Sandoval, T. M. Hauyon, F. A. Contreras

In many respects a porphyry copper ore concentrator plant can be considered as a simple system. Chalcopyrite typically liberates well at relatively coarse sizes, and even low grade ores are amenable to upgrading 20 to 30 times to produce concentrate grades in excess of 25 % in very simple Rougher- Regrind-Cleaner+Scavenger flotation circuits. The flotation response of chalcopyrite has been well characterised in many fundamental and applied research studies and the conditions necessary to depress pyrite and other floating gangue species are well understood. But what happens to the particle surfaces when you have a 50 km pipeline between the grinding circuit and the flotation plant? How does the seasonal variation in water quality affect your ability to control pulp chemistry? What impact does the relative concentration of the different sulphide species have on their separability? Why do two plants that receive nominally the same ore produce consistently different results? And most importantly, what do you need to do to improve the performance of both plants? To answer these and other questions, a focussed sampling and analysis programme was carried out at the Las Tórtolas flotation plants in 2018 and 2019. The work included full down-the-bank sampling, hot floats, the use of radioactive tracers for determining residence time distribution profiles, gas dispersion measurements, detailed mineralogy by size across the circuits and multiple regrind surveys. This comprehensive study was augmented by analysis of historical mineralogy, geometallurgy and operating data using modern data science techniques, and has provided the foundation for current and future optimisation initiatives. Some of the findings and their implementation will be presented in this paper. Keywords: Circuit optimization, Residence time, Gas dispersion, Pulp chemistry

Jan 1, 2020

By D. N. Golenkov, N. I. Lomaka, A. V. Kozub, T. V. Ignatova, E. V. Shelepov, D. O. Sharkovskiy, A. V. Chanturiya, R. I. Ismagilov

The modern Russian iron ore mining industry is faced with multiple challenges from everincreasing requirements of steel-making, the value of iron ore concentrates, depletion of high-grade ore reserves and complications of the mining and geologic environment’s necessity to process low-grade ores with complex material composition and low valuable mineral content; with finely disseminated aggregates of metal and non-metal minerals responding similarly to processing. The upgrade of the existing operations’ fine wet screening was implemented by Metalloinvest; as well as the design of a process flowsheet for concentration oxide ferruginous quartzites with low concentrating ability. The scientific basis for improvement of low grade ore concentrating efficiency and the upgrade of market product quality is supported by an in-depth study of ore characteristics, application of high performance equipment for separation of fine-grained mineral aggregates and use of depressor selective to ferruginous minerals in the flotation process. The benefits of wet fine screening have been proven by industrial scale tests; as well as the feasibility of significant upgrades in product quality which have been confirmed as a result of the tests. A road-map for the upgrade of an existing process for the concentration of unoxidised ferruginous quartzites deposited in the Mikhailovskoye ore field was developed, based on the industrial scale test of a fine screening process. With reference to the ability for concentration, three major ore types oxidised ferruginous quartzites were defined as a result of comprehensive geological mapping and process sampling: oxidised ferruginous quartzites with good concentrating ability: over Fe67% grade of concentrate with ca. 80% iron recovery; oxidised ferruginous quartzites with moderate concentrating ability: Fe65-67% grade of concentrate with 70-72% iron recovery oxidised ferruginous quartzites with low concentrating ability: below Fe60% grade of concentrate (cannot be processed into desired grade market product). A process flow diagram combining magnetic separation and flotation has been designed and recommended for implementation based on the in-depth research of defined Mikhailovskoye deposit iron oxide types, including grain size, chemistry, petrographic, mineralogy, hematite and magnetite grain size distribution and liberation analysis.

Jan 1, 2020

By A. Mabentsela

A furnace freeze lining is necessary for safety and economic reasons in several smelting operations. The integrity of the freeze lining is put at risk by furnace power imbalances. Although numerous models have been derived to model the growth and depletion of the freeze lining due to power imbalances, no model exists for thermomechanical damage to the freeze lining. This study provides an initial pathway for modelling thermomechanical damage to the freeze lining in an ilmenite smelting furnace using information from the literature and experimental work. A methodology under the framework of continuum damage mechanics is proposed to model mechanical damage to the freeze lining due to phase changes, thermophysical changes, and constrained thermal expansion. Drill cores of solidified slag ingots were used to represent the freeze lining. The modified power law proved to be the best predictor of the softening response of the drill cores. Damage driving parameters were extracted from the raw data, and governing equations of the parameters with respect to temperature were derived for use in a finite element method (FEM) code.

Jan 26, 2023

By S. Combrink, N. Naude

Hydrocyclones are widely used in wet mineral classification applications and can be notoriously prone to wear. The methods currently used for quantifying hydrocyclone wear profiles are mostly twodimensional. In this paper it was attempted to quantify and monitor wear in three-dimensions, using a micro-CT scanner (Nikon XTH 225 ST). Hydrocyclone wear and, more specifically, spigot wear was investigated on a Multotec HC250 (Dc 250 mm, barrel diameter) hydrocyclone. The hydrocyclone is lined by a vulcanised natural rubber compound within a metal shell, with a thermosetting polyurethane spigot and vortex finder. Tests were conducted on the hydrocyclone in a pilot-scale recirculating test setup. The wear rate of the spigot was quantified by measuring the volume change within the spigot over 122 days in operation, using the micro-CT scanner. After 122 days in operation (recirculating feed materials) the wear in the hydrocyclone led to only a 13.67% loss of spigot volume. The relatively low wear rate could be related to the fact that material recirculation led to particle smoothing and a reduction in size, thereby decreasing the wear rate. This also shows the enormous influence that particle shape and size have on wear. The research was conducted with the support of Multotec, NECSA and the University of Pretoria. Keywords: Wear, hydrocyclone, micro-CT

Jan 1, 2020

By M. Ye. Scheglov, G. I. Voiloshnikov, S. M. Ryakhovsky, V. E. Dementyev, V. N. Alekseev, N. S. Voiloshnikova

Irgiredmet has substantial experience on RIP and RIL technology for gold recovery, having started development of ion exchange technology in 1964. Irgiredmet specialists were involved in the majority of RIL and RIP projects in the former Soviet Union and Russia, and took part in commissioning of practically all plants using ion exchange technology. Laboratory and pilot plant tests were conducted to develop process design criteria for designing 15 RIP plants of the former USSR using bifunctional macroporous anionite AM-2B or its analogs. This paper is devoted to the laboratory, pilot plant testing and introduction of RIP technology conducted in cooperation with GC Pertopavlovsk. Medium base resin PuroLite S992 (PuroGold) was used as adsorbent. Some adsorption regularities and the affinity of resin to metal cyanide complexes were studied. Laboratory batch and continuous pilot tests on resin-in-pulp process were held for oxidised ores from Pioneer, Albyn and Malomyr mines (Amur region, Russia) owned by the Petropavlovsk company. A simplified flowsheet for gold elution and resin regeneration was developed. Alkaline cyanide solution was used as gold eluent and gold was recovered from eluates by electrowinning. Process design criteria were developed on the basis of the testwork results, and the plants were designed and constructed by GC Petropavlovsk. The RIP plant at Pioneer was commissioned in May 2008, at Malomyr in August 2010, and at Albyn deposit in December 2011. These plants are currently in operation at design performance at throughputs from 3 to 6.5 Mt/year. The primary gold ores of Pioneer and Malomyr deposits are refractory to cyanidation; Irgiredmet also completed continuous testwork on RIP technology using medium-base resin for pressure oxidation (POX) residues derived from their flotation concentrates. In 2019 a hydrometallurgical plant for the treatment of refractory gold concentrate after POX was commissioned at Pokrovsky mine (Amur region). Keywords: Gold ores, cyanidation, RIP, RIL –processes, ion exchange resin, medium base resin, adsorption, elution, electrowinning

Jan 1, 2020

By J. L. Havenga, L. J. van der Walt, J. T. Nel, H. Bissett

"SynopsisNew technologies used to manufacture high-quality components, such as direct laser sintering, require spherical powders of a narrow particle size distribution as this affects the packing density and sintering mechanism. The powder also has to be chemically pure as impurities such as H, O, C, N, and S causes brittleness, influence metal properties such as tensile strength, hardness, and ductility, and also increase surface tension during processing.Two new metal powder processes have been developed over the past few years. Necsa produces zirconium powders via a plasma process for use in the nuclear industry, and the CSIR produces titanium particles for use in the aerospace industry.Spheroidization and densification of these metal powders require remelting of irregular shaped particles at high temperature and solidifying the resulting droplets by rapid quenching. Spherical metal powders can be obtained by various energy-intensive methods such as atomization of molten metal at high temperatures or rotating electrode methods. Rapid heating and cooling, which prevents contamination of the powder by impurities, is, however, difficult when using these methods for highmelting- point metals. For this reason plasma methods should be considered.Thermal plasmas, characterized by their extremely high temperatures (3000–10 000 K) and rapid heating and cooling rates (approx. 106 K/s) under oxidizing, reducing, or inert conditions, are suitable for spheroidization of metal powders with relatively high melting points. Thermal plasmas for this purpose can be produced by direct current (DC) plasma arc torches or radio frequency (RF) inductively coupled discharges. In order to obtain chemically pure spheroidized powder, plasma gases such as N2, H2, O2, and CH4 cannot be considered, while Ar, Ne, and He are suitable. Neon is, however, expensive, while helium ionizes easily and it is therefore difficult to obtain a thermal helium plasma at temperatures higher than 3000 K. Therefore argon should be used as plasma gas. Residence times of particles in the plasma region range from 5–20 ms, but this is usually sufficient as 7–8 ms is required for heating and melting of titanium or zirconium metal particles in the 30 µm size range at 3500 K. In this study the melting and spheriodization of titanium powders was investigated by DC non-transferred arc and RF induction plasma methods. The powders were characterized before and after plasma treatment by optical microscopy and scanning electron microscopy (SEM) to observe if any melting or spheroidization had occurred."

Jan 1, 2015

By A. J. H. Newell, K. Doherty

A copper-gold project has required a number of trade-off studies underpinned by test work to settle on pragmatic flowsheets and throughputs to support a pre-feasibility study that provides a compelling financial case. The primary trade-off studies were based on the mine schedule, ore type feed-grade recovery relationships, likely concentrate grades and typical marketing terms as well as the estimated capital and operating costs for a range of throughputs and mining strategies. Secondary trade-off studies were conducted for specific circuits and additional processing options. Although the details of these studies are not presented, the technical options and subsequent flowsheets are discussed. While the flowsheets will be optimised during the feasibility study stage, the basis is now fixed for the four ore types that would be mined from the copper-gold orebody. The ore types, resulting from a strong weathering profile, exhibit a wide range of copper mineralisation and gold associations, as well as gangue types. They display a range of characteristics that necessitated a nuanced approach to flowsheet development. The primary separation techniques that have been employed include gravity, classification, flotation and leaching while a range of comminution methods have been selected to suit the properties of the ore types. While technical issues are important factors in terms of maximising the quality of separations, recoveries and revenues, attention to material handling, equipment characteristics, the mine schedule, and capital and operating costs are equally important considerations for settling upon a suitable and robust flowsheet. Keywords: Flowsheet, testwork, studies, saprolite gold, native copper, chalcocite, chalcopyrite

Jan 1, 2020

By S. Govender, J. J. L. du Plessis, R. C. W. Webber-Youngman

Spontaneous combustion (SC) is a cold oxidation reaction that generates heat, causing a temperature rise of the reactant and leading, with limited heat dissipation, to self-ignition of the reactant, which occurs without an external heat source. Although not limited to coal, the most significant hazard of SC are the fires that occur in coal mining operations around the world. These fires pose a serious risk to the safety of workers in the mines as well as adverse effects on the environment, and can affect the quality of life for current and future generations. We investigated the occurrence of SC in raw coal storage bunkers with the purpose of compiling a decision analyser for engineers designing or working with coal storage bunkers. Specific experts were interviewed from different backgrounds and companies, followed by field research at a coal mine. The important factors affecting the possibility of SC occurring were the type of coal supplied to the bunker, the mining practice, and physical conditions around the bunker. The information presented here will assist in reducing the SC risk in raw coal storage bunkers. These findings, together with the systematic decision analyser developed, will assist design engineers and mine personnel to take early preventative steps in managing SC. The decision analyser was tested for many different scenarios and gave good guidance on how to minimize and prevent SC in bunkers

May 1, 2021

By Xiaoxu Sun, Jianchao Yao, Qiheng Zhu, Dubo Wang, Jiancheng He, Shijie Lu

Tower mill is considered to have a better regrinding and fine grinding effect compared with ball mill, and its application is much broader. The spiral agitator of the tower mill is driven by the motor. Media inside the mill is under the combined actions of the spiral mechanism, the cylinder, and media nearby, and these parameters are key factors affecting the grinding effect. However, it is not possible to obtain detailed information of kinematic law of media based only on traditional laboratory experiments, let alone the relationship between parameters of kinematic law of media and grinding effect. Experimentation is the only way to develop industrial equipment. However, this is time-consuming and costly, which hampers the further research of the tower mill’s grinding mechanism. The paper selects two structural parameters (gap between the edge of the spiral agitator and the cylinder wall, ratio between the diameter of cylinder and that of the spiral shaft.) and three operating parameters (diameter of media, filling ratio, the speed at the edge of the spiral agitator) as variables to do an orthogonal designed experiment of five factors, four levels, and thereby obtaining change law of grinding indicators of different parameters. Experimental equipment may be simplified to enable an applicable simulation strategy. Simulation based on a discrete element method is conducted to obtain the change law of the speed of media, collision frequency, normal force, and radial force. The relational curve between parameters of kinematic law of media and energy consumption of grinding is clarified, and key factors affecting grinding efficiency are determined. Those factors will be used for optimising the design and operating process. The research result of this paper obtained from laboratory experiments and computer simulation provides data support and theoretical bases, and has directive meaning and applicable value for tower mill’s optimisation and large-sized design. Keywords: Tower mill, discrete element method, kinematic law of media, energy consumption of grinding

Jan 1, 2020

By J. Sjöberg, T. Savilahti, S. B. Umar

"Sublevel caving in Malmberget mine results in mining-induced surface deformation. One of the currently mined orebodies is the Printzsköld orebody. As mining deepens there is need to assess the behaviour of the cave formed in the subsurface above this orebody. Numerical analysis was used to assess the effects of extraction to deeper levels and perform strength parametric studies. Stress redistribution was studied, and the results showed high stress buildups in the hangingwall and the crown pillar. Two failure mechanisms have been identified – shear and tensile. Reducing cohesion by 50% increased the area of the yielded zone by more than 100% in the hangingwall.IntroductionThe Malmberget mine is owned and operated by the Luossavaara-Kiirunavaara AB (LKAB) mining company. Iron ore is extracted by large-scale sublevel caving. The mine comprises a total of 20 orebodies, about 10 of which are in production today (Figure 1). The mine is located in the municipality of Gallivare, about 100 km north of the Arctic Circle (Figure 2).Successful sublevel caving requires progressive caving of the orebody after initial blasting. This results in caving of the hangingwall, sometimes all the way to surface, resulting in surface deformation. As mining progresses to deeper levels a larger area is affected by deformation. Over the years, extraction from the Malmberget orebodies has led to deformation of the ground surface, affecting residential areas and existing infrastructure.Forecasting the caving process is not straightforward as it can be rapid or slow, depending on the rock mass conditions, stress conditions, the failure mechanisms at work, etc. Moreover, several of the orebodies in Malmberget are non-daylighting, which makes reliable caving analysis even more difficult, primarily since there is less available experience from such cases. The present study was designed to improve the understanding of the caving and deformation mechanisms at Malmberget, and in particularly for the Printzskold orebody"

Jan 1, 2017

By P. F. Dicks, N. J. Shackleton, E. H. W. Theron, V. Malysiak

Flotation is a complex physical chemical process in which flotation reagents play a vital role in valuable minerals recovery and concentrate grades. This study examines the performance of new generation AECI Mining Chemicals (previously named Senmin) collectors. They were developed to enhance the valuable minerals recovery and flotation selectivity by tailoring the collectors to target specific valuable mineral species present in an ore and thus create added value for concentrators treating PGM ores. The case study was conducted on a Platreef ore, where batch flotation tests were performed and the concentrates were mineralogically characterised for PGE and BMS using QEMSCAN. Further batch flotation testwork was conducted on Merensky and UG2 ores from various localities in South Africa to confirm the trends observed for Platreef ore. The results have shown that there is a strong correlation between PGE mineral type and AECI Mining Chemicals collector type - clearly demonstrating that one reagent type does not fit all flotation applications. Keywords: Batch flotation, QEMSCAN, collectors, PGE and BMS

Jan 1, 2020

By N. Hadebe, A. Mampuru, F. Jantjies

Mintek conducted test work to study the effect of media wear when using Mintek’s Milling-in-raffinate technology. The grinding media consisted of high-chrome and ceramic balls. The tests were conducted using a laboratory 5L 316 stainless-steel rubber-lined mill. Magotteaux supplied the high-chrome and ceramic balls. The raffinate was synthetically prepared using a typical Cu/Co (2.2 g/L Cu, 3 g/L Co) composition. The milling rate, media wear, mill, leach extraction efficiencies, gangue acid consumption, and residence time were studied. The tests indicated that the high-chrome balls had a higher corrosion rate than the ceramic balls. The ceramic corrosion rate was lower than 0.1 mm/y. The highchrome balls performed better during the leach stages with faster milling time, higher leaching efficiencies for both Cu and Co, lower gangue-acid consumption, and lower residence time

Jan 1, 2023

The Annual General Meeting of the Institute was held in Kelvin House, Johannesburg, on Wednesday, 22nd August, 1973. Dr J. P. Hugo (President) was in the Chair. There were also present 64 Fellows, 20 Members, 5 Associates, 3 Students, and 34 Visitors, making a total of 126. The President declared the meeting open at 4.05 p.m. OBITUARIES The President: It is my sad duty to announce the death of the following members of the Institute C. Boocock, R. J. G. Moore, M. P. Pearse, and A. I. Sussman, all Fellows, and W. T. Dalling, a Life Member. As a mark of respect to the memory of the deceased and in sympathy with the bereaved, I ask you to rise and observe a few moments' silence. MINUTES Die President: Item twee op die agenda is die bekragtiging van die notules van die jongste Algemene Vergadering van die Instituut. Daar die notules in die Augustus uitgawe van die Joernaal gepubliseer is, vra ek u toestemming dat dit as sulks bekragtig word. Toestemming verleen. WELCOME TO VISITORS The President: It is my very great pleasure to welcome all the distinguished guests who have honoured us with their presence this afternoon; in particular, a hearty word of welcome to the Honorary President of the Institute, Mr Plumbridge, the President of the Chamber of Mines. You are doubly welcome here, sir, and we thank you for your presence. Also to that old member and stalwart, the Honorary Vice-President of the Institute, Mr Tommy Gibbs, the Government Mining Engineer-you're very welcome, Mr Gibbs. Then, we are particularly privileged this afternoon to have an Honorary Member with us, the Minister of Mines for Rhodesia, Mr Dillon. You will recall that he honoured us with his company last year. Mr Dillon, we are very appreciative and hope that this is now a standing arrangement. We are also honoured by the presence of some thirteen Presidents, Vice-Presidents, or Chairmen of our sister scientific and technical organizations. I shall rapidly read their names, but they must all feel assured that they are very welcome here today. Firstly, one of our own Past Presidents and members, Mr Geoff Goode in his capacity as President of the Associated Scientific and Technical Societies of South Africa; Mr L. R. Robinson, President of the South African Institution of Mechanical Engineers, and Mrs Robinson; Mr G. Goedhals, President of the South African Institute of Electrical Engineers ; Dr Antrobus, President of the Geological Society of South Africa, and Mrs Antrobus; Mr T. V. Dean, Vice-President of the Institute of Land Surveyors of the Transvaal, and Mrs Dean; Mr R. M. Stroh, President of the Mine Ventilation Society of South Africa; Mr Ken Steele, President of the Association of Mine Managers, and Mrs Steele; Mr Mike Gericke, President of the South African Council for Professional Engineers; Mr R. G. Matthews, President of the Institute of Mine Surveyors of South Africa; Mr P. H. Pettifor, President of the Institute of Production Engineers, London, and Mrs Pettifor ; Dr Nico Stutterheim, Chairman of the South African Institute of Chemical Engineers, and Mrs Stutterheim; Professor F. A. van Duuren, Chairman of the Engineers' Liaison Committee in Pretoria; also, I haven't spotted him but I trust he is here-Mr Alex Bain, who is Chairman of this Institute's Witbank/Middelburg Branch. To one and all, ladies and gentlemen, a hearty word of welcome. Not last on our list, a word of welcome to Mr Eric Boden, the Manager of A.S. and T.S. We also have with us I trust, Dr Deist, and his good lady-Dr Deist will be figuring in our proceedings later this afternoon. Also Mr Barcza and Mrs Barcza. Mr Bareza, a former President of the Institute, also has a task to perform. Then, I hope two of our student prize winners are here-Mr Beetge and Mr Painting. Then we also have Mr Roberts, who is welcome in his capacity as co-author with Dr Deist. Then, last of all, a hearty word of welcome to Dr Helen Glen (I am not sure whether she has arrived yet, but she is certainly due to come)-the new Honorary Editor of the Institute's Journal. MEMBERSHIP The President: I have pleasure in announcing that, their names having been published in accordance with By-law 5.2.2, the following have been elected by Council to membership in the following grades Fellows: W. G. Jayes and F. K. Wright Members: D. W. Penman, A. W. Bryson, and D. L. Gibbs Graduates: R. J. Adey, J. P. Bond, R. C. Dunne, G. M. Entwhistle, J. M. Rendu, J. P. S. Turner, and A. P. van Jaarsveld Associates: A. Ellis, B. R. Hambly, A. J. Johansen, and G. W. Tregoning

Jan 10, 1973

By A. E. Lewis, J. Du Plessis, J. Chivavava

Current metallurgical processes lack selective and efficient REE recovery from aqueous leach liquors. Antisolvent crystallisation is used to selectively recover pure inorganic salts from aqueous solutions without excessive chemical use in ambient conditions. Yttrium sulfate octahydrate (Y2(SO4)3.8H2O) was used as a representative rare earth salt to investigate the effect of antisolvent selection on the crystal morphology and size distribution of the final crystalline product produced through antisolvent crystallisation. The antisolvents of choice were short length alcohols that are water miscible i.e. methanol, ethanol, 2-propanol and t-butanol. All experimental parameters except the type of antisolvent were kept constant under isothermal conditions. The large reduction in solubility of the salt by the antisolvent creates high supersaturations. This leads to high product yields as observed in this study at > 91%. In general, a variety of morphologies were successfully formed in each individual alcohol including; rods, plates, prismatic cubes and starburst clusters. The powder X-ray diffraction (XRD) analysis indicated that Y2(SO4)3.8H2O was the only species present for all final products. There was a change observed from the starburst and rod structures for the shorter alcohols towards prismatic cubes for the longer alcohols due to different strengths in the solute-antisolvent interaction at the crystal growth faces. The crystal sizes increased with an increase in the alcohol chain length because of the lower supersaturation conditions due to a limit in the mass transfer induced by the bulkier alcohol structure. In conclusion, it has been shown that the particle morphology and size can be greatly affected by the selection of antisolvent even under high supersaturation conditions, contributing to understanding the effect of different antisolvents on the final particle characteristics. The engineering of favoured product characteristics can therefore be achieved by antisolvent crystallisation, presenting a viable alternative process for the recovery of REE. Keywords: Antisolvent crystallisation, rare earth elements, morphology, particle size

Jan 1, 2020

By D. H. Diering

Definition of mineral resources and reserves forms the basis for effective mine planning and reliable public reporting of mineral assets. Historically the mineral resource and reserves declaration process has been the domain of the geology and surveying disciplines, with the declaration of the reserves by the surveyor being based on the application of modifying factors to the declared resources available for mining. As part of an ongoing process to improve efficiency, reliability, and reproducibility of results, this approach has been revised and enhanced through the introduction of a revised process and reconciliation tools. The revised approach to reserve definition is based on the definition of scheduled resources, at an appropriate confidence estimate in the context of an approved business plan, over the anticipated life of the mineral asset being applied to define reserves. This planning and scheduling is developed, during the annual business planning process, by the mine planning department using tools such as CADSMine?. The scheduled area together with the application of revised modifying factors is tabulated in the BME (basic mine equation) and reflects the mine production plan over time. Simplification of the modifying factors to dilution and losses underpins the simple yet robust approach to improved definition of reserves in this process and in the basic resource to reserve equation (BR2RE). Dilution intrinsically affects grade but not metal content, whereas the losses reflect both the efficiency of mining and planning and are reflected in metal losses, area losses, or both. Reconciliation of the derived ?resource converted to reserve? area, (which is based on the business plan from CADSMine?), versus the ?resource available for mining?, (which is derived from Datamine?), underpins the robustness and auditability of the reserves declaration. This R&R accounting and reconciliation approach is transparent and facilitates interrogation of the logic and rationale of long-term business planning and project strategy. These numbers are processed and reported in the logic of the basic resource equation (BRE), which also addresses aspects such as white areas (future and historic), tail management, and partial extraction (non-scheduled pillars, etc.) in compliance with SAMREC definitions. Areas that do not have the necessary confidence and data support to be declared as resources find their space as pre-resource (outside the domain of public reporting), outlining existing potential for future extraction and reporting. Use of the BRE leads ultimately to a complete, refined accounting and reconciliation-oriented approach for all production entities. The revised resource and reserve process includes the discipline of mine planning as intrinsic to the definition and declaration of resources and reserves. Subsequent to the change in process, the resources and reserves have truly become the domain of the mineral resource management discipline. This paper defines the logic of the basic resource equations and outlines their application in the definition and reconciliation of mineral resources and reserves at Anglo American Platinum Limited.

Jan 1, 2012

By T. H. Yang, Q. K. Wang, T. Song, J. W. Zhou

The grinding circuit can be one of the most important mineral processing circuits in plants. Along with the application of large-scale milling machines, the design and optimisation of the operation strategy for grinding circuits is more complicated. An in-house grinding process simulation tool was developed to mass balance, model fit and simulate crushing, grinding and classification circuits. An industrial grinding and classification circuit in a copper mine was modelled, and the modelling parameters were verified by a particular group of plant survey data. To justify the prediction ability of the fitted models, the model predictions under different operation conditions were compared with another group of plant survey data. Then the model predicted the effects on the circuit of changing operating conditions. Circuit analysis of the comminution process for water feed to a SAG mill, water feed to sump, the rolling speed of a SAG mill and the percentage of ball filling in a SAG mill was put into practise, based on the simulation results. The simulation results can be used to help plant operators understand the features of the comminution process and may help to build a knowledge library for process control. Keywords: Process modelling, grinding, comminution, circuit analysis

Jan 1, 2020

By B. T. McKenna, H. Nirschl, P. Morsch, B. Fränkle

Generally, filter media used in filter presses have a limited operational life. Besides mechanical damage, there is a growing deposition of fine particles with increasing filtration cycles, the so-called blinding, inside the filter cloth. The resulting decreasing pore diameters not only affect the efficiency of the filtration process itself by increasing the filter medium resistance, but also make it more difficult to regenerate the filter press between the individual cycles, e.g. leading to an insufficient cake discharge. Since tailings filtration requires handling of large process flows containing a significant fraction of particles in the lower micrometer range, an investigation into media rejuvenation is of interest. Keywords: Tailings filtration, filter fabric resistance, filter media regeneration, filter cleaning, intraweave contamination

Jan 1, 2020