Search Documents

By H. M. Stewart, N. F. Dawson, J. P. Beukes, P. G. van Zyl, Q. P. Campbell, A. Jordaan, R. I. Glastonbury, L. N. Sadiki

"SynopsisThe physical properties of oxidative sintered pellets produced from typical South African UG2 ore are compared with the physical properties of pellets produced with conventional South African metallurgical-grade chromite ore (from the Lower Group 6 or the Middle Group 1 and 2 seams). A statistical evaluation of the cured (sintered) compressive strengths proved that pellets prepared from UG2 ore are likely to have the same, or better, compressive strength than pellets prepared from metallurgical-grade chromite ore. The cured abrasion strength of the UG2 pellets was also superior to that of the metallurgical-grade pellets. Scanning electron microscopy (SEM) backscatter, secondary electron, and elemental X-ray mapping were used to determine the reasons for the general superior strength of the UG2 pellets. The case study UG2 ore also required 13 kWh/t less energy for milling to attain the required particle size distribution prior to pelletization, which can lead to substantial cost savings. Results presented in this paper can be utilized by ferrochromium (FeCr) producers to better quantify the advantages and disadvantages associated with the use of UG2 ore for FeCr production.IntroductionChromite, a mineral of the spinel group, is the only commercially viable source of virgin chromium units. Geologically, commercial chromite deposits in the world are found in three forms, i.e. alluvial-, podiform-, and stratiform-type deposits (Murthy et al., 2011; Cramer et al., 2004). Alluvial deposits were formed by weathering of chromite-bearing rock with the subsequent release of chromite and gravity concentration by flowing water. However, these deposits are relatively small and of comparatively minor commercial interest. Podiform-type chromite deposits usually occur as irregularly shaped pods or lenses, and their distribution within a mineralized zone is usually relatively erratic and unpredictable, making the exploration of these deposits difficult and costly (Cramer et al., 2004). Stratiform-type chromite deposits occur as parallel seams in large, layered igneous rock complexes with more regular layering and lateral continuity (Cramer et al., 2004). The largest example of a stratiformtype chromite deposit is the Bushveld Complex (BC) in South Africa, which holds an estimated three-quarters of the world’s viable chromite ore resources (Cramer et al., 2004).Several chromite seams exist in the BC. The seams of economic interest are the Lower Group 6 (LG6), the Middle Group 1 and 2 (MG1 and 2), and the Upper Group 2 (UG2) seams (Cramer et al., 2004). The LG and MG seams are specifically exploited for their chromium content, while the UG2 seam is mined primarily as a source of platinum group minerals (PGMs) (Xiao and Laplante 2004). Extraction of the PGMs from the UG2 ore usually involves the liberation of the sulphide by milling and subsequent recovery of the PGM concentrate through flotation (Xiao and Laplante, 2004). Chromite in the PGM concentrate is undesirable; therefore, PGM recovery circuits are specifically designed to ensure maximum rejection of the chromite to the tailings stream. However, the chromite in the PGM tailings can potentially serve as feedstock for ferrochrome (FeCr) production, after beneficiation to increase the chromium content."

Jan 1, 2015

By E Matinde, M. Mnisi, I. C. Thobadi, W. Clark, J. D. Steenkamp

Pyrometallurgical smelters utilise tap-holes, through which liquid metal, matte and/or slag are tapped at regular intervals. However, tap-hole failures can have a devastating impact on smelters, which includes loss of equipment, human life and business interruptions. Contributing factors to tap-hole failures include poor and/or incorrect refractory material selection, including tap-hole clays. The functions of tap-hole clays in smelters include their ability to be extruded and drilled with ease at the end and beginning of a tap, and their ability to resist chemical wear due to molten metal and slag during tapping. Mintek is currently developing methods of evaluating properties of tap-hole clays with a specific focus on workability, and wear mechanisms of clays due to ferrochrome alloy and slag. Of particular interest to this study was the characterisation of various tap-hole clays. This paper evaluates the chemical and phase chemical properties of three different tap-hole clays. The bulk chemical composition of the tap-hole clays was determined by inductively coupled plasma optical emission spectroscopy, proximate analyses and combustion methods. The bulk phase compositions and specific phase chemical compositions were studied using quantitative X-ray diffraction, scanning electron microscope and electron probe microanalyses techniques. Keywords: Tap-hole clay, chemical analyses, phase chemical analyses, ferrochrome

Jan 1, 2020

By C. Erichsen

ABSTRACT: The Berg Bock Freeway Tunnel represents the southernmost link of the "Thuringian tunnel chain" of the new freeway A71 located in the eastern part of Germany. It comprises two tubes each 2700 m in length. From north to south, it passes through the Suhl granite, the base sediments and the porphyrite of the New Red as well as the layers of the Middle Bunter. The two tunnel tubes were driven by the shotcrete method within appr. 10 months. With four tunnel faces, maximum performances totalling appr. 30 m/d were attained. Additional, supplementary demands on the safety conception, resulting from the findings from and the analysis of fire accidents in tunnels in recent years, had to be fulfilled in the execution planning at short notice. The inner lining is largely constructed using non-reinforced concrete. Reinforcement is only installed in the portal zones, in tunnel sections in less stable rock and in areas with a special cross-section as for instance cross connections and niches. ZUSAMMENFASSUNG: Der Autobahntunnel Berg Bock stellt das südlichste Glied der "Thüringer Tunnelkette" auf der Autobahn A71 dar, die im Osten von Deutschland liegt. Er besteht aus zwei Röhren von je 2700 m Länge. Vom Norden nach Süden durchörtert er den Suhler Granit, die Basissedimente und den Porphyrit des Rotliegenden, sowie die Schichten des Mittleren Buntsandsteins. Die beiden Tunnelröhren wurden in Spritzbetonbauweise in einer Bauzeit von etwa zehn Monaten aufgefahren. An vier Vortriebsorten wurden Spitzenleistungen von insgesamt etwa 30 m/d erzielt. Ergänzende Anforderungen an das Sicherheitskonzept, die sich auf der Grundlage der Auswertung der in den letzten Jahren aufgetretenen Brandunfälle in Tunneln ergeben haben, wurden im Rahmen der Ausführungsplanung kurzfristig berücksichtigt. Die Tunnelinnenschale wurde weitgehend aus nicht bewehrtem Beton hergestellt. Nur in den Portalzonen, in Tunnelabschnitten mit weniger standsicherem Fels und in Bereichen mit speziellen Querschnitten, wie beispielsweise im Bereich von Querstollen und Nischen, wurde bewehrter Beton ausgeführt. RÉSUMÉ: Le tunnel d'autoroute de Berg Bock représente le plus méridional maillon de la "chaîne thuringienne de tunnels" sur l'autoroute A71 dans l'est de l'Allemagne. Il se compose de deux tubes d'une longueur de 2700 m chacun. Du nord vers le sud, il traverse le granit de Suhl, les sédiments de base et le porphyrite du Rotliegendes, aussi que les strates du grès bigarré intermédiaire. Les deux tubes étaient creusés en méthode de construction de béton projeté dans une période de construction d'environ dix mois. À quatre fronts de taille rendements maximaux collectifs d'environ 30 m par jour étaient obtenus. On a eu égard à court terme dans la conception d'exécution à des demandes supplémentaires vers la conception de sécurité, qui ont résulté sur la base de l'interprétation des accidents d'incendie dans des tunnels dans les années dernières. La paroi intérieure était construite largement de béton non armé.

Jan 1, 2003

By S. Budavari, F. M. C. C. Vieira

For several decades, the deep, gold-bearing reefs of the Witwatersrand basin have been mined predominantly according to layouts characterised by longwalls with strike pillars to provide regional support. During the past few years, a new generation of mining layouts has been introduced. These layouts are based on the concept of grid-type, scattered mining with dip pillars for regional support. As the extraction of the gold reefs extends to depths below 3500 m, the hazards associated with mining at these ultra-depths are expected to increase to unacceptable levels. Therefore, the question arises as to, which of the currently applied mining layouts is most acceptable for the economic and safe extraction of an ultra-deep orebody. The purpose of this paper is to describe a research investigation carried out to evaluate the degree of acceptability, from the rock engineering view point, of four currently used mining layouts for application at a depth-range of between 3500 and 5000 m. Pendant plusieurs décades, les filons d’or profonds du bassin du Witwatersrand ont été exploités d’une manière prédominante selon des dispositions caractérisées par des longues tailles avec des piliers directionnels pour donner un support local. Les dernières années ont vu la naissance d’une nouvelle génération de dispositions de mine. Ces dispositions sont basées sur le concept d’extraction type grille, éparpillée, avec des piliers au pendage pour le support local. Comme l’extraction des filons d’or va à des profondeurs en dessous de 3500m, il faut s’attendre à ce que les risques associés à l’exploitation à ces profondeurs extrêmes atteignent des niveaux inacceptables. Par conséquent, la question se pose de savoir laquelle des dispositions de mine couramment utilisées est la plus acceptable pour l’extraction rentable et sans danger d’un gisement ultra profond. Le but de l’étude présente est de décrire les recherches exécutées pour évaluer le degré d’acceptabilité, du point de vue d’ingénierie de roche, de quatre dispositions de mine couramment utilisées pour application à un rayon de profondeur entre 3500 et 5000m. Die tiefen, goldträchtigen Riffs des Witwatersrandbeckens wurden über einige Jahrzehnte hindurch vorwiegend nach jenen Layouts abgebaut, die von Langfrontstreben mit Schlagpfeilern charakterisiert waren, um regionale Unterstützung zu gewährleisten. Während der letzten Jahre wurde eine neue Generation von Grubenlayouts eingeführt. Diese Layouts basieren auf dem Konzept der Rasterfeld-Art, gestreuter Bergbau mit Neigungspfeilern für regionale Unterstützung. Es kann erwartet werden, daß auf Grund der Tatsache, daß sich die Extraktion der Goldriffs auf Tiefen unterhalb 3500 m verlagert, die Gefahren, die mit dem Bergbau an diesen Ultratiefen verbunden sind, sich auf ein nicht annehmbares Niveau erhöhen. Folglich erhebt sich die Frage, welche der gegenwärtig angewendete Abbaulayouts für die ökonomische und sichere Extraktion eines ultra-tiefen Erzkörpers am annehmbarsten ist. Zweck dieser Arbeit ist es, eine durchgeführte Untersuchung zu beschreiben, die vom Gesichtspunkt der Gesteinstechnik gesehen, vier gegenwärtig angewandte Abbaulayouts für den Einsatz in einem Tiefenbereich zwischen 3.500 und 5.000 m evaluiert.

Jan 1, 2003

The 101 st Annual General Meeting of The South African Institute of Mining and Metallurgy was held in the Gold Room, Transvaal Automobile Club, 60 5th Street, Lower Houghton, Johannesburg on Wednesday, 12th August, 1998. Obituaries The President announced the death, during the year, of the following members: Honorary Life Fellows and Past Presidents H.E. Cross, D.G. Malan, P.W.J. van Rensburg Life Fellows J.B. Rolfes, W.C. Walmsley Fellows H.F. Boshoff, M.L.A. Fitzgerald, J. Humphriss Retired Fellows H.S. Botha, E.Collier, J.L. Curtis, A.H.H. Davison, D.I. Legge, B.D. McNeice, J.A. Northcott, D. de V. Oxford, S.S.K. Penney, P.C. Pirow, J. Pope, A.J. Rossouw, A.N. Shand, E.P. Smit, H.V. Solomon, S.G. Taussig

Jan 1, 1998

By M. Abdellatif

"SynopsisCalcined basic nickel carbonate (BNC) concentrate was smelted in a pilotscale DC arc furnace to produce a nickel metal. The furnace was continuously operated for 12 days (24 hour/day), during which twelve different smelting conditions were investigated, with the major variables being reductant type and feed rate, flux composition and addition, and BNC feed rate.The 200 kW DC arc furnace was operated at power levels between 110 and 165 kW and at a total feed rate of 78 to 96 kg/h, resulting in an average slag and metal tapping temperature of about 1650°C. A total of 7.2 t of BNC were smelted, producing about 5.44 t of nickel metal and 2.94 t of slag. Nickel recoveries of 96.4% and higher were achieved, and the slag nickel content was as low as 0.1%. The major impurities in the metal were iron (mostly from oxygen lancing) and carbon. The calculated feed carry-over was less than 0.85% and the graphite electrode consumption was between 2.8–3.3 kg/MWh.IntroductionOne of the most distinctive advantages of DC open-arc smelting is the ability to process fine raw materials without any major issues with regard to the operability of the furnace, metal recovery, and metal quality. This has been demonstrated in Mintek’s DC arc pilot plant facilities over a period of about three decades (Curr et al., 1983). The materials that have been processed include laterite (Kotze, 2002), chromite fines (Curr et al., 1983), manganese fines (Lagendijk et al., 2010), PGM concentrates (Shaw et al., 2013), electric arc furnace (EAF) dust (Denton et al., 2005; Abdellatif, 2002a) and stainless steel (SS) dust (Denton et al., 2005; Abdellatif, 2002a; Goff and Denton, 2004), and petroleum fly ash (Abdellatif, 2002b). The top particle size of such materials can vary from a few millimetres (e.g. laterite) to micrometres (EAF and SS dust). Dusting, whether due to physical carryover of feed or to the arc side reactions, has been proven to be a non-issue. As such, the applications of DC open-arc furnaces have the potential to be extended to other raw materials such as particulate nickel oxide, which has a particle size much less than 100 µm.Nickel oxide is typically produced from laterite ore by sulphuric acid leaching, purification, and precipitation as basic nickel carbonate (BNC) (Rhamdhani, Jak, and Hayes, 2008) or as mixed hydroxide precipitate (MHP) (Mackenzie, Virnig, and Feather, 2006), and finally calcining at moderate temperatures (800–1200°C). The NiO product is very fine, with an average particle size in the range of 10–20 µm and a NiO content of more than 99%."

Jan 1, 2015

By W. L. Van Heerden

In situ complete stress-strain characteristics of large coal specimens by W. L. VAN HEERDEN, B.Sc. Hons. (Pret.) (Visitor) The significance of ;n situ tests on large coal specimens is briefly reviewed. Tests aimed at obtaining complete stress-strain characteristics of large coal specimens with high width-to-height ratios are described. A formula for the relationship between strength and width-to-height ratios of coal pillars is proposed, and the influence of width to- height ratios on the deformation characteristics of pillars is discussed.

By S. T. L. Harrison, J. R. Amaral Filho, M. Smart, J. Broadhurst, J. Weiler

Technosol production from mine waste, following amendment with additional organic residues, to provide healthy and functional topsoil is an advantageous alternative to the long-term dump disposal of mine waste. Minimising the legacy of mine waste and supplying soil for mine site rehabilitation contributes towards more sustainable mining practices. Following the creation of the physicochemical structure of the soil from appropriate mixtures of coal waste with low sulfur content, physical ameliorants and nutrient sources, the inoculation of Technosols with active microbial suspensions may accelerate the decomposition of organic matter present and ensure nutrient availability for plant growth through active nutrient cycling, particularly of nitrogen, sulfur and phosphorous. In this paper, South African ultrafine coal waste was used as the main mineral matrix, and malt residue was used as source of organic matter and nutrients. In order to evaluate the effects of Technosol inoculation, five microbial treatments were used, including the addition of: commercial grade efficient microorganisms (EM Prosoil), anaerobic digested sludge supernatant from treating brewery waste, and ‘tea’ extracts prepared from compost, vermicompost and soil native to the mining area. Growth experiments were carried out using Eragrostis teff, commonly known as teff, a grass typically used for the rehabilitation of mined areas in South Africa. Preliminary results showed that Technosols inoculated with microorganisms performed better in terms of nutrient availability and plant growth. Varied performance was observed as a function of the microbial inoculation applied. This suggests that the inoculation of Technosols with appropriate microorganisms may be recommended to accelerate nutrient availability assisting plant growth during the initial establishing of the Technosols. Technosols continue to show promise as an alternative to both mine waste disposal and the burrowing of topsoils for mine rehabilitation. Keywords: Fabricated soil, mine waste, coal discards, malt residue, nutrient availability, soil microbiology, plant growth

Jan 1, 2020

By A. Mehmet

The feasibility of employing a multi-stage column for the recovery of gold from cyanided pulps using extruded carbon was investigated on a pilot-plant scale. It was anticipated that the column contactor would have certain advantages over conventional carbon-in-pulp plants. The feed pulp was screened to remove particles larger than 200 µm and was diluted to a solids concentration of about 23 per cent. The column was operated continuously for 24 days at a pulp flowrate of about 60 l/min and a carbon flowrate of 44 litres per day. The average gold concentrations in the barren pulp 12 hours and 24 hours after the carbon transfer were 0,012 and 0,031 mg/l respectively. The average gold concentration in the solution phase in the feed was about 2,0 mg/L. The average gold Loading on the carbon was 6290 g/t. Calcium carbonate was removed from the loaded carbon by treatment with 0,5 bed volumes of 2,8 per cent hydrochloric acid solution at ambient temperature. The calcium concentration was reduced from about 17 000 to about 500 g/t The carbon was eluted by the Zadra procedure at atmospheric pressure. The results of the elution were highly satisfactory, the gold concentration being reduced from about 6000 to about 20 g/t in 48 hours. The eluted carbon was regenerated in a Rintoul kiln at about 700°C. The activity of the regenerated carbon was found to be at least as high as that of fresh carbon.

Jan 1, 1992

By V. Jokovic

Hydrocyclones are the most commonly used classifiers in the mining industry. The reason for this is their low operating cost and a small footprint. Data from plant trials where screens replaced hydrocyclones indicated that lower bypass of fines and sharper separation could improve breakage rates, with a positive effect on flotation circuit performance throughput. Despite the importance of classification, hydrocyclones have not received as much attention as more expensive comminution units, and their technological progress has been incremental. Noticeable water split (Rf) reductions of a semi-inverted hydrocyclone have been reported in the past. According to theory, the hydrocyclone with reduced Rf will improve classification of fines. A classification study using semi-inverted hydrocyclones was conducted to determine if a hydrocyclone could be operated in a way that would minimise misclassified fines. The classification performance of a semi-inverted hydrocyclone will be presented in this paper and other potential applications will be discussed. Keywords: Semi-inverted hydrocyclone, water split, misclassification of fines

Jan 1, 2020

By S. Durapraj, R. T. Masethe, U. Maqina, A. C. Adoko

This study investigates seismicity and rockburst control within the Merensky Reef and UG2 orebody of an intermediate-depth platinum mine located in South Africa's Bushveld Complex. Utilising a mine-wide seismic monitoring system, over 1,900 seismic events were recorded between April 2023 and May 2024, revealing complex seismic patterns driven by mining-induced stress changes. The largest event, with a magnitude of ML 2.0, underscores the seismic risks associated with mining at increasing depths. Key findings include the spatial and temporal variability of seismic events, with high seismic activity observed near pillars and geological structures. A significant portion of events correlated with pillar and foundation failures. Moment tensor analysis identified dominant failure modes, such as stress-driven fracture closures and dynamic pillar failures. To mitigate risks, the study emphasises advanced support system redesign and rockburst risk assessment using the rockburst damage potential (RDP) method. The research highlights the importance of monitoring, geotechnical compliance, and adaptive designs in enhancing safety and reducing seismic hazards in underground mining operations. The study applied the RDP framework, classifying damage across R1 to R5 scales, where most instances fell into low-risk categories (R1 and R3), indicating minor to moderate damage. However, data limitations and the tabular stoping method's complexity led to inconclusive results, highlighting the need for more robust data and customised risk assessment tools. Despite these challenges, the RDP approach provided valuable insights into rockburst mechanisms and the effectiveness of existing support systems.

Jan 12, 2025

By S. Mohanta, I. D. Behera, B. Sahoo

"Run-of-mine coal contains particles of different sizes with different specific gravities, and when this coal is crushed, the amount of material present in a particular density class changes. This alters the washability characteristics of the coal, which affects the quantity, quality, and separation efficiency of the gravity-based coal washing process. The degree of difficulty in washing a typical coal at a particular specific gravity depends mostly on the amount of material occurring within ±0.1 specific gravity range, which is known as ‘near-gravity material’ at that particular specific gravity of separation. In this paper, two numerical indices, namely ‘near-gravity material index’ and ‘index of washability’, are used to quantify the distribution of near-gravity material in different density classes and to evaluate the degree of difficulty involved in the washing process. The results of this preliminary investigation indicate the uniform distribution of near-gravity material in all density classes for finer size fractions, whereas for coarser size fractions more near-gravity material is present in the lower density classes, making the washing process more difficult at a lower specific gravity of separation. IntroductionThe prime objective of coal beneficiation is to remove physical impurities as effectively and economically as possible. The beneficiation process includes various operations on the asmined coal to make it more suitable for enduse application without destroying the physical identity of the coal. There are several coal beneficiation processes, but gravity-based separators remain the most efficient unit operation for removing the undesirable gangue material from run-of-mine coal. These separators exploit the difference in density between coal particles and gangue particles to effect a separation. The feed is introduced into an aqueous suspension of ultrafine magnetite with a particular density. The feed particles with a relative density less than that of the suspension (clean coal) float to the top surface of the suspension, whereas particles denser than the suspension density (gangue material) sink to the bottom. When the difference in density between the particle and the aqueous suspension is large, the separation is easy, but when this difference is less the separation becomes much more difficult since the settling velocity of the particles is very low. This lower settling velocity increases the probability that particles that should report to floats report to sinks, and vice versa, hence increasing the amount of misplaced material. Therefore, the degree of difficulty in beneficiating a typical coal at a particular specific gravity depends on the amount of material occurring within ±0.1 specific gravity range. This is known as ‘neargravity’ material, also termed ‘near-dense’ material, at that particular specific gravity of separation."

Jan 1, 2016

By I. R. Phimister

'Ancient' mining near Great Zimbabwe I. R. PHIMISTER. B.A. Hons. (Nottingham). B.A. Spec. Hons. (Rhodesia) (Visitor) In proposing reasons for the geographical location of Great Zimbabwe, the paper re-examines the popular assumption that Zimbabwe is comparatively remote from the known areas of 'ancient' goldmining. The lack of 'ancient' workings in the neighbourhood of Zimbabwe is pointed out, and it is suggested that the mining of placer deposits of gold may have played some part in the development of Zimbabwe on its particular site.

Jan 1, 1974

By B. Nemutudi, X. Zhang, B. McFadzean, P. E. Ngoepe, P. P. Mkhonto, S. Pikinini

The comparison study on adsorption of potassium normal butyl xanthate (PNBX) and sodium (nbutyl) dithiocarbamate (SNBDTC) on sperrylite mineral forms a basis in understanding the floatability improvement and paves a way for the design of collectors that may impact on a wide range of arsenide minerals. This study used a computational density functional theory (DFT) and experimental microcalorimetry approach to determine the adsorption energies of PNBX and SNBDTC collectors onto a sperrylite mineral surface. From a computational aspect, we considered the most stable surface plane of (100) surface, which had been found to give the lowest surface energy, compared to the other surface planes. It was observed that the PNBX and SNBDTC preferred to bridge on the As and Pt atoms through the S atoms. These findings showed that the collector adsorbed on the surface through both Pt and As atoms and indicated that the As atoms were significantly active in the adsorptions. We found that the adsorption energies were in the order: SNBDTC (–278.38 kJ/mol) > PNBX (–270.92 kJ/mol), indicating that the dithiocarbamate had stronger exothermic adsorption than the xanthate. From the microcalorimetry test it was also found that the SNBDTC was more exothermic than the PNBX and the adsorption energies were: SNBDTC (–473.50 kJ/mol) > PNBX (–331.13 kJ/mol). These results showed that the nitrogen atom in the SNBDTC collector had a great influence on the adsorption strength of the collector on the mineral surface. This is due to the electron deposition behaviour of nitrogen atoms compared to the electron withdrawing character of oxygen and as such the SNBDTC showed better collecting ability than the PNBX. These results paved the way for the design of collectors for sperrylite and other arsenide minerals and suggested that nitrogen in a collector may significantly improve the ability of the collector for improved recovery. Keywords: Computational modelling, microcalorimetry, SNBDTC and PNBX collectors, adsorption energies

Jan 1, 2020

The June General Meeting of the Branch was held in the St. Helena Club on Wednesday, 18th June, 1969. Mr J. G. Kirchner (Chairman of the O.F.S. Branch) was in the chair. There were also present: Eight Members: Messrs A. F. Leger, J. N. Saunders, T. Zadkin (Committee Members), Messrs M. G. Cullen, M. S. Grobler, C. J. Isaac, S. L. S. Swart, P. S. Turner. Eight Associate Members: Messrs R. Campbell, D. E. Couperthwaite, J. D. Couperthwaite, A. Hepburn, P. A. Hoffman, H. J. Reeders, R. B. Sutherland, P. R. Wheeler. Two Graduates: Messrs M. T. G. Davies, B. D. Goodwin. Two Affiliates: Messrs L. D. Hulley, K. L. Wilson. Three Visitors. Total Present: 24. Apologies were received from Mr L. O. W. Leimer. The Chairman declared the meeting open and, after extending a welcome to all visitors, said that it was his sad duty to announce the recent death of Mr. R. Jack, Associate Member. As a mark of respect to the deceased and in sympathy with the bereaved, those present stood in silence for a few moments. MINUTES OF PREVIOUSGENERALMEETING The Minutes of the Previous General Meeting held on the 19th February, 1969, which were published in the April Journal, were taken as read and their adoption proposed by Mr J. N. Saunders and seconded by Mr D. E. Couperthwaite. MA TTERS ARISING FROM THESE MINUTES There were no matters arising from these minutes. ELECTION OF SCRUTINEERS Mr V. J. Isaac proposed and Mr M. S. Grobler seconded a motion that Messrs J. G. Kirchner, J. N. Saunders and M. G. Cullen be elected scrutineers in the forthcoming election of Committee Members. GENERAL BUSINESS The Chairman announced that a visit to the South African Railways Workshops in Bloemfontein had been arranged for the 23rd July, 1969 and expressed the hope that this would be well patronised. TALKS The Chairman called first on Mr D. E. Couperthwaite to present his paper on 'Heavy media separation' and then on Mr A. F. Leger to present his paper on 'Engineering plastics'. Both presentations, which were illustrated with diagrams, proved of great interest to all members. A vote of thanks to both speakers was proposed by Mr T. Zadkin. CLOSURE After thanking the speakers, the Chairman thanked all present for their attendance and declared the Meeting closed at about 9.30 p.m. Refreshments were then served.

By J. W. Drelich, H. Zeng, L. Xie, X. Cui, Z. Gao, M. Tian, Y. Hu, W. Hu, W. Sun

Flotation is a mineral separation technology that uses the surface hydrophobic difference of valuable minerals and their associated gangue minerals to separate them. The flotation collector adsorbs on the valuable mineral surface to improve its hydrophobicity, and metal ions are usually used as activators to enhance the collector adsorption. Different mineral surfaces show different charging properties and adsorption behaviours with the collector or metal ions. Moreover, the order of adding metal ions and the collector also show significant and different flotation performance for the same mineral. The adsorption or flotation behaviour or both are governed by mineral surface chemistry, such as surface charging and reactivity. In our recent studies, force measurement using atomic force microscopy (AFM) was employed to study the surface charging and adsorption mechanism of metal ions and collectors. By preparing collector-functionalised AFM tips, AFM can directly measure the adsorption strength of the collector on the mineral surface to determine the anisotropy of mineral surface reactivity. The preparation of collector-functionalised AFM tips provides the foundation for further study of the activation role of metal ion in the collector adsorption. The application of AFM for force measurement in the surface chemistry of mineral flotation can provide important information on developing flotation reagents and lays the foundation for the specific regulation of mineral surface characteristics. Keywords: Scheelite; flotation; surface chemistry; AFM force measurement

Jan 1, 2020

By H. Jiang, W. Wang, Y. Zhao, J. Qiao, C. Duan

DEM simulations were used in this research to study the screening process of a novel variable amplitude equal thickness vibration screen (VAETVS). The response regularity of mass distribution and granular moving velocity at the different screen panels to feed rate was investigated and the predictive model for the unit area processing load was proposed. The influence of aperture size, the size variance, and the opening ratio on the mass passing-distribution and overall screening performance, respectively, were revealed. The results showed that the response model of the unit area load Ф to the feed rate Q can be concluded as Ф∝0.324×Q. The moving velocity of particles also showed a positive relevance to the feed rate, besides which the passing rate of fine-grained material at the feed end was negatively related to the aperture size, while the case was reversed in the feed end. The increase of aperture variance AV enhanced the passing ability of small particles at the feed end,and reduced the misplaced ratio of the large particles at the discharge end. A better screening efficiency can be obtained when the average aperture size of the entire sieve is 7.5 mm, with the aperture variance of 1 mm between the adjacent panels. When the combination of the opening ratio is 35-35-40, a better screening effect can be achieved. Keywords: Equal thickness screening, DEM, particulate velocity, mass distribution regulation

Jan 1, 2020

By P. C. Pistorius, M. P. Maphutha, J. D. Steenkamp

Advanced high-strength steels (AHSS) are sophisticated materials being developed by the steel industry to mitigate challenges related to the performance of motor vehicles. To meet the requirements of AHSS, the ferromanganese alloys (FeMn) utilized in the production of the steel are required to contain acceptable levels of unwanted impurities, i.e. P, S, N, H, and C. The focus of the current study was to investigate dephosphorization of ferromanganese to produce a low-P alloy that could be effectively utilized in the production of AHSS. The study involved conducting laboratory-scale testwork to study the efficiency of CaO-based slag systems to dephosphorize FeMn alloys. The addition of Na2O, CaF2, and BaO to MnO-CaO-SiO2 slag was considered. The test work was carried out in a 25 kW induction furnace at temperatures of 1350°C, 1400°C, and 1450°C. The P partition coefficient (Lp) remained small at <1, which is an indication that dephosphorization had not been achieved. The baseline slag, comprising 40%CaO-40%SiO2-20%MnO, reported higher Lp values. Addition of Na2O and CaF2 did not show any further benefit. Substituting half of the CaO by BaO, resulted in similar Lp values to those of the baseline slag under conditions of 1350°C and 1450°C at 30 minutes. In summary, based on the Lp values obtained, the conditions investigated with the CaO-based slags appeared to have been unfavourable for dephosphorization of FeMn alloys, as most of this impurity element remained in the alloy.

Sep 1, 2021

By D. van Rensburg

Jointed rock slopes are generally stable, as there is no freedom of movement for blocks of rock. In an open- pit mining environment, blasting opens up space into which blocks of rock can fail, resulting in the common occurrence of slope failure. Prior to the blasting of a trim pattern, the immediate highwall is scaled, where loose rock material is removed by means of a mechanical scaler. As mining of the pit progresses, the height of the scaled highwall from the pit floor progressively increases. These highwalls are never scaled again for the remainder of the pit life, and time-dependant deterioration contributes to these highwalls becoming subject to rockfall and, sometimes, slope failure. This paper documents the development of a South African innovation, a remote-controlled mechanical highwall scaler, a world first for the mining industry. The scaler will enable open-pit highwalls to be scaled from crest to toe whenever the need arises. It will reduce the risk associated with highwalls and deliver on the Anglo American promise of producing safe, profitable platinum.

Jan 1, 2012

Council for 1998/99 President R.P. Mohring President Elect J.R. Dixon Vice Presidents Senior junior M.H. Rogers Dr L.A. Cramer Immediate Past President Honorary Treasurer Dr N.A. Barcza J.A. Cruise

Jan 1, 1985