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Your Council has pleasure in submitting its report for the year ended 30th June, 1970. COUNCIL The following served as Office Bearers during the year under review: Messrs J. K. E. Douglas (President), V. C. Robinson and Prof D. D. Howat (Vice-Presidents), R. C. J. Goode (Immediate Past President) and D. G. Maxwell (Honorary Treasurer). Members of Council: Mr. R. J. Adamson, Dr. M. G. Atmore, Mr M. Barcza, Dr J. M. Bereza, Messrs H. Britten, H. E. Cross, A. R. C. Fowler, G. W. Holl, Dr J. P. Hugo, Messrs N. A. Honnet, P. Lambooy, Prof J. de V. Lambrechts, Mr C. E. Mavrocordatos, Dr J. T. McIntyre, Messrs J. Meintjies, T. C. A. Meyer, J. A. Nixon, Prof R. P. Plewman, Dr R. E. Robinson, Messrs J. F. Reid, H. Simon and P. W. J. van Rensburg. Ten Council meetings were held during the year with an average attendance of seventeen and the standing committees held 45 meetings. FINANCE The annual accounts, which are attached to this report, show an excess of expenditure over income of R4,608 compared with R2,124 last year. This deterioration can be attributed largely to two important factors, namely an increase in secretarial fees of RI, 789 and an increase in the loss on the Journal from R2,343 to R3,508. In addition, our contribution to the expenses of the Federation of Societies of Professional Engineers increased by R607 from R549 to R1,156. The increase in secretarial fees is partly due to our increased demand for services and partly to increased salaries. In order to maintain its essential services it has been necessary for the A.S. & T.S. to increase salaries in order to keep pace with commerce and industry. With regard to the Journal, we did not expect immediate dramatic results from the changes that were effected as from the beginning of last year in the arrangements for publication. However, the improvement has been even slower in materialising than we expected. This situation is being watched carefully and we will not hesitate to make further changes if necessary. It became clear early in the year that the financial position was deteriorating and your Council decided that it was essential to meet the situation by raising subscriptions and entrance fees. At the same time it was decided that there are no grounds for a distinction between Town and Country members and that in future the scale for the compounding of subscriptions should be based on anticipated future membership, rather than past membership. These changes have had only a minor effect on the accounts under consideration. The MacArthur Forrest Memorial Fund shows an excess of income over expenditure of R132 and the total fund was, therefore, increased by this amount to R4,338. The balance sheet shows that the market value of quoted shares and debentures decreased during the year from R13,059 to R6,567, while accumulated funds now amount to R17,959 compared with R22,567 last year. It will also be noted that we are holding R25,844 on behalf of the Symposium on Opencast Mining. MEMBERSHIP Twenty-eight Fellows, twenty-four Members, seventeen Graduates, twenty-five Associates and twenty-seven Students were elected during the year. Four Members were admitted to Life Membership; Five Members were transferred to the grade of Fellow; one Student was transferred to the grade of Member; two Graduates and one Student were transferred to the grade of Member; six Students were transferred to the grade of Graduate; One Associate was transferred to the grade of Fellow; One Associate was transferred to the grade of Graduate. One Fellow, one Member, six Graduates, four Affiliates and ten Students were removed from the Membership Roll in terms of by-law 7.7.1. Your Council records with deep regret the death during the year, of the following: R. A. H. Flugge-de-Smidt, C. S. McLean, Dr H. J. van Eck, (Honorary Life Fellows), J. C. Humphreys, O. Lazar (Life Fellows), D. G. Beadle, J. G. Craig, P. U. Fisher, R. G. McConnell, J. H. Moore, S. Sterling, L. R. Ulyate (Fellows), H. H. Burger, E. A C. Dickson, R. Jack, S. Ring (Members), M. J. Worrall (Graduate). A comparative statement of the membership as at 30th June, 1970, and the end of the previous year is shown in the following tabulation: 30th June 30th June Honorary Life Fellows 10 8 Honorary Fellows 6 6 Life Fellows 189 191 Fellows 514 530 Members 448 465 Graduates 68 80 Associates 155 172 Students 162 161 1,552 1,613 RECLASSIFICATION OF MEMBERSHIP The designations of grades of membership were altered to accord with the practice in professional institutes both here and overseas and members were advised of the new classifications. MEMBERSHIP DRIVE A committee was established to organise a drive for membership as it was felt that there are numbers of persons in our mining and metallurgical industries who are not yet members but who qualify for membership. Members of the committee were allocated responsibility for campaigning in sections of industry and for publicising the aims, objectives and advantages of belonging to the Institute.

By J. D. Steenkamp, J. Muller

"Excavation of an industrial-scale submerged arc furnace, utilized in the production of silicomanganese, identified two high-wear areas in the refractory lining: the tap-hole, built with cold rammed carbon paste and SiC bricks, and the hearth, built with cold rammed carbon paste. To obtain insight into the potential causes of wear, thermodynamic calculations were conducted on eight sets of data, obtained for seven furnaces on three plants based in South Africa. FACTsage software and associated databases – FACTPS, FToxid, and FSstel – as well as the Mn-Fe-Si-C database of Tang and Olsen (2006), were applied. Theoretical indications are that chemical reaction between carbon refractory and slag, as well as dissolution of carbon and SiC refractory in metal, contributed to tap-hole refractory wear; and dissolution of carbon in metal contributed to hearth refractory wear. IntroductionDuring the excavation of a 48 MVA submerged arc furnace (SAF) used for silicomanganese (SiMn) production, it was found that the taphole and hearth were high refractory wear areas (Steenkamp, 2014). In both these highwear areas, carbon-based cold ramming paste formed the hot face refractory lining (crucible). The wear profile of this SAF is presented in Figure 1.The hot face refractory lining was formed by cold ramming of high-grade carbon ramming material. This material consisted of 50–70% anthracite, 15–25% graphite, 6–12% resin, 2–7% tar, 1–5% clay, and 1–5% alumina. The tap-hole was built using SiC bricks, consisting of 75% SiC, 23.4% Si3N4, 0.3% Fe2O3, 0.3% Al2O3, and 0.2% CaO.In the tap-hole area, the wear of the SiC refractory material was estimated at 0.4 t, and that of the high-grade carbon ramming material, at 1.9 t (Steenkamp, Pistorius, and Tangstad, 2015). The amounts of slag and metal tapped during six years of operation of the tap-hole (September 2007 to April 2013) were estimated at 33 088 t (Steenkamp et al.,2015) and 41 360 t, respectively."

Jan 1, 2016

By K. Dagdelen , S. K. A. Owusu

Uncertainty with regard to estimated grades and tonnages of a mineral deposit demands risk assessment in order to build investor confidence and attract the interest of other stakeholders in the success of a project. Uncertainties associated with Mineral Resource estimates can lead to unreliable production schedules and unpredictable cash flows. However, the techniques used in the mining industry to determine these uncertainties are inconsistent, because the important decisions taken in the process are solely dependent on the responsible Competent Person (CP), without limitations. This leads to disparities between different CPs’ results, using data-sets from the same drill-holes. The various standard codes for public disclosure provide guidelines and recommendations for the classification of Mineral Resources and Reserves but do not provide details on, for example, the amount of geological and geostatistical information needed to qualify for each category of Resources and Reserves. The parameters used to generate the classification categories are subjectively assumed by the responsible CP. In this paper we investigate the impacts of different CPs’ judgements on resource classification, using the same data-sets. The results underpin the need for the mining industry to develop a uniform Mineral Resources and Reserves classification framework that can minimize or avoid significant discrepancies that lead to potential misleading public disclosures.

Aug 8, 2024

By Huanhuan SU, Jianqiang Zhang, Zhongyuan Liu, Junwei Ma

The high-sulfur bauxite in Henan Province was used as raw material. The grinding fineness, pH value and collector dosage on its desulfurization performance, and industrial flotation desulfurization process were studied. The best flotation desulfurization conditions were grinding fineness of 75%, pH of 8.5, and collector of 600 g/t. “One coarse, one cleaning and one sweep” closed-circuit flotation was established as the industrial flotation desulfurization process. After the closed circuit test, the sulfur content of aluminum concentrate with the yield of 93% was 0.23%, and the sulfur removal rate was 83.16%, and the sulfur content of tailings (sulfur concentrate) was 15.09%. Keywords：High-sulfur bauxite under coal mines, flotation, desulfurization

Jan 1, 2020

OFS Branch Proceedings of the Annual General Meeting ofthe O.F.S. Branch on Wednesday, 31st July, 1974. The Annual General Meeting of the Branch was held at the Western Holdings Limited Canteen on Wednesday, 31st July, 1974 at 7.30 p.m. Mr E. T. Wilson (Chairman) was in the Chair. There were also present: Papers of interest The following papers may be of interest to members. Education fund The Institute has recently brought into being a Fund to finance various educational projects.

Jan 5, 1974

By L. von Ketelhodt

Dual energy X-ray transmission (DE-XRT) sorting is a recent development in the range of sensor-based sorting technologies available today. DE-XRT is particularly suitable for dry coarse coal beneficiation in the size range -120 mm +12 mm. In this paper, we describe the technology and show the results of a number of test runs conducted on different types of coal from the USA and South Africa. The results have shown that DE-XRT is an effective technology not only for deshaling of coal and removing pyritic sulphur but also for separating coal and torbanite. The use of dry deshaling methods will be more important as water availability becomes a greater concern. DE-XRT is one such technology which will be incorporated in future dry coal processing plants.

Jan 1, 2010

By J. Zhang, A. J. S. Spearing, L. Ma

Ore deposits are becoming more complex to mine as a result of the exhaustion of surface and other easily mined deposits. There is also increasing socio-political pressure to design more environmentally sound, sustainable, and safe mining practices. Wang and Ma designed a mining method for coal, similar to a modified drift and fill using a continuous miner to take sequential cuts (rooms) that are subsequently backfilled. The authors have modified the concept to make it more autonomous, safer, and less costly using highwall coal mining techniques, modified and adapted for underground applications. The method is more flexible than longwall mining and the percentage extraction would seem to be in the same range. In addition because of the backfilling, surface subsidence would not be a major issue and could be more effectively managed.

Feb 2, 2021

By C. Montoya

This paper shows, through a case study, the impact of multivariate grade modelling upon mine design and mine planning. A deposit explored by drill holes is considered, in which the grades of five elements (copper, silver, molybdenum, arsenic, and antimony) are of interest. Forty alternative models of the deposit are constructed by fitting the joint correlation structure of the grade variables and using conditional cosimulation. In addition, a reference model, obtained by averaging the alternative models, is also considered. The study shows that the resulting mine design (final pit characteristics and production schedules) is sensitive to the grade model under consideration, and that the design based on the reference model may not be optimal when compared to the alternative models based on cosimulation. However, when assuming a given long-term plan and extraction sequence, the grades and net present value (NPV) calculated on the reference model are unbiased with respect to those calculated on the alternative models with the same extraction sequence. The latter allow assessing the possible dispersion of the actual grades and NPV around their expected values, and are useful for the planner in order to determine the probability of meeting given production targets and of exceeding or falling short of given threshold grades. Additionally, unlike cosimulation, the separate simulation of each grade variable leads to unrealistic resource models and to biased results in mine design and mine planning. This approach should therefore be avoided, unless the grade variables are spatially uncorrelated.

Jan 1, 2012

By F. Ntuli, T. V. Nyangadzayi

Chromium green is an essential metal with various applications in the paints, construction, electronics, and aerospace industries. The main source of chromium green is the carbo-thermic reduction of chromite ores, however, chromite ores are being heavily depleted on a global scale, hence the need to find alternative or secondary sources for the chromium. In order to meet the global demand for chromium there is a need to implement principles of the sustainable circular economy to keep chromium within the material loop. Ferrochrome slag and stainless steel slags are secondary resources that are potential sources of chromium. In this work, recovery of chromium from ferrochrome slag was investigated. The ferrochrome slag was alkaline leached using sodium hydroxide- sodium hypochlorite solution to reduce the use of potent reagents that have a potential negative environmental impact. The leachate produced by oxidative alkaline leaching of ferrochrome slag contained hexavalent chromium, which was used to recover the extracted chromium through a two-stage process involving reduction and precipitation. Reduction of hexavalent Cr to trivalent Cr was investigated using anhydrous FeSO4 at concentrations of 5 g/L, 10 g/L, and 15 g/L. Precipitation was conducted by dosing the reduced leach solution with 1 M sodium hydroxide at dosages of 5 ml/L, 10 ml/L, and 15 ml/L. The experiments were designed using the Taguchi (L9) orthogonal array and analysed according to the ANOVA, general linear model. The optimized conditions for the reduction step were ferrous sulfate dosage of 5 g/L with a pH of 12, and for the precipitation step, 1 M sodium hydroxide at a dosage of 15 ml/L with a setting time of 90 minutes and pH of 7. Physical changes were observed during the two-step chromium recovery, with solution changing from a yellowish colour to dark green colour indicating completion of the reaction. The chromium recovery was found to be 93.3%.

Dec 11, 2024

By R. V. Peche

Since 1952, Bond’s equation has been used as a standard to predict the specific energy of grinding for a given duty. The Bond’s equation considers that the exponent is constant for all conditions. Hukki, in 1961, pointed out that the exponent is a function of the particle size, and concluded that the Bond’s equation applies successfully for an intermediate range of sizes; out of this range the Bond’s equation leads to high error as demonstrated in this paper. More recently, in 2004, S. Morrell presented a new formula in which the exponents vary with the feed and product size. This paper is based on Hukki’s approach and presents a new general formula, in which the exponent varies only with the feed particle size. This new equation has been proven in 82 observable cases in Peru and other countries around the world, involving ball mills and vertimills in different configurations over a wide range of feed and product sizes, work indices and mill diameters; in most cases, the predicted value has an error less than 10% with regards to the observed value and no need for any correction factor. Keywords: Grinding, specific energy, particle size, work index, variable exponent

Jan 1, 2020

By T. Mapeta, S. M. Rupprecht

Discussions on reasonable prospects for eventual economic extraction (RPEEE) include the CRIRSCO 2019 reporting template, JORC 2012, SAMREC 2016, CIM 2019 Guideline, and Regulation SK-1300. These reporting codes all conform to the principles of reasonable prospects for eventual economic extraction. To demonstrate that all mineral resources align with the RPEEE principles, the Competent Person is responsible for endorsing the mineral resource estimate. Moreover, establishing mineral resources and RPEEE requires technical input from numerous technical specialists, such as mining and geotechnical engineers, metallurgical engineers, social and environmental specialists, financial and governmental practitioners, and more. The aim is to improve the transparency of the disclosure of mineral resources and guarantee the investor or potential investor that the reporting of mineral resources is based on reliable technical, economic, environmental, social, and other relevant factors. This paper discusses the important protocols and definitions in some international reporting codes for the purposes of developing a guide memoire that will assist the Competent Person to interpret, establish and apply RPEEE appropriately and easily.

Jun 27, 2025

By R. Castro, R. Gómez, F. Betancourt, M. Moncada

In block cave mining, rock fragmentation is a key parameter that influences the production level design and mine planning. Fragmentation occurs mainly by natural breakage during the caving process and in the draw column. The breakage that occurs within the column is known as secondary fragmentation. Secondary fragmentation has been successfully described using the block caving comminution model, which replicates the fragmentation mechanics between particles under drawn and vertical loads in a draw column. This model is based on a kinetic and population balance approach, in which non-normalized and normalized assumptions can be used depending on material and comminution system behaviour. In this paper, the non-normalized and normalized approaches are applied and compared to laboratory data to determine which assumption should be used for secondary breakage in block caving. Approaches are compared graphically, with the mean square error and the Fisher test with a false-rejection probability of 0.05. Based on a statistical analysis, the results show that the normalized model can be applied to all the rock types tested.

Nov 1, 2021

By T. Scheldt, M. Lu, A. Myrvang

Abstract: In this paper both continuous and discontinuous modelling are utilised in order to analyze the stability of the Gjøvik Olympic Mountain Hall. The large span cavern (62 m) was built for the 1994 Winter Olympic Games at Lillehammer, and is a unique case study because of the large amount of available input data, through a comprehensive pre-investigation, stress and deformation monitoring program before, during and after the excavation. Phase2, a two-dimensional non-linear finite element program, and the Discontinuous Deformation Analysis (DDA) are used as representative tools for continuous and discontinuous modelling, respectively. The analysis results are compared and discussed taking the reliability of the models, time-consumption and costs into consideration. Some guidelines for the total modelling process, from field measurements to final results, are also presented. Zusammenfassung: In diesem Artikel werden sowohl kontinuierlich als auch diskontinuierlich Modellierung verwendet, um die Stabilität, der in den Berg gebauten Olympiahalle in Gjøvik zu analysieren. Die Olympiahalle wurde 1994 zu den Olympische Spielen in Lillehammer errichtet. Ihr Dach erstreckt sich über eine Breite von zweiundsechzig Meter. Für den Bau wurden umfangreiche Daten durch Voruntersuchungen, und Überwachung von Gebirgsspannungen und Deformationen bevor, während und nach Exkavation eingesammelt. Auf Grund dieser großen Datenmenge stellt die Olympiahalle ein herausragendes Beispiel für den Bau ähnlicher Projekte dar. Für die kontinuierlichen Modellierungen wurde „Phase2“, ein zwei-dimensionales, nicht lineares „endlich Element“ Rechnerprogramm angewandt. Die diskontinuierlichen Modellierungen erstellte man mit Hilfe von der „Diskontinuierliche Deformations Analyse“ (DDA). Die Analysenergebnisse sind mit Rücksicht auf die Zuverlässigkeit der Modelle, Zeitverbrauch und Kosten verglichen und diskutiert worden. Im Artikel werden Richtlinien für den Modellierungsprozess von Dateneinsammlung bis Schlussfolgerung gegeben. Résumé: Dans cet article la modélisation continue et discontinue sont utilisés pour analyser la stabilité de Gjøvik Olympic Mountain Hall. Cette caverne de grande portée (62 m) a été construite pour les Jeux Olympiques d’Hiver de 1994 à Lillehammer, et est une étude de cas unique grâce à la grande quantité de données disponibles, de par un programme de pré-investigation compréhensive, monitorage des contraintes et déformations avant, pendant et après l'excavation. Phase2, un code d’éléments finis non linéaire à deux dimensions, et l’Analyse en Déformations Discontinues (DDA) sont utilisés comme outils représentatifs de la modélisation continue et discontinue, respectivement. Les résultats d'analyses sont comparés et sont discutés, prenant en compte la fiabilité des modèles, la consommation en temps de calcul et les coûts. Quelques indications pour le procédé total de modélisation, des mesures sur place aux résultats finaux, sont aussi présentées.

Jan 1, 2003

By M. C. Bekker, T. Govindasamy

The potential benefits of implementing the Last Planner System (LPS) on mining infrastructure projects were explored through two case studies in the South African mining industry. The first part of the study involved measurement of the impact of LPS through earned value techniques on secondary project data. The second part sought to establish the lean construction success factors leading to improvements in construction performance. This was done by means of a research questionnaire distributed to the project owner’s teams, contracted parties, and the LPS facilitators. The results revealed a positive correlation between LPS application and planned percentage complete. However, the performance achieved during the LPS pilot was not sustained. The success factors and benefits considered most evident in the case study pilot differed among the three stakeholder groups. The findings are expected to guide construction stakeholders to better define performance measures and focus on factors required to make LPS implementation more effective in the South African mining sector.

Feb 12, 2024

By Nelson Sánchez

The Los Bronces Development Project (LBDP) was approved in October 2007 by the Anglo American plc Board at a capital cost of some US$1.74B, and is scheduled to be completed by the end of 2010. The project represents a big step forward for the Los Bronces mine since it will increase the treatment rate by 140%, the mining rate by 64% and almost double copper production during the first four years of the project. This economy of scale will also position Los Bronces as a much bigger and efficient mining operation, better prepared to face adverse market scenarios and allowing Anglo to consolidate its position in base metals. The project addressed numerous scope alternatives such as plant capacity vs mine capacity, cut-off grade strategy to maximise value based on the existing flotation and leaching process, cutback strategy, etc. Main infrastructure aspects of the project are as follows: ?Dump area with 2400Mt capacity for waste and low grade material ?Mining equipment: 1 x electric shovel, 12 x 300t trucks, 1 x drill ?Primary crusher: 60? x 89? ?Three new power lines (144MW capacity) ?Grinding plant at 87kt/day nominal capacity (includes a 4.3km tunnel with a regenerative conveyor belt) ?Grinding plant: 1 SAG mill 40? x 25?, 2 ball mills ?Slurry pipeline (52 km from grinding to flotation plant) with five choke stations ?Flotation plant (rougher, cleaning, regrinding circuits and molybdenum flotation). The history of Los Bronces started in 1867 when it was discovered. In 1978 ENAMI (Government company) sold Los Bronces to Exxon for US$112M. The same year a snow avalanche destroyed San Francisco Flotation Plant. In 1979 the plant was rebuilt at 4.9kt/day and from 1979 to 2002 several plant expansions were made up to 54kt/day capacity. In 2002 Anglo acquired Los Bronces for US$1.3B. The 2002 resource and reserve statement showed reserves at 459Mt at 1.02%CuT and resources at 780Mt at 0.80%CuT. The 2007 statement shows reserves at 1,480Mt at 0.67%CuT and resources at 1,644Mt at 0.45%CuT. Defining the size of a plant expansion is the key challenge that any expansionary project faces. The scope of this paper is a general review of the project, describing all the mining techniques that were used to define the best options that maximise value. In this context, a range of plant capacities (from 58 to 230kt/day) combined with a range of mining capacities (from 83 to 166Mt/a) were evaluated in detail, defining for each option a mine plan, Capex and Opex, and cut-off grade strategy for flotation and leaching processes and the associated Net Present Value (NPV) that was used as the selection criteria. The Los Bronces mineral resources potential provides good growth opportunities for the mine beyond LBDP implementation, offering an exciting invitation to continue studying new initiatives that maximise the value of this deposit.

Jan 1, 2008

By Z. Zhang, J. Niu, H. Wang, Y. Xu, J. Shi

Tribo-electrostatic separation is a promising method for effectively utiliing low-grade magnesite resources by removing quartz and improving the grade of magnesite. To determine the chargeto- mass ratios of pure magnesite and quartz, a triboelectric measurement system was employed, and a laboratory tribo-electrostatic separation system was used to separate low-grade magnesite. The results showed that the maximum difference in charge-to-mass ratio between pure magnesite and quartz particles was observed after friction with polyvinyl chloride. The grade and recovery of magnesite increased with temperature and initially increased with increasing voltage, feed rate, and air flowrate before gradually decreasing. The optimal conditions resulted in a concentrate with 46.91% MgO content and 77.36% recovery, while the quartz content decreased from 7.02% to 1.95%. These experimental results demonstrate the effectiveness and potential of tribo-electrostatic separation in removing quartz and upgrading magnesite.

Apr 14, 2024

By T. Feroze, B. Genc

"The effect of some of the system variables in forcing and exhausting ducted fan systems on ventilation in an empty heading was investigated using computational fluid dynamics(CFD) and comparative analyses. The diameter of the duct, duct mouth to face distance, and the power of the fan (quantity delivered by the fan) were varied and their effect on ventilation determined through a comparative analysis of the flow rates calculated close to the face of the heading. Estimation models were developed, which can be used to calculate the flow rate close to the face of the empty heading for different settings of the system variables studied.The study showed that recirculation for a forcing ducted fan system can be reduced by increasing the duct diameter or increasing the duct mouth to face distance. For the exhausting ducted fan system, higher flow rates were achieved by reducing the duct mouth to face distance, andincreasing the fan design flow rate and duct diameter.The outcomes of this investigation will help ventilation engineers in deciding the optimum duct fan system required for sufficient ventilation.IntroductionThe ventilation of underground mines, irrespective of the type of mine and mining method, is divided into two broad branches, the primary ventilation and secondary or auxiliary ventilation. The primary ventilation is responsible for the total volumetric flow through the mine and the auxiliary ventilation is responsible for the ventilation of the development ends, production areas, and facilities disconnected from the main circuit with no through-ventilation connections. Auxiliary ventilation is the more difficult to achieve (Bise, 1996), and the disruption of this ventilation system is considered to be one of the primary factors contributing to methane and coal dust explosions (Creedy, 1996). A number of causalities have been recorded by many authors due to these explosions (Phillips and Brandt, 1995; Dubinski et al., 2011; Phillips, 2015). The ventilation of short headings, less than 10 m in depth, can be carried out without the use of any auxiliary equipment (Feroze and Phillips, 2015). However, for headings deeper than 10 m, auxiliary ventilation systems are required. These are generally classified into the three basic types, namely line brattice (LB) ventilation systems, ducted fan systems, and jet fans (Figures 1 through Figure 3 respectively)."

Jan 1, 2017

By L. M. Tavares, H. A. Petit, P. P. Cavalcanti

Iron ore pellets experience degradation during handling due low energy impacts and stresses. These impacts lead to volume or surface breakage of the pellets, creating fine particles that accumulate along the process. Some of the particles are in contact with the air and are dragged as dust into the workplace or into the atmosphere. The aerodynamic size of the particles allows them to be potentially inhaled by the workers or to be carried to nearby communities. Dust emission becomes critical at specific locations, such as transfer chutes and stockpiles. This work models the dust generation that occurs in an iron ore pellet stockyard using a methodology that combines experiments to quantify the degradation of the pellets to mathematical modelling of the dust emission mechanisms in the stockyard. First, laboratory tests were used to characterise the amount of mass and the particle size distribution of the dust generated by degradation under controlled conditions. Second, the flow over a stockpile of an iron ore pellet company was simulated with the aid of computational fluid dynamics (CFD) simulations. Third, semiempirical equations linked the data generated by simulations and laboratory tests to estimate the dust emission in the stockyard. Finally, results were validated with measured field data, obtained with a novel online measurement tool. Results suggest that the approach is able to predict dust emission with sufficient accuracy and can be used for further implementation in the management of operations and decision making in order to reduce the environmental impact of the process. Keywords: Iron ore pellets, abrasion, dust emission, mathematical modelling

Jan 1, 2020

By V. Sheikhzadeh, M. Saghaeian, N. Esmaeili, R. Hejazi, A. D. Ahmadabadi

The main challenges in most low grade iron ore deposits are finding the optimum flowsheet for beneficiation to achieve a final concentrate from both technical and economic viewpoints. Dry preconcentration techniques are being used to assist in reducing the amount of ROM feed to the plant. In this paper the benefits of utilising a dry cobbing magnetic separation technique for upgrading the product of HPGR in a closed circuit with dry screen 4 and 1.4 mm by performing a pilot scale test work was investigated. The experimental test work was done on two sample types of Yogi BIF magnetite iron ore located in Western Australia. Prior to magnetic separation studies, detailed characterisation of the feed materials including physical, chemical, mineralogical and magnetic properties were carried out. Furthermore, the effects of process parameters: drum rotation speed (1.5, 2.5 and 3.5 m/s), magnetic field intensity (1100 and 3800 gauss) and feed size (minus 4 and 1.4 mm) were investigated. The results revealed that sample type1 with 33.90% Fe could be upgraded to 41.51% Fe by using a stage of 1100 gauss dry magnetic separator with 69.12% weight recovery and 84.36% Fe recovery at a size of 4 mm. Also for sample type2, it is possible to increase Fe grade from 29.84% to above 36.68% with 75.58% weight recovery and 90.32% Fe recovery by applying one stage of 1100 gauss dry magnetic separator to a 4 mm size sample. Keywords: Banded iron formation (BIF), pre-concentration, dry cobbing technique, magnetic separator

Jan 1, 2020

By A. M. Bauristhene

Ti-64, which accounts for more than 50% of the worldwide titanium tonnage, has found commercial importance in industries requiring components with high specific strength and resistance to corrosion. Investment casting is the preferred production method due to the difficult machinability of the alloy. This study was aimed at investigating the mechanism and the extent of alpha case formation on Ti-64 components cast using the investment casting method with YFSZ (yttria fully-stabilized zirconia) shell moulds after vacuum induction melting. The extent of the reaction between the mould hot face and the molten metal has been studied by varying parameters such as soaking temperature and mould hot face composition, and examining their effects on the reaction with the mould. An increase in the soaking temperature had an effect on the alpha case, both in appearance and hardness, but had no effect on contamination levels by carbon, oxygen, and nitrogen. The depth of alpha case increased with soaking temperature, increasing from 35 µm to 161 µm with an increase in temperature from 1200°C to 1400°C. The micro-hardness profiles provided insight into the effect of the alpha case on the mechanical properties of the Ti-64 alloy by displaying hardness values of 1000 HV0.1 and above, but could not be solely utilized to determine the alpha case penetration depth due to microstructural differences in the unaffected Ti-64, in particular the martensitic microstructure that formed with a fast cooling rate from a higher temperature. Levels of expected contaminants such as Zr, Y, 0, and C were low. The addition of the colloidal zirconia binder affected the interfacial reactions. YFSZ proved to be a thermodynamically stable refractory material, with the alpha case possibly forming as a result of segregation.

Jan 1, 2013