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By R. C. M. van der Spuy

The heavy-minerals plant at the Palabora Mining Company treats 25 to 30 kt of new feed daily. The U3Og value of the ore averages approximately 40 p.p.m. The circuit consists of four stages of upgrading on 68 Reichert cones, fol. lowed by a jig and 30 table decks. The paper describes how feed-distribution problems have been overcome and the methods used for monitoring and controlling the cone performance. The adaptation of a standard jig for the recovery of fine minerals is discussed, and a method of 'table agglomeration, for the recovery of coarse refractory copper sulphide is described. The tables consist of polyurethane-covered fibreglass decks, and their operation is controlled according to measurements of the uranothorianite content of the concentrates and middlings by means of a nuclear scintillation counter. The upgrading ratio of the uranium mineral by gravity concentration is 1000:I, baddeleyite (ZrO.) being recovered as a by product.

Jan 1, 1982

By F. Riedel

In May 2009 a test work programme was carried out at the sorting laboratory of CommodasUltrasort in Germany which was aimed at establishing the efficiency of X- ray transmission sorting for the recovery of unliberated diamonds in a size range of +8mm. A PRO Tertiary XRT belt sorter with a working width of 600mm and a belt speed of -3mJs was used for the test work. Dual energy X-ray transmission sorting is a type of sensor-based sorting which uses an X-ray scanning system, The attenuation of the transmitting X-rays is measured at two different energy levels, Thereby it is possible to eliminate the effect of the particle thickness on the measurement result. The effective measurement results in a classification by elemental order based on the periodic table.

Jan 1, 2010

By D. Botha, J. F. Cronjé

"SynopsisAlthough women all over the world have been involved in mining activities for centuries, mining has always been considered a very masculine industry due to its heavily male-dominated workforce as well as the physicality of mining work. The mining industry has not been an obvious career choice and preferred place of employment for women; women were mainly employed in administrative and advisory positions. Until 1994, women were legislatively prohibited from being employed in underground operations in South Africa, but the Mines Health and Safety Act, No. 29 of 1996, removed these restrictions. In addition, new mining legislation (the Mineral and Petroleum Resources Development Act, No. 28 of 2002) and the accompanying Mining Charter make specific provisions for the inclusion of women in core mining activities and require 10% of core positions to be filled by women.This article voices perceptions of the physical ability of women employed in core mining positions. Findings are drawn from empirical work undertaken at platinum, phosphate, and copper mines. Quantitative and qualitative research paradigms are used. It is evident that women find it extremely difficult to perform mine work that requires physical strength and stamina. Practical recommendations, informed by the literature review and empirical findings, are made with the objective of contributing to the sustainable deployment of women in the mining industry.IntroductionFor many years, mining has been considered the foundation of the South African economy. Although the mining industry in South Africa is currently under considerable pressure and experiences various challenges, including escalating operational costs, electricity tariff increases, safety-related issues and associated production stoppages, poor productivity, labour unrest, and reduced demand both globally and domestically, it remains a key contributor to the national economy and development of the country (IDC, 2013, p. 9).Until 1994, women were legislatively prohibited from meaningful participation in the mining industry and were denied access to skills and jobs, self-employment, and entrepreneurship. The newly elected democratic government in 1994 initiated substantial socio-political and economic transformation in South Africa. Nearly every sector in the country was transformed and re-shaped, primarily through sector-specific legislation, but also through negotiations between government, industry, and labour unions to create and refine the so-called sector charters, which included the Mining Charter. The vision of the new regime, the African National Congress (ANC), was to ‘transfer power to the people and transform society into a non-racial, non-sexist, united, democratic one, and change the manner in which wealth is shared, in order to benefit all the people’ (ANC, 2007)."

Jan 1, 2015

By E. Rex, T. J. Goff, W. S. B. van Beek, P. E. Nel

"The PGM smelting industry is known for operating at significant high superheats. Both the slag and matte phases that separate via gravity need to be tapped out of the furnace in a safe and efficient manner, which can be achieved only through sound tap-hole management practices. This paper gives an overview of the tap-hole management approach followed in the operations at Lonmin’s Western Platinum Smelter.Five circular AC furnaces are operated, with each furnace comprising essentially a crucible and auxiliary equipment. Within the crucible, slag and matte tap-holes are situated at different elevations. The slag phase is tapped at a higher elevation than the matte phase. At the three older furnaces, tapping is done by the conventional method of lancing open the tap-hole and closing it with a dolly. However, at the two newer furnaces, tap-holes are opened and closed with the aid of a drill and mudgun.Tap-hole management can be divided in a number of aspects. In order to achieve a safe opening and closure every time, Lonmin distinguishes between three important aspects - the design of the tap-hole system, the operating practices followed, as well as care and maintenance. This paper briefly describes the tapping channel and cooling requirements for handling superheated matte, together with the difference in design of the matte and slag tap-holes. Mention is also made of the importance of auxiliary equipment, which includes the launders, fume extraction, granulation water, and mudgun and drill units. Improvements made to the matte tapblock design are discussed.The monitoring, alarm, and safety systems related to matte and slag tapping are described. Tap-hole life and different wear mechanisms are mentioned. Tapping can be done safely only if the tap-holes and equipment are maintained properly. Mention is made of the tap-hole refractory repair practices, and the improvements made in order to reduce repair time as well as to extend the time between deep repairs. The importance of the correct tap-hole clay selection in order to nurse the tapping channel after each tap is also discussed.The paper finally touches on some research and development work that was done in order to improve the monitoring of the condition of the tapblock by means of fibre optic temperature sensors"

Jan 1, 2014

By G. T. C. Emere, E. C. Hunter

The use of cylindro-conical settlers for the clarification of underground water by E. C. HUNTER- (Associate) G. T. C. EMERE-, B.A. (Hons.) (Keele) (Visitor) This paper analyses the performance of conical settlers on Harmony Gold Mine from 1959 to the present time, and describes the investigation that was undertaken to substantiate and improve the use of conical settlers for a new pump chamber in another part of the mine.

Jan 5, 1977

By J. H. Potgieter

This paper describes two cases of corrosion that occurred in dry-process, rotary, cement-clinker kilns. In the case of the kiln with five pre-heater stages, the attack occurred primarily from sulphates that probably originated in the raw feed and fuel being used in the plant and that penetrated the refractory lining. The corrosion was similar to ash-deposit corrosion often observed in steam boilers. In the second case the plant consisted of a long dry kiln with a single pre-heater fitted to the feed-end. In this case the corrosion could be ascribed to alkali chloride penetration through the refractory-brick lining and subsequent hot corrosion of the kiln shell.

Jan 1, 2004

By F. Yang, T. Pan, T. Zhao, Z. Shao, D. Zuo

In this paper, the development and applications of robot technique is summarized, and the status and developing direction of China coal mine robotics. A description of the research meaning, frame and key technology of underground salvage robot is given. Keywords: coal mine, robot, special robot, salvage robot.

Jan 1, 2003

By H. S. Eisner, J. -P. Leger

Published South African fatality and injury statistics for mine accidents are investigated. Where possible, the South African statistics are compared with those of other countries. Commonly held attitudes to the South African accident experience are also examined. Analysis reveals that the published accident rates present a more favourable picture than the rates actually experienced by underground workers. In addition, fatality rates in South African underground gold and coal mines do not differ significantly and have remained stable over the past decade, although the injury rates have decreased rapidly. No evidence was found that this is due to improved safety, and a comparison with international fatality and injury data suggests that it is not. The underground fatality rate for South African coal mining is, on average, eight times that of the UK, four times that of all EEC coal mines taken together, and over double that of the USA. Despite the unreliability of the injury rates, much has been made in South Africa of their rapid decline, an emphasis that appears to be misplaced.

Jan 1, 1988

Many industries base their decisions on the assaying of tiny analytical sub-samples. The problem is that most of the time several sampling and sub-sampling stages are required before the laboratory provides its ultimate assays using advanced chemical and physical methods of analysis. As long as each sampling and sub-sampling stage is the object of due diligence using the Theory of Sampling it is likely that the integrity of the sought after information has not been altered and the generated database is still capable to fulfil its informative mission. Unfortunately, more often than not, unawareness of the basic properties of heterogeneous materials combined with the unawareness of stringent requirements listed in the theory of sampling, lead to the conclusion that massive discrepancies may be observed between the expensive outcome of a long chain of sampling and analytical custody, and reality. There are no areas that are more vulnerable to such misfortune than sampling and assaying for trace amounts of constituents of interest in the environment, in high purity materials, in precious metals exploration, food chain, chemicals and pharmaceutical products. Without the preventive suggestions of the theory of sampling serious difficulties may arise when making Gaussian approximations or even log-normal manipulations in the subsequent interpretations. A complementary understanding of Poisson processes injected in the theory of sampling may greatly help the practitioner understand structural sampling problems and prevent unfortunate mistakes from being repeated over and over until a crisis is reached. This paper presents an overview of the theoretical, practical and economic difficulties often vastly underestimated in the search for quantifying trace amounts of valuable or unwelcome components.

Jan 1, 2009

By A. V. Pavlov, V. A. Grygorian, Kossyrev, A. E. Semin, A. Korostylev

A new way of producing low-silicon ferrosilicon from iron-ore materials in a new type of aggregate-oxygen reactor is presented. The oxygen reactor process is based on using the calorific combustibility and reducibility of carbon materials inside the aggregate. The key to the process is successful post-combustion of carbon monoxide above a layer of a solid coke bed. Initially the possibility of production of grades of ferrosilicon containing 20 to 25% Si (FeSi20-FeSi25) was studied on a laboratory model of the oxygen reactor. Quartz sand and iron ore concentrates (from Russia and India) were used in the laboratory tests. This test work demonstrated that a ferrosilicon grade FeSi15 could be obtained directly from raw iron ore (containing 75.9 % Fe2O3 and a maximum of 23.8 % SiO2) without using rich iron-ore concentrates. The process was successfully tested on a pilot furnace at Serovsky metallurgical plant. Very promising results and efficiency parameters were achieved. The consumption of materials for 1t of ferrosilicon (15 % Si) production was as follows: 1567 kg raw iron ore, 591 kg of coal (in a composition of ore-coal briquettes), 299 kg of coke (for coke bed formation), and 815 m3 of oxygen.

Jan 1, 2004

By D. M. MacHunter, T. Lawson, D. K. Henderson

The development and commercialization of new generation high tension electrostatic separators has provided a basis for simplifying mineral separation plant circuitry. The inclusion of new design features including insulated plate electrodes that have resulted insignificantly improved separation efficiencies in electrostatic separators are described. The increase in separation efficiency has resulted in a reduction in the number of treatment stages required to produce final high grade mineral products. Comparative performance data on different feed types are presented. A comparison between mineral separation plant flowsheets using both conventional and new generation high tension electrostatic separation technology is presented. A 55% reduction in the number of installed electrostatic separators and a 36% reduction in plant area was achieved through the use of this new electrostatic separation technology.

Jan 1, 2003

By M. K. G. Vermaak

Spiral concentration forms a crucial part of gravity separation circuits. The application of process models in the operation of gravity separation circuits offers significant benefits in recoveries and grade control. Significant strides in the modelling of spiral concentrators have been made during the last couple of decades. Despite these advances in modelling techniques and models, application in industrial processes is not fully optimized. The adjustment of splitter positions to accommodate changes in the feed parameters is impractical and difficult, resulting in losses. In this work an optical method is employed to detect the concentrate band position as a function of operating variables. As expected, the results indicate a strong influence of the solids content and total heavy mineral (THM) feed grade on the predicted gangue-mineral interface. Viscosity modifiers indicated the band position to be sensitive to viscosity and therefore the slimes content. Validation on an industrial sample indicated the possibility of using this model in feed-forward control application.

Jan 1, 2008

By M. Yavuz, M. Aksoy, G. Once, M. Iphar

This paper is concerned with a study on the floor heaving in the transport road of the GLI Omerler Colliery in Tuncbilek-Turkey. This gallery has been opened at the depth of 200 m through the formation of marl in 4.6 m width and 3.5 m height in cross section. Floor heaving occurred up to 70 cm in height in maximum and caused severe problems in railway and band-conveyor transportation in the main road. In addition; after the current panel mined out, the shield support units could not be transferred to the new panel because of the deformation of roadway cross-section. The I-profile steel arch supports also sank into the weak floor rock. This situation has been studied by numerical analysis using the FLAC3Dfinite difference program in order to investigate the rock mass behaviour around the opening. The obtained outputs of the numerical model have showed consistency with the amount of floor heaving in the gallery at 200 m depth. A new gallery has been driven at the depth of 115 m and M4 longwall panel has just been taken to production. So as not to encounter with the same problems at 200 m depth, especially longwall face moving problem, various numerical models have been studied in order to keep the floor heaving in the acceptable limits required to move shield support units. Keywords: Floor heave, Numerical modelling, FLAC3D, Failure criteria, RocLab

Jan 1, 2003

By B. M. Loftus

An investigation into the use of impinging stream (jet) reactors for the leaching of a free milling ore produced an increase in gold recovery by 10% while decreasing leaching time by up to 90%.Tests on refractory ores demonstrate no apparent improvement in recovery. However, leaching kinetics are dramatically increased when these ores are subjected to jet reaction prior to agitation.

Jan 1, 1997

By E. Wolmarans

Dowding, Reynard and Associates Mineral Projects (DRAMP) was approached by the ARM/Lion Ore JV during July 2006 to conduct a feasibility study and control budget estimate for a new greenfield project for their NKOMATI Nickel mine 45 km east of Machadadorp. The scope included the evaluation and review of previous studies as well as a techno-economic trade-off on four possible comminution circuits ranging from conventional crushing and ball milling to fully autogenous milling. The following document encapsulates the thought process, decisions and the references used in selecting the final comminution route for the new 375 ktpm MMZ concentrator. Apart from the pilot test work performed, design simulations from a number of sources, performance results from a recently commissioned 100 ktpm MMZ concentrator, together with an understanding of the geology and mineralogy of the orebody and possible variations in the characteristics of the orebody over the life of mine were assessed. The results from all the above-mentioned work indicated that it would be possible to treat the MMZ ore at the desired throughputs to the desired grind sizes in a fully autogenous grinding (ABC-type) circuit. Autogenous milling is generally considered to be one of the higher risk milling circuits. This is mainly due to the fact that the ore, which is utilized as the grinding media, could be variable in terms of hardness and mineralogy/geology. Nevertheless, it is a very popular route as the cost benefits, more specifically the operating cost, are normally very attractive. This is especially the case when large low grade orebodies are evaluated. In North/South America, autogenous and semi-autogenous grinding circuits have been successfully employed during the past 20 years on large scale low grade operations. Taking all the above factors into account, the DRA/Nkomati project team recommended an autogenous circuit with the option to add steel to both the primary and secondary mills (if required) for the new operation in order to create the opportunity for significant operating cost savings. One has to bear in mind that all the new design simulations and decisions are based on previous work and potential unknown variations within the orebody will never be fully understood until the pit is operational for some time.

Jan 1, 2009

By G. A. Bezuidenhout, J. P. T. Kapusta, D. K. Chibwe

"Peirce-Smith converters (PSCs) are extensively used in the copper, nickel, and platinum group metals industries to remove iron and sulphur from the molten matte phase. This technology has not changed significantly since its inception in the early 20th century. The typical converting operation involves lateral purging of air/oxygen-enriched air into molten matte through a bank of tuyeres. This blowing operation occurs at low air pressure from the blowers, and the induced bubbling regime is considered inefficient from both a process and an energy utilization perspective. Inherent drawbacks include recurrent tuyere blockage, inevitable tuyere punching operation to clear airways, and low oxygen efficiency as a result of substantial air losses due to leakages.Investigations in the 1980s demonstrated1 that jetting into Cu and Ni converters could reduce or eliminate some of the process difficulties. In spite of these findings, very little progress has been made in the application of these concepts for converting of non-ferrous melts on a commercial scale.As part of its operational improvement and energy reduction initiative, Western Platinum embarked on a full-scale industrial evaluation of generating a jetting regime by using sonic injection. Prior to full-scale industrial evaluation, a numerical assessment was conducted to ascertain the feasibility of implementing sonic injection on Lonmin converters. The work included flow characterization at high injection pressures achieving sonic velocity at the tuyere exit. The 2D and 3D simulations of the three-phase system were carried out using the volume of fluid (VOF) and realizable k- e turbulence models to account for the multiphase and turbulence nature of the flow, respectively. These models were applied using the commercial CFD numerical code FLUENT.This paper discusses the key findings regard ing understanding of gas plume extension, velocity distribution, shear wall stress analysis, and phase distribution characteristics in the system. Plant trials are also discussed with reference to the commercial aspects of a fullscale implementation of sonic injection in the smelter."

Jan 1, 2014

"Sampling error and bias, especially the Increment Preparation Error (IPE), are introduced when the tool allocated to do the job fails to extract a representative sample. This is the case with chip sampling; the tool can only extract haphazard shapes of loose or fractured material and not always from within the demarcated sample area. Increment Extraction Error (IEE) and Increment Delimitation Error (IDE) could be severe, but are found to be relatively unbiased. The uncontrolled action of the sampler in discarding excess sample material after sample collection has a significant impact on the error and bias introduced with each and every extraction. A new type of bias, referred to as the ‘waste discard bias’, arises when samplers select what portion of the excess sample material to discard at the sample site. Material visually identified as waste is discarded in preference to mineralized broken ore if there is an excess of sample material. This results in a considerable error in the analytical results. The bias is proportional to the reef-waste ratio in the demarcated sample. IntroductionTwo types of ‘sampling’ are distinguished, namely sampling of particulate materials (broken ores) and sampling of solid, unbroken in situ mineralized reef. This study considers only chip- or face-sampling of in situ, goldbearing, carbon-rich conglomerates typical of the Upper Witwatersrand Supergroup and examines where components of sampling error and bias, clearly specified in the Theory of Sampling, may arise during the practice of ‘face sampling’. Many millions of face samples have been extracted from Witwatersrand-type mines using a hammer and chisel, and detailed descriptions (standard operating procedures) of how the samples should be taken have been developed by many mining companies. There is, however, no taxonomy or nomenclature for managing or reporting the different types of errors associated with chip sampling. The Theory of Sampling compiled by Pierre Gy in the early 1950s provides, comprehensive nomenclature of sampling errors that is applied to particulate sampling of ore in a lot, a stockpile, or a moving stream on a conveyor belt. The taxonomy and characteristics of sampling errors, grouped according to the sources from which they arise, and identified by Gy (1973, 1979, 1982, 1992, 1995, and 1998) are shown in Figure 1. This classification of errors is used extensively in regard to the sampling of particulate materials in the mining and minerals industry, but not in regard to chip sampling. A relatively small mass (hundreds of grams) of representative particulate material for estimating the average grade of a much larger mass (thousands of tons – the ‘lot’ in the Theory of Sampling) is extracted by the chipping or cutting of a representative rock ‘sample’ from the stope face."

Jan 1, 2016

By I. M. Macleod

An adaptive steady-state on-line optimizing regulator is proposed as an integrated approach to the control of autogenous run-of-mine milling circuits. This optimizing regulator continuously estimates an internal model of the controlled process, and, based on this, determines mill fresh solids feed rate, mill water flow rate and sump water addition flow rate such that a circuit performance objective is optimized. The dual -requirement of controlling both the mill pulp load and the load of particles of grinding media size is thus directly and simultaneously addressed. The concept and theory underlying the operation of the adaptive optimizing regulator are discussed.

Jan 1, 1987

"Pressure leaching is an option for copper recovery from chalcopyrite. Leaching takes place at high temperatures and pressures in the presence of an oxidizing agent. This work shows how the performance of pressure leaching circuits may be improved by optimizing the configuration of autoclaves and the heat removal method. The objective was achieved by creating an autoclave model that combines mass balances, energy balances, and population balances. A base case circuit consisting of a single autoclave was chosen, and this base case was compared with options for increasing capacity by adding more autoclaves to the circuit. These capacity increase options include circuits in which the additional autoclave is added in parallel, in series, and in series with thickening between the two autoclaves. The copper extraction, productivity, and cooling requirements for these options are compared. The series circuit with interstage thickening has the highest extraction and productivity; however, the cooling duty in the first autoclave is high. In addition to comparing circuit options, three options for heat removal were investigated: cooling coils, quench water, and flash recycling. The flash recycle option results in the highest copper extraction, and the quench water option the lowest copper extraction. IntroductionBackgroundCopper sulphide ores and concentrates containing chalcopyrite are typically hard to leach under atmospheric conditions. Smelting of these ores may also be a challenge, due to the inability of smelting processes to handle low-grade ores, as well as impurities such as arsenic and antimony. Alternative hydrometallurgical routes to treating chalcopyrite are therefore required. One option is pressure leaching, which is the focus of this work.In the pressure leaching process, sulphide ores and concentrates are leached in autoclaves at temperatures of 200 to 220°C and a pressure of about 3000 kPa (Schlesinger et al., 2011). An oxidizing agent, usually oxygen, is required to oxidize sulphide ions to sulphate ions. The oxidation of sulphur to sulphate is exothermic; consequently, a method of heat removal is necessary in order to maintain the temperature in the autoclave."

Jan 1, 2016

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.