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High pressure grinding roll (HPGR) technology is used in an increasingly diverse range of applications, predominantly iron ore , gold and diamonds. KHD Humboldt Wedag HPGRs are applied world-wide, and consistently prove to be well designed and reliable operating units, with their performance meeting the pre-set standards. This publication summarizes some of the features and experiences for recent applications in treatment of copper ore, coarse iron ore, and gold ore. Summary data of roll surface wear life and operating data are given, together with operational observations. In addition, effects of feed segregation and truncated feed are discussed, as well as the implications of a product recycle flow sheet.

Jan 1, 2012

By A. Kapito

The ferrite-pearlite microstructure is the most popular microstructure for alloys used in structural applications, including railway wagon wheels. These alloys have been designed through alloying and thermo-mechanical processing to have a refined microstructure. Ferrite-pearlite alloys are low cost, weldable, have good fabricability, and are reliable under extreme conditions. Given these performance attributes, it seems unlikely then that their dominant position as structural steels would ever be challenged by alternative microstructures. One major achievement in the development of ferrite-pearlite steels has been in the refinement of their interlamellar spacing to very fine distances of the order of < 0.3 µm. A refined microstructure increases the hardness of the alloy, thus increasing its life under wear conditions. The interlamellar spacing in pearlitic steels has, however, been refined almost to its theoretical limit. The increasing demand for speed and increased axle loading on railway wagons requires the use of stronger, tougher, and more durable materials. This has opened the window for the development of novel bainitic steels. Bainitic alloys have a higher level of microstructural refinement than pearlitic ones. They have shown to have good wear resistance and rolling-contact fatigue resistance, and high toughness. This paper will discuss the progress to date on the development of bainitic railway wheel alloys. Four alloy chemistries have been chosen for possible further development.

Jan 1, 2012

By D. J. Stanton

The objective of this study was to develop, install, and test a small underground mobile refrigeration plant (MRP) to deal with some of the real problems associated with mine cooling in an operating mine. The requirement for cooling the underground environment is discussed with particular emphasis on the need for this method of cooling, with the concomitant benefits. The research investigated current methods of cooling and reasons for previous failures in MRP. Both static and dynamic simulations were conducted to increase the confidence level under operating conditions. Implementation and testing, resulted in ?lessons learnt? requiring modifications, which are documented. Actual results have been recorded. These results have proved that significant cooling via MRP is feasible. Main benefits include positional efficiency, cost per kilowatt of cooling and cooling opportunities for remote hot areas of a mine. Finally, a proven technology is now available for large-scale implementation in the mining industry. Now the ventilation engineer has another system of cooling, which can be utilized in the quest to create an occupational environment, which meets the physical and mental health requirements of the worker.

Jan 1, 2004

"Coal seam gas problems can adversely affect the safety and productivity of underground coal mines, leading to fatalities and financial losses. Conventional gas management technologies using ventilation and gas drainage are unable to deal with the high and irregular gas emissions associated with high-production longwall mining. New technologies need to be developed to supplement the traditional gas management techniques to minimize the hazard of coal seam gas. Thin spray-on liners (TSLs) have gained some success for rock surface support since their introduction to the mining industry. Due to their relatively low permeability and appropriate mechanical properties, TSLs also show potential to be used as a gas management tool in underground coal mines.In this paper we review the current gas management challenges and discuss the potential use of TSLs as a gas management tool in underground coal mines. This may involve reducing gas migration into the excavations/roadways, enhancing in-seam gas drainage, and preventing spontaneous combustion. Some potential areas for future research work are identified. IntroductionWhen a coal seam is influenced by mining activities, gas stored inside is liberated into the underground ventilation system. Gas emissions have created serious difficulties for the coal mining industry around the world. Therefore, coal mines have to develop effective strategies to control the gas concentration below the threshold value to meet statutory requirements. Ventilation has been the first solution in gas management for underground coal mining. When the emitted gas cannot be effectively diluted by ventilated air, gas drainage using pre- and/or post-drainage has to be introduced. However, even with ventilation and gas drainage, irregular gas emissions usually increase the gas concentration in roadways and slow down the development rate, thus causing significant economic loss to the coal mining industry (Thakur, 2006). Therefore, new technologies need to be developed to address this issue and mitigate the explosion risk."

Jan 1, 2016

By M. Rudolph, R. Tolosana-Delgado, G. van den Boogaart, M. Reuter, U. Peuker

This paper addresses the challenge to define a concept of entropy (state of order) for a textured particle system. Both the particle texture, the intergrowth respectively, and the particle size influence the order of a particle system. The smaller the particles become, the more particles form the solid system and the more permutations of the structure of the particle bed are possible. The texture within a particle is fixed, as long as it is not subjected to changes due to comminution, flocculation or agglomeration. The paper will present a definition of entropy, which is able to reflect qualitatively and quantitatively the intergrowth and the size (distribution) of the particles. Theoretical examples will show how different breakage mechanisms can be identified using the entropy definition. Furthermore, we will define the specifications for data sets to calculate the entropy of a particle system. Keywords: Milling, mineral liberation, intergrowth, statistical entropy, modelling

Jan 1, 2020

By M. Krasowska, W. Skinner, R. K. Asamoah

Understanding chemical interactions at solid-liquid interfaces have played a pivotal role in improving mineral flotation performance, increasing the rate of mineral crystallisation and profitable leaching of valued minerals and metals. This paper highlights gold leaching with links to surface and interfacial chemical processes occurring, and opportunities to maximise extraction while reducing usage of more recent scarce resources. From the review, there is a significant link between surface and interfacial processes and gold leaching performance. Evidently, gold leaching kinetics could be increased by changing leaching conditions, including manipulating the surface and interfacial interactions. Control of surface and interfaces during gold extraction could enhance rapid, smarter gold extraction and mitigate formation of passivation layers. Keywords: Surface and interfaces, refractory ores and concentrates, gold leaching, reaction mechanism and kinetics

Jan 1, 2020

By S. A. Lorentz, Y. Xu, C. Theron

The failure of tailings storage facilities (TSFs) results in the discharge of significant quantities of hazardous waste material into the natural environment. Research studies relating to slope instability have identified physical mechanisms such as rainfall-induced erosion, liquefaction, and shear failure as the main triggers. The generation of transient pressure waves and the mobilization of pre-event water in the unsaturated zone have been found to trigger shallow landslides in natural hillslopes. In this paper we review these physical mechanisms, known as groundwater ridging (GWR) and the Lisse effect (LE), from other studies. Previous researchers have explained both these phenomena through field and laboratory observations, numerical modelling, as well as conceptual discussions. These case studies demonstrate the impact of rainfall characteristics on the generation of transient pressure waves that rapidly increase the phreatic surface and change pore water suction. Reference is also made to the influence and behaviour of physical porous medium characteristics on the establishment of a continuous water phase that facilitates the transmission of an induced pressure head. However, previous studies fail to recognize the possibility that the pressure increase in pre-event water through pore air propagation could cause slope instability in tailings dams. The authors suggest that the physical properties and hydraulic behaviour of unsaturated porous tailings media make it susceptible to GWR and the LE, resulting in the creation of a potential failure plane.

Feb 2, 2022

By K. Moxham, B. McKeown

The South African gold and platinum deposits were formed in very different ways and yet both have many similarities. They are flat dipping tabular orebodies, extremely narrow and located in hard abrasive country rock. The mining methods employed are also similar. Primary access is via shafts or declines; secondary access is via haulages and cross-cuts; and tertiary access is from raises. The proposed solution for rapid access described in this paper is focused on the haulages and cross-cuts.

Jan 1, 2006

By Z-B. Cheng, X-J. Liu

"Intensive mining of shallow coal seams tends to result in severe subsidence of the ground surface. Surface subsidence is a complex dynamic spatiotemporal process that constantly changes as mining advances. With Liangshuijing coal mine as a case study, 3DEC numerical software was used to simulate the development of the moving subsidence field from open-off cut to full subsidence on the working face. The results demonstrate that the formation of a subsidence field is directly related to the coal seam depth H and the extent of the mine workings. Taking the advance distance of the working face as the unit of scale, the process of surface subsidence can be divided into four stages: micro-change (H/ p), the development of surface subsidence (2H/ p), the formation of a movement subsidence field (3H/ p), and dynamic balance (4H/ p). The changing movement of a subsidence field can be fully described by the characteristics of surface subsidence value, curve slope, and the inflection position. The results provide important technical support for predicting surface subsidence and the temporal–spatial evolution features of mining subsidence. IntroductionChina’s coal output was about 3.52 Gt in 2017 (China National Coal Association, 2018), making it the largest coal producer in the world, accounting for almost half of total world coal production. Coal production and distribution play a vital role in the energy industry of China. However, entire overlying strata, from coal seam to surface, are disturbed as a result of long-term, high-intensity and large-scale mining, causing surface subsidence. This results in groundwater loss, surface desertification, vegetation loss, and mud-rock flows. These issues have become topics of common concern throughout society. According to related research results (Liu 2008), the area of surface subsidence caused by coal mining in China has reached about 600 000 ha, some 0.2 ha (and up to 0.42 ha) of surface subsidence for every 10 000 t of coal produced. Surface subsidence disasters not only damage buildings, water conservancy, transportation infrastructure, and farmland, but also cause adverse effects on individual and community lifestyles, environmental hygiene, and economic development. Deterioration of the ecological environment in mining areas has a long history and is very harmful (Lu, 2015)."

Feb 1, 2019

O.F.S. Branch Minutes of the Committee Meeting held in the Committee Room at the St. Helena Club at 4.45 p.m. on Wednesday, 3rd September, 1975. Book reviews JONES, M. J. (ed.). Minerals and the environment. London, Institution of Mining and Metallurgy, 1975. Mining Companies of the world.. 1974/75. London, Mining Journal Books Ltd (15 Wilson Street), 1975. £12. 303 pp. NIM reports Report no. 483 Summary of the mineralogical investigation of pegmatites. (11th April, 1969; re-issued October 1975). Report no. 1697 A petrographic and mineralogical investigation of silica samples from the farm Elandskraal 470JQ, Rustenburg district. (24th Jan., 1975; reissued October 1975). Report no. 1761 The determination, by atomicabsorption spectrophotometry, of minor elements in anode sludges and residues. Report no. 1762 The determination, by instrumental neutron-activation analysis, of some elements in the NI M ROC standard reference materials. Report no. 1770 The spectrophotometric determination of vanadium in chromiumbearing materials. Foundry conference An international foundry confcrence, spomored and organized by South African Institute of Foundrymen, will be held in Johannesburg from 23rd to 27th February, 1976. The themes for each day are follows: Coordination chemistry A symposium on coordination chemistry in extractive metallurgy is to be held in Kelvin House, Johannesburg, on 18th and 19th March, 1976. Practical jet cutting The third international symposium on jet-cutting technology to be organized by BHRA Fluid Engineering will be held in Chicago from 11th to 13th May, 1976, in conjunction with the lIT Rese:uch Institute of Chicago. Hydraulic transport The fourth international conference on the hydraulic transport of solids in pipes (Hydrotransport 4) is being organized by BHRA Fluid Engineering.

Jan 12, 1975

High pressure grinding roll (HPGR) technology is used in an increasingly diverse range of applications, predominantly iron ore, gold and diamonds. KHD Humboldt Wedag HPGRs are applied world-wide, and consistently prove to be well designed and reliable operating units, with their performance meeting the pre-set standards. This publication summarizes some of the features and experiences for recent applications in treatment of copper ore, coarse iron ore, and gold ore. Summary data of roll surface wear life and operating data are given, together with operational observations. In addition, effects of feed segregation and truncated feed are discussed, as well as the implications of a product recycle flow sheet.

Jan 1, 2012

By P. G. Terrazas Prado

This paper presents the results of research on the development and application of a custom-made truck cycle and delay automated data collection system (TCD-ADCS) in a surface coal mining. Truck cycle and delay field data are locally stored in trucks and then synchronized and replicated through a wireless network into a centralized server containing an already-developed integrated production management system (IPMS). The system relies on motion sensing and distance travelled in order to automatically define the cycle starting/ending points, cycle time, position, and delay time. Connectivity and communication between loading equipment and trucks are also established. Communication between the equipment operators and TCD-ADCS system is via a user-friendly graphic interface. The hardware used for the development of this system consists of a rugged touch-screen personal computer, 2.4 GHz radio transmitter antenna, and a commercial GPS receiver. The system was developed, tested, and deployed at a surface coal mine in the USA. Keywords surface coal mining, truck and shovel, data collection, information systems.

Nov 1, 2013

By C. S. Oteo, H. Suárez, P. de la Fuente

ABSTRACT: In the south of the Island of Gran Canaria (Spain) there appear layers of swelling clays inside volcanic formations of a fonolitic type, down to depths as low as 500 m, with thicknesses of 1 to 3 m. Two tunnels (each of length 1,500 m) have been built in these zones (ignimbrites and swelling clays), work on which started in the ‘70s. The construction has been influenced by phenomena of expansivity and decompression. Presented below are the problems that arose, the field and indoor studies conducted and the numerical optimisation of the lining. ZUSAMMENFASSUNG: Im Süden der Insel Gran Canaria (Spanien) kommen im Inneren vulkanischer Formationen phonolithischen Typs in Tiefen von bis zu 500 Metern 1 bis 3 Meter dicke Blähtonschichten vor. In diesem Gelände aus Schmelztuff und Blähton begann man zu Beginn der siebziger Jahre, zwei Tunnel von jeweils 1.500 Metern Länge anzulegen. Die Bauarbeiten standen unter dem Einfluss von Dehnungs- und Dekompressionserscheinungen. Der folgende Text enthält eine Darstellung der aufgetretenen Probleme, der durchgeführten Feld- und Laborstudien und der numerischen Optimierung der Tunnelauskleidung. RESUME: Dans le sud de l’Ille du Gran Canaria (Espagne) on a détecté des couches d’argile gonflante dans l’intérieur des formations de roches volcaniques fonolitiques, à la profondeur autom des 500 m, avec épaisseur de 1 à 3 m. On a perforé deux tunnels (de longueur 1.500 m chaque un) dans cettes zones (igniumbrités et argiles gonflantes), chantier qui comenza pendant les 70’. La construction on a influencé pour des phénomènes d’expansivité et de décompression. Dans cette communication on présente les problèmes presentes, les études de chantier et théoriques realicés et l’optimisation numérique développé pour dimensionner le revêtement.

Jan 1, 2003

By M. Pelser, J. Hagemann

"The Anglo American Platinum Rustenburg Base Metals Refiners (RBMR) is the largest producer of nickel cathode in South Africa. It treats slow-cooled matte to recover a platinum group metal-containing magnetic fraction for downstream processing and a nonmagnetic fraction to produce nickel and copper cathode, cobalt sulphate, and sodium sulphate. The refinery was recently expanded from 21 to 33 kt/a nickel. During the ramp-up phase, the sulphur removal section was found to be a constraint to throughput. Nickel hydroxide is precipitated from nickel spent electrolyte by addition of sodium hydroxide, and filtration of the nickel precipitate allows sulphur to be removed from the circuit as aqueous sodium sulphate in the filtrate. The filtration fluxes were found to be limiting the circuit’s capacity. An obvious solution would have been to install additional filtration capacity at significant capital cost and long lead times. RBMR chose rather to first initiate a collaborative project with Anglo American Technical Solutions to better understand the impact of process conditions on filtration characteristics and to evaluate whether the filtration flux could be increased by improving the quality of the nickel precipitate.A deeper understanding of nickel hydroxide precipitation chemistry and kinetics in the context of high nickel and sodium hydroxide concentrations was developed, guided by precipitation theory and confirmed by laboratory tests and plant observations. It was found that the filtration rate could be significantly improved by modifying the precipitate characteristics. A new precipitation process was engineered and retrofitted into the existing plant. Since start-up of the new precipitation system, the available capacity of the sulphur removal section has more than doubled, and control of the process has improved with the better agitation. This paper describes the theory and results used to design the new agitation system, as well as the impact of the change on capital investment, operability, and process efficiency."

Jan 1, 2016

By B.E. Hall

Maximizing shareholder value has become a common aim for mining companies. This paper discusses the results of a number of studies developing strategic mine plans, covering a wide range of commodities, styles of mineralization, mining methods, and processing facilities, for single and multiple deposits. It has become evident that traditional methods and conventional wisdom often do not in fact achieve these goals. Operating policies at many mines ensure that shareholder value is not maximized. Changing the overall strategy can provide significant value gains. Typically, the new optimal plan involves a significant increase in the cutoff grade, at least in the earlier years. An increase in the underground development rate or open cut stripping rate is often associated with this, at least in the short term, to establish the new strategy. Cost minimization is found to be counter-productive. Counter-intuitive plans are often found to be optimal. For example, optimal cutoffs for different parts of an underground mine may be significantly different, even if mineralisation and cost structures are similar. Sub-optimal strategies are also frequently found to have a significantly greater financial risk than optimal plans, which have been found in many cases to be relatively insensitive to changes in major value drivers, such as metal prices. This paper shows how identifying and then operating within the framework of an optimal strategic plan can have substantial benefits over being continually driven by short-term tactical issues.

Jan 1, 2009

By P. Jordan

The practice of ilmenite smelting in electric arc furnaces has been researched and published over the last few decades. An issue that has not been addressed is the understanding of the properties of ilmenite smelting reductants, and linking these properties to the subsequent smelting behaviour in the furnace. The reduction mechanism of ilmenite smelting is not fully understood, but it is believed that the Boudouard reaction plays a role. This paper investigates the behaviour of a number of reductants when reacted with CO2 at different temperatures. Keywords Boudouard reaction, carbon reactivity, reductants, ilmenite smelting.

Jan 1, 2011

By G. Lyman

The cross-belt sampler is a device that is very widely used even though it has not been ratified by the Standards associations. This paper is concerned with the bias testing of two cross-belt sampler designs against stopped belt samples and a cross-stream cutter at the belt end. The bias analysis is carried out using size distribution as the analyte and conventional t-testing and the Hotelling T squared test, which are compared for their effectiveness. The paper considers the issue of detectable bias and the statistical planning of bias tests.

Jan 1, 2009

By N. C. Joughin

A simplified economic model is derived for the financial return from a new gold mining project. The model is used to analyze the effects of changes in the mining rate, capital costs, working costs, value of the reef and the stoping width. The most effective avenues for improving the return from a new project are indicated. It is shown that those technological innovations which would improve the return significantly, and therefore make it possible to open more mines, are the use of smaller mines, means for improving the mining rate to capital costs ratio for smaller mines, planning and control of mines by computer simulation, an improved mine valuation procedure and means for mining at a decreased stope tramming width.

Jan 1, 2014

By M. H. Tyeb, C. Banerjee, A. K. Majumder

The primary requirement from a hydrocyclone is the classification of the feed solid particles. Particle classification occurs inside a hydrocyclone by virtue of the relative radial distribution of the suspended particles, based on their size and specific gravity. The particle classification behaviour in a hydrocyclone is experimentally studied in this paper. The phenomenological features of the air core at different feed solid concentrations and the distribution of the solid concentrations in the hydrocyclone are also analysed by the theoretical study of flow features in a steady Rankine vortex. Semi-empirical models for predicting the hydrocyclone performance in terms of flow split ratio, and cut size have been developed using the background knowledge of convoluted hydrodynamics. In addition, to validate the classification performance of a smaller diameter hydrocyclone, the potential of the present model is extended for envisaging the same for larger diameter hydrocyclones. A comparison between the model predicted values and the measurement data shows a good match. Keywords: Hydrocyclone, classification, Rankine-vortex, air core, modelling

Jan 1, 2020

By C. Rodrigues

This investigation compares the gas adsorption behaviour and capacity of three bituminous coals from South Africa, of similar rank, by assessing the characteristics of the raw coal, as well as the resulting float and sink fractions (at 1.80 cm3/g) obtained by density separation of crushed coal samples. Calculations were also made to obtain the raw coal gas storage capacity from the weighted contribution of both float and sink fractions results, thereby permitting comparison with the analysed results of the raw coal. The study demonstrated that the clean fraction of a coal has the highest capacity to retain gas in the sorbed state, followed by raw coal, and lastly the sink fraction, and re?confirmed previous investigations that showed minerals to be inhibitors of gas adsorption and retention.

Jan 1, 2008