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It is well known that the ability to influence project value reduces significantly as planning progresses and decisions regarding project parameters are made. However, at the prefeasibility stage in particular, where one of the main aims should be to evaluate a wide range of options in order to select the best for more detailed further study, there is often a reluctance to spend the time and money needed to do this rigorously. This paper demonstrates, by a number of case study examples, how significant increases in value may be obtained by fully evaluating the combinations of alternatives for various project design parameters, including (though not limited to) mining methods, haulage methods, mining rates, processing methods and rates, sequencing of mining, and cut-off grades, with changes and upgrades over time where applicable. The additional value unlocked is typically orders of magnitude greater than the additional cost of the more comprehensive study. The dangers of misuse of simplistic sensitivity analyses and failure to identify how strategies might change in response to changes in external factors are also illustrated, and the importance of selecting the best `grade descriptor' is discussed.

Jan 1, 2007

By T. M. Russell

"Face mapping is a simple but invaluable means of geological and geotechnical data acquisition whereby intact rock properties, rock mass properties, discontinuity properties, and structural orientation can be assessed. Although traditionally done via direct contact with the mapping face through techniques such as line mapping or window mapping, remote face mapping using various digital techniques has become increasingly popular in recent years. Sishen is a large open pit mining operation requiring a comprehensive geotechnical data-set to evaluate pit wall design and stability with the necessary level of confidence. Geotechnical borehole data, face mapping data, geotechnical laboratory testing data, and implicit structural models provide the main sources of this information. Although a large geotechnical borehole database has always been maintained at the mine, face mapping has in the past been restricted to sporadic and isolated stability assessments. In 2013 the mine acquired a terrestrial laser scanner with the resolution, photographic capabilities, and software required to carry out geotechnical face mapping. A face mapping procedure was set up based on accepted face mapping methods, the data requirements of the mine, and capabilities of the laser scanner system. Mapping data obtained from the scans was integrated into the Acquire geological data management system, a purpose-designed structured query language (SQL) database system used for storing the mine’s geotechnical data. Within the geotechnical design process, having face mapping data available has improved confidence in the properties of the rock mass and structural environment, allowing for better definition of geotechnical design sectors. Overall, the face mapping and geotechnical analysis features of the terrestrial laser scanner in use make it an invaluable geotechnical data capture tool, provided a system is in place to store mapping data in a manner that allows for meaningful rock mass and structural information to be produced. IntroductionFundamental to the geotechnical design process is the acquisition of a reliable and complete geotechnical data-set. Geotechnical data acquisition will typically commence during the early stages of a project and continue well into the operational life of the mine, with the data confidence progressively increasing as the amount of data captured increases. Sishen mine currently bases all open pit geotechnical designs and geotechnical risk assessment on geotechnical borehole data in conjunction with interpreted structural models. Boreholes are logged and the data is captured in an ongoing process. This process forms the initial step in the geotechnical design and risk assessment process whereby the raw data is used to classify the strength properties for each lithology, provide inputs for geotechnical block models, and ultimately provide the inputs for slope design analyses. To date, borehole data has provided the only largescale, organized data-set for input into geotechnical analyses at Sishen. Although borehole data is the best and most comprehensive form of geotechnical data, there are some shortfalls that can be addressed by other data collection methods. These shortfalls are as follows."

Jan 1, 2018

By M. H. Moys, J. Engelbrecht, N. Terblanche

Interface levels in flotation columns are generally measured with the aid of a pressure-sensitive Instrument, e.g. a differential-pressure cell. This paper criticizes the use of this type of measurement, and discusses other methods that are claimed to give more accurate measures of interface levels. The paper focuses on the development of methods based on the measurement of conductivity across the froth-slurry interface. These are often sabotaged by variations in the conductivity of the feed slurry, particularly when the pH of the slurry IS being controlled, e.g. In sulphide flotation. Methods of improving the accuracy and reliability of this technique are described. The result IS a robust, easy-to maintain level-control scheme that successfully rejects large disturbances in plant operation (including a 5:1 change in slurry conductivity) while controlling levels to an accuracy of I 4 cm.

Jan 1, 1992

By D. Yu Pleev, V. G. Krivolapov

Mines of Southern Kuzbass working out, basically, coal formations of flat seams. Seams, as a rule, are inclined to self-ignition. Detection at early stages of the centers of endogenous underground fires has great value for safe conducting mountain works. One of methods of detection of an early stage of underground fires in the worked out space is the method of superficial radon survey. In the report the method is de-scribed and examples of superficial radon survey on concrete layers are given.

Jan 1, 2003

By F. D. Agrensa, J. Hadjigeorgiou, E. Storimans, S. J. Thorpe

Reinforcement and surface support are part of an integrated system that transfers and shares loaduntil the excavation surface is stabilized or until the ground support system fails. Steel mesh is the most popular primary surface support element in underground hard rock mines in Canada. Mesh straps are a secondary surface support that provide additional containment as they distribute the load between and across the reinforcement elements. This investigation addresses the role of steel properties, and in particular steel chemistry, in the long-term performance of mesh and mesh straps when exposed to an aggressive corrosive environment. It reports on comparative accelerated corrosion studies to compare the resistance to corrosion of different surface support elements. This has significant implications on the choice of surface support and the anticipated rehabilitation requirements.

Oct 9, 2024

By F. J. N. Stassen

SYNOPSIS The effect of conditioning energy on the flotation of gold, U308, and pyrite was investigated in the range 0,1 to 100 kWh per tonne of dry ore for various combinations of conditioning time and impeller speed in a cylindrical con¬ditioning tank. It was found that, when the conditioning energy was increased to between 5 and 10 kWh per tonne of dry ore, the total recovery and flotation rate of the valuable minerals (expressed as Klimpel parameters) increas¬ed substantially. The Klimpel parameters are dependent on conditioning energy, but are independent of condition¬ing time or impeller speed (at constant conditioning energy). The Klimpel parameters of the gangue are indepen¬dent of conditioning energy.

Jan 1, 1991

By C. P. S. Barnard, D. G. Krige

Objective justification on economic grounds for expenditure aimed at improving the quality of the underground working environment requires a suitable measure of any improvement in productivity that would result under routine working conditions. For this purpose, a composite production criterion is suggested, as well as its correlation under actual operating conditions with various factors directly affecting productivity and the environment. Of the environmental factors, wet-bulb temperature appears to be the major factor affecting productivity. The production data given indicate that a decrease in the wet-bulb temperature of 1OC can be expected to result, on average, in some 3 to 4 per cent increase in productivity; in the higher temperature ranges, this percentage could be much higher.

Jan 1, 1981

By Mike Rogers

Platinum production in Southern Africa amounted to 80% of world production in 2005with a small increase from 5 117 000 ounces to 5 275 000 ounces. For the seventh consecutive year the platinum market is on course to record a moderate deficit in supply. This is reflected in the price increase from a trading range US$860 to US$880 in June 2005 to an excess of US$1 200 in September 2006. Southern Africa, with its extensive platinum reserves, will continue to be the dominant platinum producer and has a number of new mines in an advanced stage of planning. The slogan ?Platinum Surges Ahead? was selected to describe the exciting and vibrantnature of all aspects of platinum mining, beneficiation and marketing. This conference will cover these aspects from exploration and orebody delineation, through mine design, development and operation to mine closure; mineral beneficiation, marketing and compliance with the Mining Charter will also be subjects for discussion and debate. It is also anticipated that the issue of overall increases in productivity, through the introduction of technology, will demonstrate Southern Africa?s status as a premier mining district. It is my pleasure to welcome delegates from abroad and locally, on behalf of the SAIMM, to the Second International Platinum Conference ?Platinum Surges Ahead?. I trust that you will find the proceedings informative and value adding and will participate in the discussions and debate in order to obtain maximum benefit from the conference. I am sure that the post-conference tours will be interesting and of great benefit to participants. Finally, a big word of thanks to the members of the Organising Committee, the management and staff of the SAIMM, and to our willing sponsors, without all of whom this conference would not have been possible.

Jan 1, 2006

By M. A. El-Sayed

"Double oxide films (bifilms) are significant defects in light alloy castings that occur when, during melt handling, the oxidized surface of the melt is folded over onto itself and then entrained into the liquid metal, encapsulating a portion of the local atmosphere. These defects create crevices in the final castings and have been shown to decrease tensile and fatigue properties, and also to increase their scatter, making casting properties unreproducible and unreliable. This paper reports on two different experiments performed to study the behaviour of such defects in Al alloys. In the first experiment and as a proxy for a bifilm, air bubbles were held in an Al-5Mg alloy melt for varying periods of time before the melt was allowed to solidify. The composition of the gas content of the bubbles was subsequently analysed using mass spectrometry to ascertain how it changed with time. In the other experiment the influence of the age of bifilms on the mechanical properties of Al-5Mg castings was assessed by holding castings in the liquid state for different times before solidification, followed by mechanical property testing and SEM and EDX studies of the fracture surfaces of tensile test bars. This research could provide a better understanding of the behaviour of double oxide film defects, and may lead to the development of new techniques by which these defects could be eliminated, or at least deactivated, in light alloy castings. Introduction One of the major structural defects affecting the reproducibility of mechanical properties of aluminium castings is the double oxide film defect (El-Sayed and Essa, 2017; El-Sayed and Ghazy, 2017). This type of defect is usually created as a result of poor filling system design. Owing to the very high reactivity of liquid Al-Mg alloy with oxygen in the air, the surface of the liquid metal can be considered to be permanently coated with an oxide film (Weigel and Fromm, 1990). As a consequence of surface turbulence, the oxidized metal surface can become folded over onto itself, but not fused, and then submerged into the bulk liquid, with a portion of the mould atmosphere being entrapped within it (Campbell, 2003; Al- Sayed, 2016; El-Sayed, Hassanin, and Essa, 2016)."

Nov 1, 2018

By D. Moses, J. A. Onyango

Carbonatites are generally competent rock masses with rock mass rating class II rating 60–74. In spite of their competency, they tend to be affected by weak features like manganese-iron veins and/or in situ rock damage due to brecciation associated with carbonatite complexes. Rock slope failure in such hard rocks is complex since such structures within the rock mass form weak links that could potentially control slope instability. In this contribution, a numerical simulation using phase2 v 7.0 was carried out to investigate the influence of in situ rock damage on the stability of mine pit walls. The outcome reveals that, the existence of breccia in the competent rock mass has the capability to reduce the slope stability performance particularly at gentle dipping angles of emplacement in close range to the slope toe. However, as the emplacement position of breccia moves away from the pit wall, the stability performance increases at gentle dipping angle <50º. On the contrary, at the dipping angle of 50° the performance of slope reduced, and at steeper angles >50° the impact becomes negligible. Thus, from a series of analyses, mine design in brecciated rock masses, the ratio of 1:5 between the breccia distance from slope toe and pit depth should be implemented to counter its impact, and if the breccia is within or close to the pit limit, a deliberate effort must be made to mine it out.

Sep 1, 2025

By B. Oladipo, E. Govender-Opitz, T. V. Ojumu

Bioleaching, one of the several important processes of biohydrometallurgy is an accepted technique for the extraction of desired metals from sulphide ores. Although the mechanism is well understood, the slow metal extraction rate due to passivating layer and ferric ion precipitation, especially in a typical chalcopyrite leaching, impact negatively on the overall efficiency of the process. Iron precipitates are common in many biohydrometallurgical operations and these precipitates represent the exit route for undesired iron, alkali ions or sulphate ion from the processing circuit. While there have been reports on approaches to slow the formation of these precipitates by manipulation of various operating conditions such as pH, redox potential and temperature, the precipitates become highly significant over the long term in the continuous operation of bioleaching and may render heap impermeable. Although there is evidence supporting the nature of the passivation to be precipitates of iron, their scavenging mode of reducing extraction efficiency is still not well understood. This paper thus discusses iron precipitation in biohydrometallurgical processes, including its formation and significance on bioleach processes. The paper also details the associated passivating species identified with heap bioleaching of sulphide minerals and provides some insight into sorption mechanism that limits metal recovery in a typical bioleach operation. Keywords: Iron precipitation, bioleaching, chalcopyrite, passivation, jarosite, metal sorption

Jan 1, 2020

By L. H. Lindstad

The paper reviews the tapping process and the major wear mechanisms on the tap-hole, including wear from tapping tools. Measured temperatures in different tap-holes are related to choice of binder and material for repair pastes. The strength and disadvantage of carbon and silicon carbide materials are compared. Normal daily and weekly maintenance of tapholes is described, together with the major repairs that are done during longer furnace shutdowns. The objective is to show that the type of repair and repair material needs to be adapted to each individual furnace.

Jan 1, 2014

By P. Gonzalez

Minera La Parreña, S.A. de C.V., Milpillas operation is an underground mine designed to process 8 352 tons of ore per day for the recovery of copper through crushing, heap leaching, solvent extraction and electrowinning facilities. In order to optimize copper recovery during leaching, the ore is crushed to 13 mm and subjected to primary sampling every 15 minutes for metallurgical accounting. At the same particle size, primary sample goes to secondary sampling and then, the secondary sample is crushed to 2 mm before tertiary sampling. The tertiary sample is sent to laboratory where a final sample is obtained and pulverized to 106 microns for copper assay. This paper shows a review of sampling strategy focused on minimizing or eliminating sampling errors and an experiment designed to determine copper head grade profile as well as the best sampling frequency.

Jan 1, 2009

By X. Ndlovu

Underground observations in a coal mine have indicated failure oft he immediate roof above the bords. Careful observations and photographic recording of occurrences of these roof failures, termed ?roof guttering?, have been made. The occurrence of guttering results directly in roof instability, and indirectly, due to the interaction of the guttering with natural planes of weaknesses in the immediate roof rock. In this paper, relevant observations of roof guttering, possible mechanisms of formation of roof gutters, laboratory testing for determination of material strength and deformation properties, and numerical analyses to explain underground observations are described. Mapping of roof failures showed that these took place mainly towards the centre of the roadways. Roof guttering was observed often to occur violently and with little warning. Occurrence of roof guttering has a negative impact on production?some panels are abandoned, production times are increased and safety of workers is compromised. The numerical stress analyses showed that, although none of the constitutive behaviour criteria used predicted the observed underground failures correctly, the extension strain criterion gave the best agreement.

Jan 1, 2007

By J. A. Theron

"This paper provides guidelines on performing mass and energy balance modelling involving coal and coal derivatives. Usually, the inputs to a pyrometallurgical process would be specified in terms of elements and compounds. Reliable thermochemical data is more widely available for species involving uniquely defined, relatively smaller molecules. However, in the case of coal, the molecules are extremely large and not uniquely defined. Consequently, modelling processes involving coal and its derivatives have several potential pitfalls. These are outlined in the present paper. The main findings are as follows:•,Coal proximate analysis should not be regarded as absolute; it could vary with several parameters, including heating rate •,For modelling, the use of ultimate analyses should be considered a preferable option to proximate analyses, where, ‘fixed carbon’ and ‘volatiles’ are not defined in terms of chemical composition •,Significant errors could be made if the larger molecules are neglected during calculation of the calorific value (CV) of coal gas (the gas liberated when coal is heated in the absence of oxygen) •,For elemental analyses, the oxygen content (which is calculated by balance) should be checked to ensure it is within the expected range •,For representation of sulphur in coal, double-counting due to SO3 in the ash analysis should be avoided •,Potentially, oxygen in coal could be represented as O2, H2O, CO, or CO2; however, use of some of these species without considering the experimentally determined gross CV results in significant errors in the energy balance. If coal enthalpy is calculated from elemental analyses without correction, representation of coal oxygen as H2O(l) gives reasonable accuracy (up to 6.9% error for a set of South African coals). Coal volatiles could be represented by a complex mixture of compounds, even using different oxygen-containing species than the abovementioned four, provided the enthalpy is corrected •,It is recommended that an ‘enthalpy correction value’ is incorporated in energy balances involving combustion, devolatilization, or conversion of coal and coal derivatives, e.g. coke, char, or tar. That would imply that proximate analysis, elemental analysis, as well as the gross CV would be required for all solid or liquid coal-derived substances being modelled. No other correction due to the form of carbon being different than graphite should be used, as that would imply doublecounting some effects."

Jan 1, 2014

A powerful, interactive metallurgical process simulator for use on micro- computers has been developed in the Department of Metallurgy and Materials Engineering at the University of the Witwatersrand. MICROSIM presently allows simulation of all ore-dressing flowsheets and a selection of hydrometallurgical unit operations, and is extendable to all such processes. MICROSIM is written in Pascal. This modern language provides very versatile data structures which can be effectively used to solve the major problem in generalised simulation programs, namely storage and transmission of data relating to liquid and solid phases. Dynamic memory allocation allows optimal utilisation of computer storage space. The simulator utilises very efficient precalculation algorithms that determine the tear streams for optimal sequential modulator calculation convergence. Microcomputer graphics simplifies flowsheet specification, and form-filling data capture with supplied default values eliminate most common input errors.

Jan 1, 1987

By E. L. J. Kleynhans, J. I. J. Fick, J. P. Beukes, P. G. van Zyl

"Ferrochrome (FeCr) is vital for the production of stainless and high-alloy ferritic steels, since it is the only source of new Cr units. FeCr production is an energy-intensive process. The pelletized chromite prereduction process is most likely the FeCr production process with the lowest specific electricity consumption (SEC), i.e. MWh/t, currently in operation. However, due to increases in costs, efficiency, and environmental pressures, FeCr producers are attempting to lower their overall energy consumption even further. Recently, it was proven that pre-oxidation of chromite ore prior to pelletization and prereduction significantly decreases both the SEC and lumpy carbonaceous reductants required for smelting. This paper presents the first attempt at conceptualizing the technoeconomic feasibility of integrating chromite pre-oxidation into the prereduction process. Financial modelling yielded a net present value (NPV) at a 10% discount rate of approximately R900 million and an internal rate of return (IRR) of approximatelyy 30.5% after tax, suggesting that the implementation of pre-oxidation prior to pellet prereduction may be financially viable. Sensitivity analysis indicated that the parameter with the greatest influence on project NPV and IRR is the level of prereduction. This indicates that the relationship between maintaining the optimum pre-oxidation temperature and the degree of prereduction is critical for maximium process efficiency. IntroductionStainless steel is a crucial alloy in modern society. Virgin chromium (Cr) units used in the manufacturing of stainless steel are obtained from ferrochrome (FeCr) – a relatively crude alloy consisting predominantly of Cr and iron (Fe) (Murthy, Tripathy, and Kumar, 2011; Beukes, van Zyl, and Ras, 2012). FeCr is produced mainly by the carbothermic reduction of chromite ore in submerged arc furnaces (SAFs) and direct current arc furnaces (DCFs) (Neizel et al., 2013; Beukes, Dawson, and van Zyl, 2010; Dwarapudi et al., 2013). The energy required to heat, smelt, and reduce the chromite ore to the metallized state is supplied by electricity (Pan, 2013). FeCr production is an energy-intensive process, with a specific electricity consumption (SEC) varying from 2.4 MWh/t to more than 4.0 MWh/t FeCr produced, depending on the process applied (Pan, 2013; Neizel et al., 2013). Daavittila, Honkaniemi, and Jokinen (2004) stated that the typical operational costs of FeCr smelters can be divided into four categories, i.e. chromite ore (30%), carbonaceous reductant (20%), electricity (30%), and other production costs (20%). This makes electricity consumption the joint largest factor that influences operational costs in FeCr production."

Jan 1, 2017

Sampling In The Coal Industry Exploration, Mine, Met and Environmental Sampling EMMES 2005 3, 4 November 2005

Jan 1, 2005

By B. X. Huang

Hydraulic fracturing technology is presented as a solution to improve permeability and thus solve the extraction problem of coal seam gas in low-permeability gas-bearing coal seams. Given an existing group of original cracks, the propagation of main hydraulic cracks and hydraulic wing cracks was simulated using realistic failure process analysis software. The process represents the structural transformation of hydraulic fracturing and permeability improvements caused by it. In addition, a field test for improving the permeability of gassy coal seams by hydraulic fracturing was also conducted. The propagation of the main cracks and wing cracks by hydraulic fracturing forms a network of original joint cracks, hydraulic wing cracks, and main hydraulic cracks, which improve the permeability of the coal seam. High-pressure water in the drill hole and in the main hydraulic cracks permeates the two flanks of the hole, forming the permeating water pressure. With an increase in drill water pressure and an extension of the main hydraulic cracks, the permeating water pressure on both sides of the main hydraulic cracks in the coal mass also increases. Hydraulic cracks tend to form connections through rock bridges. The extension of hydraulic wing cracks through connections in the rock bridges between the cracks transforms the rock mass to a fractured structure and improves its permeability. Hydraulic fracturing technology for improving permeability in underground conditions can increase the amount of gas drainage by a factor of 15. A stress relief area develops at a radial distance of 10-2.0 m from the hydraulic fracturing drill hole, while an area of rising stresses, called the pressurized area, develops a further 15 m away from the pressurized hole. Practice has proved the existence of the stress transfer phenomenon and the high stress area after fracturing. This kind of hydraulic fracturing technology is more effective in holes drilled from underground than in surface drill holes, with respect to costs and controllability, and is therefore the major trend in gas drainage development in coal mines.

Jan 1, 2012

By Matthew D. Viergutz

MECS? HRS technology has reliably recovered intermediate pressure steam from sulphuric acid plants for more than 20 years. This steam can either generate electricity or replace steam produced by an existing fuel-fired boiler. As worldwide greenhouse gas emissions continue to rise, industries are looking for novel and cost effective solutions to reduce pollution, particularly carbon dioxide, from their plants. Waste heat recovery technologies such as HRS offer new and existing plants the opportunity to maximize energy efficiency while reducing their reliance on energy supply from external sources. This paper offers a unique look at energy recovery in sulphuric acid plants and how recent innovations in MECS? Heat Recovery System technology make HRS more financially viable ? and more green - than ever.

Jan 1, 2009