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A localized nonlinear recoverable resource estimate technique has been applied using typical feasibility or new mining drilling data configurations drawn from a massive database from a mined-out area on a hydrothermal gold deposit. The results were then compared with the corresponding 8 m x 5 m grid grade-control data in order to determine the efficiency of the approach and the validity of the recoverable resource estimates for mine planning and financial forecasts.

Jan 1, 2014

By L. W. Burger

The need to establish and harmonise methodologies to quantify air emissions, atmospheric dispersion and the consequences of air pollutants (especially hexavalent chromium) from the ferrochrome industry became important aspects with the increasing demands for comprehensive impact assessments. The paper includes a synthesis of current knowledge on the following aspects: ? Locally and internationally accepted methodologies for the quantification of chromium emissions, including sampling methods and emission factors; ? A compilation of recognised and accepted air quality sampling and laboratory analysing techniques; and, ? Dispersion modelling and impact assessment tools. Depositing and removing materials from the chromium ore stockpile and wind erosion of exposed stockpiles result in mainly chromite emissions unlikely to contain significant amounts of hexavalent chromium. Pre-treatment processes such as drying, crushing and screening also produces chromium emissions, but mainly as trivalent chromium. The smelting of chromium is the major source of chromium emissions - open furnaces have the highest uncontrolled chromium emissions, followed by semi-closed and closed furnaces, respectively. Based on the current knowledge on emission rates, interim emission factors for particulate, total chromium and hexavalent chromium releases are provided. Ambient sampling and analytical methods to determine environmental exposure of the general public require that hexavalent chromium needs to be quantified in very low concentrations. Suggested sampling and analytical methods for both source characterisation and ambient monitoring are provided. The selection between dispersion models needs to be based on the size of the modelling domain and the complexity of the terrain. The discussion on dispersion models includes the US EPA?s Industrial Source Complex Model (Version 3), the AERMET/AERMOD suite of models and the CALMET/CALPUFF suite of models. Guidelines are also proposed for environmental exposure assessments including cancer and non-cancer health effects.

Jan 1, 2004

By E. Laine

Rock density determinations are necessary for ore resource evaluations from estimated block grades in g/t. Rock density depends on the mineral composition and, thus, it is specific for each rock type. The rock density distributions for different rock types are often symmetric. Hence, the arithmetic mean is a good approximation for the average density for lithological units. However, there may exist spatial variation in density values due to alteration, fracturing and original heterogeneities such as layering. This study compares the kriged density model with the one with constant density values for different lithological units in the evaluation of metal amounts in rock blocks. The case study consisted of rock densities measured from the drill cores at Ahmavaara PGE deposit in northern Finland. The used Ni contents were simulated in accordance with the spatial distribution of rock densities. The Ni amounts in 2x2x2 m3blocks are higher for the kriged densities than for the average densities. The difference is increasing with the increasing metal amounts due to the nonlinear correlation between Ni content and rock density. The final effect on the resource estimation depends on the cutt off grade and prices of the metal, for example, for a very valuable metal the small differences are significant

Jan 1, 2003

By R. G. Votteler, A. C. Brent

"The business performance of mining corporations in South Africa is adversely affected by the constantly increasing electricity costs. The most commonly used power sources are the national utility supplier via a grid connection, and on-site diesel generators. Previous research has identified the renewable sources of solar photovoltaic (PV), onshore wind, and geothermal energy in hybrid versions with current sources as possible opportunities to counteract rising electricity costs. To provide a clear understanding of the new, developing market of renewable energy sources, this research is divided into two papers. This first paper investigates the internal business structure of mining corporations in order to evaluate electricity generating sources. The multi-criteria decision analysis (MCDA) method is selected as the most suitable approach for this. The paper identifies the criteria used by mining corporations to evaluate possible electricity generation sources for self-generation by means of the corporations’ own investment. Four mining corporations with several mining locations were interviewed. The interviews revealed both new and identical evaluation criteria when the findings were compared to earlier MCDA adaptations analysed in the literature review. The second paper (Part 2) combines current knowledge about the external macroeconomic environment with the findings about the internal environment described here. MCDA is adapted in Part 2 and implemented to analyse and compare current to hybrid renewable sources from the perspective of mines. IntroductionMining corporations in South Africa are currently adversely affected by increasing electricity prices. Electricity is supplied mainly by Eskom1 and, especially in remote locations, by on-site diesel generators (Boyse et al., 2014). Electricity price increases, emanating from diesel price hikes and Eskom, have escalated the total operational expenditure on electricity by the largest mining corporations from 8% to 20% of total operating costs in the past seven years (EIUG, 2015). The reliability of electricity supplied by Eskom has decreased drastically (Govender, 2008), and the prices will increase annually by at least 13% until 2018 (Numbi et al., 2014; Eskom, 2015b). In addition, the South African government plans to introduce a carbon tax on greenhouse gas emissions (Alton et al., 2014)."

Jan 1, 2017

By B. P. Watson

The Bushveld platinum group metal deposits are two distinct, shallow-dipping stratiform tabular orebodies and strike for many hundreds of kilometres. Mining is extensive, with depths ranging from close-to-surface to 2 000 m. The mining method is a variation of planar open stoping. Pillars are widely used to support the openstopes. Little work has been done in the past to determine pillar strength and pillars have been designed using experience and formulae developed for other hard-rock mines. This has led to oversize pillars with consequential loss of ore or undersize pillars resulting in potential collapses or pillar bursts. This paper describes a back-analysis of pillar failures at Impala Platinum, just north of Rustenburg, and provides insights into pillar behaviour. Strength formulae are presented for Merensky Reef pillars at Impala. These formulae may be used cautiously on other platinum mines with similar geotechnical and geomechanical conditions.

Jan 1, 2008

By I. W. van der Merwe

Recently, a new kind of filtration has emerged, namely nano-filtration (NF). It is a membrane-based process which exhibits totally unique separation characteristics for dissolved salts as well as for many non-charged species. By exploiting the particular separation characteristics of this new membrane type, many unique and novel separations have been made possible. The basis for separation by nanofiltration is the negative surface charge of the membrane. This results in rejection of multivalent anions, whilst associated cations are also rejected to maintain electro-neutrality. This peculiar property enables separation of dissolved ions such as sulphate and copper from acid, whilst the acid may be purified for reuse. This paper aims at providing an overview of the principles of nanofiltration, illustrated by particular examples.

Jan 1, 1998

By D. F. Malan, Y. Jooste

"SynopsisScattered mining was practised on Kusasalethu Mine (previously Elandsrand Gold Mine) prior to 1998, but at deeper mining levels it was no longer feasible, since it would have resulted in unacceptably high stress levels and energy release rates. Longwall mining was not adopted at these depths as the mine required a more flexible mining method owing to the highly variable grade and the presence of geological structures. A mining method was developed that consisted of dip stabilizing pillars for regional support, as well as bracket pillars to clamp geological structures. A strict sequence of extraction was followed and this, together with the particular layout, was called the ‘sequential grid mining method’. This method addressed two key problems, namely negotiating adverse geology and the erratic grade of the Ventersdorp Contact Reef (VCR) orebody. However, a significant drop in production rates resulted in the need for alternatives and improvements to the original mine design. Modifications to the design were proposed in order to increase production rates, and an investigation to consider the rock engineering implications of these modifications was conducted. The study indicated that the modified method, called the ‘multi-raise mining method’, appears to be feasible and might address some of the production problems that were experienced with the original sequential grid design. An analysis of actual seismic data showed no significant differences between the original sequential grid mining and the implemented multi-raise mining. The numerical modelling of the mining layouts showed slightly higher interim energy release rates (ERRs) and average pillar stress (APS) levels during the extraction process. The final values are nevertheless identical to that of the original sequence. The study also investigated the use of a modelled moment method to analyse future seismic trends. The study illustrated that the expected seismic trends will be very similar for the multi-raise method compared to the original sequential grid mining method. This study is nevertheless considered of a preliminary nature and ongoing monitoring and analysis of seismic data at the mine is required to verify the response of the rock mass to the modified sequence and increased extraction rate. In particular, future work needs to investigate the effect of mining rate (advance rates in individual panels as well as volume of mining in particular raise lines) on the level of seismicity."

Jan 1, 2015

By Reginald N. Boryor, Steven D. Woods

1.0 Introduction ?Low grade, high tonnage, open pit gold mine. ?Gold bearing Tarkwaian conglomerates. ?Reverse Circulation percussion drilling (25m X 25m grid). ?Composite 1m intervals, logged and split in the field to provide±2Kg samples. ?Samples used to build grade control block models using SURPAC. ?Approximately 100,000-130,000 meters drilled per year. ?RC samples are assayed using Rapid Cyanide Leach (RCL). ?Check assays are done using Fire Assay

Jan 1, 2005

By A. D. Storrie

An underground wet shotcrete trial was completed last year to determine the effectiveness of wet shotcrete as an alternative support mechanism to dry shotcrete in the kimberlite environment. The wet shotcrete was manufactured at the underground batch plants, transported to site using an agiecar and transferred to the shotcrete pump. The wet shotcrete is pumped to the nozzle where compressed air at 7 bar and an accelerator, Meyco SA 160, is added and enables the shotcrete to be placed successfully onto the tunnel wall. No tunnel guard was previously placed on the sidewall and hangingwall. Geotechnical testing indicates that the Grace fibre performed extremely well with the energy absorption tests at 7 kg/m3and 8kg/m3where both achieved over the mine requirement of 750joules. The Grace fibre and wet shotcrete mix also achieved a compressive strength in excess of 55 MPa, well above the 45 MPa requirement for Premier Mine. The recommended wet shotcrete mix design is therefore based upon: [Material/ CriteriaQuantity/m3Units ?Lafarge 42.5 Duratech500kg ?Condensed silica fume40kg ?Rayton Sand1.558Ton ?Delvocrete stabilizer 103.6litres ?Glenium 27CH5.4litres ?Meyco TCC 7355litres ?Water230litres ?Meyco SA16025litres ?Fibre8kg ?Cement/Water Ratio2.35? ?Water/Cement Ratio0.43? ?Flow615 mm] If the wet shotcrete system is implemented there is a potential for Premier Mine to make major savings. In South Africa there are two suitable wet shotcrete machines available for the mining industry, the Spreymec, manufactured by Tamrock and the Fermel/Meyco wet shotcrete machine. The Spreymec is a fully imported machine. The Fermel component is manufactured in South Africa and the Meyco shotcrete components are imported and supported by MBT (Master Builder Technologists) in South Africa. The Fermel/Meyco machine is assembled in South Africa. Premier Mine has allocated some R2, 100,000 towards the implementation of the wet shotcrete system. If implementation is successful there should be an internal rate of return gain of 76% with regard to this project.

Jan 1, 2001

By L. Arnberg, E. Ott

The microstructure of ferrosilicon is important since it controls the disintegration of the material during crushing and thus the generation of fines. Therefore a study of the microstructure formation during solidification of pure FeSi(75wt%Si) and FeSi(75wt%Si) containing 1.2wt%Al and 0.2wt%Ca has been initiated. The material has been cast into rods of 8mm diameter, which have been remolten by induction heating and directionally solidified in a Bridgman apparatus. This allows the temperature gradient and the growth rate to be controlled independently. The temperature history during solidification has been recorded by a thermocouple in the melt. Growth rates have been varied between 5 and 400µms-1 and temperature gradients between 3 and 14°Kmm-1. The microstructures show a large dependence on the solidification conditions. The crack formation in the alloys has been studied and found to be strongly related to the microstructure.

Jan 1, 2004

By J. Gummer, M. Williams, S. J. Hawksworth

A common problem encountered in British coal mines is bearing failure on conveyor system idler rollers, which on occasions has led to fires. The UK Mines Inspectorate initiated a study of such failures to assess the potential for ignition of explosive atmospheres. As part of this study HSL have developed a system to measure the temperatures generated within the bearings during controlled failure. Temperatures are measured using both infrared thermal imaging and contact thermometry. The work to date has shown that temperatures well in excess of the auto-ignition temperature of methane can occur.

Jan 1, 2003

By C. Sarkar

Increased competition in today’s global economy has put mineral industry under excessive pressure to effectively manage production assets to generate business wealth. Capital intensive industry (CII) organizations are seeking ways to manage skill resources, internal processes, and organizational networks with a view to reduce the cost of ownership of assets and increase efficiency of operations and service. The emerging concept of Enterprise Asset Management(EAM) is a collection of business processes that allow CII with right focus on return on investment on assets, to make right decisions on planning, acquisition, maintenance, operation, rehabilitation, and disposal of assets. Information technology (IT) can drive significant returns if the infrastructure covers seamlessly all business processes and all systems, like geographic information system, maintenance management, investment management, laboratory information management, and supervisory control and data acquisition system. The simple approach to IT in the past with disconnected silos of technology, information, and business processes cannot deliver the expected benefits under the modern business environment. Identification of business and application component is a prerequisite for the development of an asset management system that links effectively disciplined processes having characteristics of agility, speed, and integration. This paper discusses various issues and outlines the steps for developing an asset management roadmap in an organizsation. It also presents major business and application components of the system. Keywords: Enterprise asset management, Business architecture, Business component, Application component, Asset ownership, Asset operations, Information technology, Capital Intensive industry

Jan 1, 2003

By J. P. F. Charpin

The transport of large boulders in a furrow from a mining area to a nearby pond was considered. The furrow is filled with a mixture of water and soil particles flowing down to the pond at high velocity. Due to operating constraints, the slope of the furrow is reduced progressively. A relationship is derived, relating the slope of the furrow and the composition of the fluid to the maximum size and shape of the transported boulders. The characteristics of the boulders carried all the way down to the pond may then be determined.

Jan 1, 2007

The spatial distribution of copper grades at the Mansa Mina project is highly variable due to the presence of high grade copper/silver/arsenic breccia bodies. Copper grades within the breccia bodies tend to average about 4.5% copper while grades in the surrounding stockwork average about 1.0%. The breccia is known to occur in the vicinity of significant controlling structures, however, the outline and therefore the thickness of the bodies are far from regular. Due to the high grade of these bodies a significant proportion of the value of the project is derived from the breccia tonnages. The irregularity in the outlines/thickness translates into an uncertainty in the breccia tonnage and therefore in the value of the project. Acknowledging the economic importance of the breccia bodies and the risk associated with the breccia tonnage uncertainty, significant additional drilling has been proposed to both understand the spatial distribution of the breccias and reduce project risk. The costs associated with this additional drilling are not inconsequential; thus, a reasonable question is ‘what value is derived from this additional drilling’? To obtain an answer to this important question, a simulation approach is applied. First the deposit is simulated using the existing drilling and the uncertainty in the resource is defined. Next the proposed drilling program is simulated and the simulated data are added to the existing data. Using this expanded data set a second simulation of the deposit is created and once again the uncertainty in the resource is defined. Using this approach, the reduction in the uncertainty in the resource can be determined. To convert this reduction in uncertainty (or reduction in risk) in the stated resource into a dollar value, a method of defining the increase in the project rate of return necessary to account for risk is presented. Using the two different rates of return, the difference in project NPV and hence the value of additional drilling is determined.

Jan 1, 2003

By V Kveldsvik, N Ragvin, T Eiken, G Grøneng, G V. Ganerød

Catastrophic rock slope failures have caused destructive tsunamis in Norwegian fjords. At the Åknes rock slope the tsunami generating potential is large due to the potential large volume involved in a possible catastrophic failure. Widening of the upper crack has been recorded since 1986, and in recent years, a quite extensive investigation and monitorin campaign has been conducted. Data from some of these investigations are presented and analysed with respect to a preliminary evaluation of the stability of the slope.

Jan 1, 2006

By J. Kirsch

Keywords: Pyrometallurgy, pneumatic transport, pneumatic transport Dense-phase pneumatic injection has begun to replace more traditional furnace-feeding systems. The paper describes the technology as it is applied to processes where the back pressure at the point of injection is greater than 50 kPaG. It reviews earlier systems of injection and more recent developments that address concerns for instantaneous control in modern smelters. The new technologies fall into two groups, (1) modified pressure-difference control (sub-divided into simple and complex) and (2) mechanical-feeder-based control. Features of current injection systems include feed splitting in two forms, passive and active, and co-current injection.

Jan 1, 2006

Viscosity measurement was carried out over a narrow range of silica content around the fayalite composition. A wide range of temperature and oxygen potential was covered where the slag was completely liquid. In order to keep the slag composition and the Fe3+/Fe2+ratio constant, theCO2/CO ratio was kept constant as the temperature was varied. Increasing the Fe3+content has little effect on viscosity for slags with a silica mole fraction of 0.31. At higher silica contents, increasing the Fe3+content brings about a small decrease in the viscosity.

Jan 1, 2004

By B. R. Broekman, D. W. Penman

Discussion by P.J Lloydt Broekman and Penman describe (J.S. Afr. Inst. Min. Metal., vol. 91, Aug. 1991, p. 261) the addition of sodium cyanide and zinc sulphate to the flotation feed at Prieska. They note that for 'safety sake, lime was added to the rod mil to raise the pH to 9,5', and that 'personnel working in the vicinity of the rod mil were required to wear gas masks'. Author reply to P.J. Lloyd We thank Dr Lloyd for his interesting contribution. As he correctly points out, the Prieska float had run with cyanide solutions at pH values of 6,4. In fact, it ran safely for extended period with the pH slightly below 6.

Jan 1, 1991

By Y. Chen, D. He, J. H. Potgieter

The demand for rare earth elements (REE) is increasing rapidly owing to the emergence of new cleanenergy and defense-related technologies. China’s dominates the world production of REE. In this paper, we review the ore characteristics of four typical REE deposits in China and discuss the conventional beneficiation techniques, including gravity and magnetic separation, flotation, and hydrometallurgical processing of these ores. Some of the latest laboratory findings and industrial applications, as well as the development of novel reagents for REE processing in China are presented. The REE beneficiation technologies developed and employed in China could constitute a good case study for many other emerging projects being explored around the world.

Mar 2, 2022

The roasting of sulphide ores and concentrates is often the first step in the production of metals or chemicals. In many processes, the production of sulphuric acid is viewed as a by-product, whereas in some plants production is an important economic factor. Regardless of the purpose, a pyrite roasting plant consists of mainly three plant sections: roasting, gas cleaning and sulphuric acid. With the addition of air, the pyrite concentrates are transformed into solid oxides and gaseous sulphur dioxide at temperatures of 600?1000°C. After cleaning and cooling, the sulphur dioxide in the roasting gas is further processed to sulphuric acid. Two types of reactors are used depending on the application: stationary or circulating fluid bed. For over 60 years, Outotec has progressively been developing the principle of fluidized bed technology in several different reactor types for a multitude of process applications. The versatility of the fluidized bed reactor system has manifested itself in the treatment of minerals, including solid fuels, and for metallurgical processes both in the ferrous and non-ferrous fields. Process applications have included roasting, calcining, combustion and charring of coals, as well as off-gas treatment. This paper provides a summary of the pyrite roasting technology currently used along with a simple cost comparison of pyrite roasting and sulphur burning processes.

Jan 1, 2009