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By A. E. Landsberg, K. C. Corin, G. Stroebel, J. A. Miller, M. Becker, H. J. J. Gordon

Geometallurgy represents an integrated approach to mine planning and operation whereby the naturally occurring ore variability and its effects on all key downstream activities in the mine life cycle are considered. Process mineralogy is one of the key components of this integrated approach. This paper focuses on understanding some of the mineralogical variability across the Swartberg Cu-Pb-Zn sulfide ore in South Africa and its consequent effects on flotation performance. This process mineralogy project is motivated by the planned changeover and expansion of the Black Mountain Mines concentrator to process solely Swartberg ore compared to the run-of-mine blend currently being treated at the plant. Eight samples spanning the main lithological units of the ore body are described using quantitative mineral-textural data and bulk sulfide batch flotation performance to establish five process mineralogical or geometallurgical units comprising: quartz-pyroxmangite-magnetite, quartz-amphibolemagnetite, quartz-magnetite, garnet-magnetite-quartzite and mica-quartzite ores. Important mineralogical characteristics affecting Cu, Pb and Zn recovery, grade and selectivity specific to the different ore samples are discussed. Ultimately, the use of ore-specific process mineralogical and geometallurgical knowledge allows for better mine planning and plant optimisation. Keywords: Flotation, polymetallic base metal sulfide ore, process mineralogy, ore variability

Jan 1, 2020

By Lutz Markworth, Wolfram Jaspers, Johannes Kottmann

PNEUFLOT® technology has been applied for the past 20 years in coal, ore and other minerals processing plants. During the last two years this technology has achieved a breakthrough with some 42 units being sold signifying a rising trend. »Humboldt Wedag Coal & Minerals Technology« has performed extensive research and development work over the last five years. The results of which were used to design a new fourth generation aerator. Humboldt Wedag, through its association with EKOF, can offer a holistic solution encompassing both flotation equipment and reagents. It is the only company in the world able to offer such a package. The association with EKOF strengthens the Humboldt Wedag product offering, especially as the company in-troduced pneumatic flotation cells to the South African market in the form of the PNEUFLOT®. Before starting pilot scale test work, a mineralogical analysis has to be carried out to determine the mineral com-position as well as the liberation grade. HW-CMT works together with independent institutes. Different reagent regimes can be tested in laboratory scale. Pilot machines, each packed in a 20? container, are available to carry out extensive test work at customers? processing plants. A group of engineers from HW-CMT is involved in the pilot test work. The flexible pilot machines are designed to cater for coal, ores and other minerals. The small feed rates of 7 ? 12 m³/h only means the pilot machines do not disturb the operation of process plants. Batch tests have to be carried out to determine the numbers of PNEU-FLOT® stages. New applications in iron ore, copper ore, platinum group minerals, rock phosphate and potash were suc-cessfully tested in the last three years. In applications where the feed material is very fine, PNEUFLOT® technology is able to achieve high recoveries with particle sizes where conventional technology failed.

Jan 1, 2007

By T. Szendrei, S. Tose

The generally accepted view in rock blasting is that the sources of energy for the fracture and movement of rock reside in the shock wave and gas action resulting from the explosion, and yet the mechanisms by which these sources interact with the rock have remained unclarified. It has also been noted that up to 50% of the work capacity of an explosive released in a blast cannot be accounted for by field measurements of energy partitioning. In this study, we describe a physical model that details the response of rock to both shock wave and gas action. An analytical model based on momentum conservation is derived to describe the dynamics of shock-driven expansion of the blasthole. Radial expansion of the hole is the key parameter that permits the derivation of the following characteristics of rock response to shock loads: hole expansion time; volume of displaced rock; energy consumed per unit volume; expansion energy efficiency; stress wave pulse length; gas pressure in enlarged hole. Soon after the completion of hole expansion, the shock wave degenerates to an elastic stress wave that runs through the burden. Blasthole expansions of between 50% and 300% of diameter are completed in under 1 ms and, depending on rock properties, consume 32% to 42% of the detonation energy or about 55% of the available mechanical (Gurney) energy. Gas pressure in the enlarged holes in five rock types is between 35 MPa and 650 MPa, and drives the mass movement of burden rock.

Oct 9, 2024

By I. Ashmole

The dimension stone industry is not widely known or appreciated within the mainstream mining industry. This is in spite of the fact that the industry has grown at an average of over 7% per annum since 1980, and is estimated to now have a global turnover in excess of US$ 60 Billion per annum. Production technologies, particularly in the developed world where labour costs are high, have developed rapidly over the past two decades. Aligned with this, there has been a significant trend in adoption of a more professional mining approach in the exploration for and operation of dimension stone quarries. In fact, in the experience of the authors, mining a dimension stone deposit successfully if often more challenging from a mining engineering point of view than many conventional surface mines. This paper gives an overview of the industry and then proceeds to discuss best practice in exploration for dimension stone and to outline the latest technologies applied in mining of dimension stone. These technologies are varied and the specific combination of technologies applied in any given quarry is determined by both the physical properties of the material as well as the influence of geology which significantly impacts on the recovery of saleable material and hence the economics of the quarry.

Jan 1, 2008

By P. L. Duncanson, J. D. Toth

Since 1995, when "freeze lining" refractory systems were introduced to the ferroalloy industry, they have gained in popularity, due to the freeze lining?s reputation for reliability, safety, and the contribution it makes to profitability. As with many popular and effective technologies, however, the freeze lining has spawned low-cost pretenders that claim the "freeze lining" name. On the surface they appear to contain some of the components of the technology, such as thermally conductive materials, but they fail to incorporate all of the principles that define a true Freeze Lining. The term "freeze lining" refers to the refractory system?s ability to maintain a temperature profile that is low enough to freeze a layer of process material on its hot face, which insulates the refractory and prevents direct contact with molten metal and slag. In doing so, the common wear mechanisms found in the submerged arc furnace - chemical attack, erosion, and thermal stress - can be prevented. These wear mechanisms are all related to high temperature; thus, they are prevented by maintaining low temperatures. Certain refractory properties and design concepts are absolutely necessary for the lining system to function as a true Freeze Lining. The paper explains these requirements and why they are important - the Truth of freeze linings - and further explains why systems that ignore one or more of these requirements cannot claim to be freeze linings, thereby exposing the Myths.

Jan 1, 2004

By G. A. Brown

Major mining projects are developed with the assistance of lending institutions who provide hundreds of millions of dollars in funding over several years, and of course expect those funds to be returned with interest. Two Australian banks have adopted the Equator Principles, an emerging financial industry benchmark for assessing and managing environmental and social risk in project financing. Project financiers have encountered environmental and social issues that are both complex and challenging, particularly with respect to projects in the emerging markets of Asia-Pacific and elsewhere. There are many recent and historical examples of failures by resource companies to effectively manage their environmental, social, safety and security risks, some of which have caused the project to fail completely, and some of which have caused the temporary cessation of production. These events put the financial institutions' funds at risk through inadequate management capacity and non-compliance adversely affecting the ability of the borrowers to repay the loans. They can also reflect adversely on the reputation of the lending institutions. In assessing these risks, lenders are increasingly looking at the track record of the borrower in its country of origin and in other countries where it operates. Lenders are wary of companies that have one standard for operations in a developed country, where the regulatory environment may tightly control what they do, and another standard for operations in countries where the regulatory regime is perhaps less stringent. Lenders may require environmental and social reviews or audits to be conducted on their behalf by competent third parties prior to a loan being approved, and annually over the life of the relationship. The mining industry's concept of the unwritten `social licence to operate' is highly relevant in relation to the delivery of community benefits that are sustainable post-mine closure. This paper provides examples of recent practices that support financial viability and sustainable development, as well as examples of some failures that have put lenders at risk.

Jan 1, 2007

By A. M. Hearn, J. R. Henning, A. S. J. Van Rensburg

The lining, together with the electrodes, forms the heart of the operation of a submerged arc furnace. Subsequent to a lining failure on M12 furnace during the early 1980s, Metalloys was active in investigating the concept of thermally efficient ?freeze? linings for its furnaces. The theory revolved around that, not only would, thermally efficient linings result in significant cost savings, but they would also last longer as a result of being subjected to less harsh operational conditions. After having proved the concept on the .smaller. furnaces, Metalloys decided to implement the concept on its largest submerged arc furnace, M12 Subsequent to having recovered from an impending failure of a lining installed in 1981 in M12 in the mid 1980s, Metalloys managed, through rigid lining management, to extend the life of this lining to 1999. At the end of 1999 the decision to replace the lining in the furnace with a ?freeze? lining was made and planning and design proceeded in earnest. This paper discusses the options considered in making the final decision. The features of the design of the lining are also discussed. Consideration is given to the furnace shell cooling system as a result of its importance in maintaining the thermal equilibrium in the lining. Note is made of the fact that the purchase of a .freeze. lining is an expensive exercise but that the time savings in the installation of the lining and the efficiency improvements during operation far outweigh the additional capital cost. The experience on M12 has been that the payback period of the marginal capital expenditure is less than three years. As a result of the opportunity to reline a furnace the size of M12 not presenting itself very often, the learning points from the installation of the lining and the operational advantages and disadvantages are significant. Finally, the point is made that the project had its pros and cons but overall the success of the project has been evident and, as such, the ?freeze? lining is likely to become the norm at Metalloys.

Jan 1, 2004

By R. Sullivan, K. Joiner, B. Emery, M. de Vries, F. A. Stober, L. R. Nelson, J. M. A. Geldenhuis

Keywords: Pyrometallurgy, smelting, converting, furnace design, furnace retrofit, high-intensity smelting, copper coolers, plate coolers, waffle coolers, tap-blocks, lower sidewall air-cooling, wall hold-down system, platinum group metals, ferroalloys, ferrochrome, ferrocobalt, ilmenite smelting, ironmaking, operational readiness, operational support The paper describes the development of furnace designs by Hatch in conjunction with the smelting plants in Africa to meet the intense process requirements in certain applications; continued improvement in operating efficiency through increased throughput from existing crucibles; and improvement in campaign life and furnace integrity. The era of Hatch in Africa has seen the doubling of furnace power in retrofit projects using existing crucibles to developing the highest intensity immersed electrode operations in the world. This has resulted in minimized OPEX and CAPEX per unit of production. Through the continued development of its cooling, binding and furnace power supply technologies and working with the experienced and knowledgeable personnel at the smelting facilities in Africa, Hatch has managed to meet the challenges of ever increasing furnace process requirements associated with increased power density and superheats prevalent in the operations. In addition to developing furnace crucible designs, Hatch has also intensified its ?after sales service and support? with the construction, commissioning and start-up technical assistance and operational readiness and operational support for ramp-up to nameplate capacity and beyond. The key areas of furnace risk associated with high superheat molten material tapping has also seen the development of diagnostic systems to mitigate risks and produce early warning signals for the operators.

Jan 1, 2006

The kinetics of cyanide loss were found to be first order under any given set of conditions, allowing rate constants to be easily determined. At room temperature and in the absence of activated carbon, some cyanide is lost by hydrolysis to hydrogen cyanide, but this does not occur to any significant extent at pH values higher than about 10. A higher rate of hydrolysis occurs when air agitation is used. When activated carbon is present, an additional carbon-catalysed oxidation reaction is responsible for a fairly high loss of cyanide. The evidence indicates a reaction mechanism that consumes oxygen and produces cyanate ion. Some of the cyanate thus produced decomposes to form a mixture of ammonia, carbonate, and urea, depending on the solution conditions. Additional cyanide is lost as a result of the adsorption of sodium cyanide by the activated carbon. At high temperatures, an additional hydrolysis reaction, which involves the formation of ammonium formate as an intermediate, occurs an/j is responsible for. a high loss of cyanide, leading ultimately to the formation of ammonia, hydrogen, and carbon dioxide. The presence of activated carbon has no effect on the rate of this reaction.

Jan 1, 1990

By M. Arnesen

Mining professionals recognize the need to continuously evaluate and refine mine planning standards and scheduling. We must examine our current reality, and evaluate the following: •How well do our planning standards represent the actual mining process? •To what extent do they support the requirements of the downstream mining activities? •How we apply them to operational management and control? In most operations, mine-planning standards are global averages. Little differentiation is madein quantifying key planning variables. Often standards used in the long-term, are applied to the short-term, and the standards and scheduling precedents are only reviewed occasionally. Mine-planning standards applied to production schedules are often only focused on the management of functional mining performance, and play no role in managing the requirements of down stream processing. Many mining operations are characterized by high levels of fluctuation, and typically incorporate a wide range of factors and adjustments to compensate for deviations from performance targets, in mining operations as well as for the other business areas. The reason for using global averages is because of a lack of understanding of the causes of deviations that occur through the process, and the impact that they may have on the performance of the business as a whole. Average standards and factors are often used to quantify the variability in a system. From these average values, measurement standards and performance targets are derived for the planning and execution environments. During the execution of a plan/schedule there will be deviation in actual performance and the planned ‘average’ standards. In reality the ‘average’ conditions seldom occur and the impact of variability and interdependency are seldom constant or predictable. The predictability of variability and interdependency is further complicated by the fact that mining conditions have a role to play in the actual production performance, and they too are variable. By developing the throughput knowledge of our production systems, we can better understand the nature of variability and the interdependency within the systems as well as the impact of interdependency between the links in our production chains. With this knowledge, planning standards and scheduling precedents can be better defined and sensibly differentiated. This will improve planning and management of ore utilization, mining production and the effectiveness of processing. As a result the business will be more stable and predictable and business performance will be improved. The purpose of this paper is to describe: •At a high level, the scope for refining and differentiation in mine planning standards, and incorporating geological and plant parameters into mine scheduling. This will improve planning and scheduling and the overall performance of the mine. Given our current level of scientific knowledge and the technological tools at our disposal we should be able to plan and schedule production so that we can manage pro-actively and improve business performance. In doing so we can also improve reconciliation and value tracking through mining and processing •The flexibility and functionality of the XPAC planning and scheduling tool that will enable a throughput management approach.

Jan 1, 2003

Palabora Mining Company is operating a copper block cave mine in the Limpopo Province of South Africa. The mine was developed in the late nineties with a target ore reserve of 220 million tonnes of carbonatite at 0.69% copper. At 30,000 tonnes per day the operation had an estimated life of mine of approximately 23 years. Cave induced open pit side wall failure occurred in late 2004 with 130 million tonnes of waste reporting to the bottom of the open pit. This failure resulted in potential sterilization and dilution of the ore reserve and subsequent reduction in life of mine. Physical and numerical modelling indicated potential losses of up to 30% of the original ore reserves. Cave Management tools based on throughput principles are utilized to manage the failed waste ingress and ensure an optimum life of mine. Extracting the maximum rate possible, as soon as draw points are commissioned, with the view of achieving the highest production in the short term, is any mining operation?s goal as more money is required sooner. This approach, of course, improves the cash flow but presents a risk in the cave propagation profile as overall draw control is compromised. At Palabora it is evident from a Mineral Resource Throughput Management (MRTM) point of view that maximum production in the short term is not the solution. If high production rates are achieved and the profile of the cave is not manage correctly, this results in failed waste reporting to draw points earlier with adverse effects on grade. This would effectively and significantly shorten Palabora?s Life of Mine. The applications of good MRTM principles are required to assist the value chain for sustained profitability. The process commenced with change management paving the way for a better understanding and a holistic view for all role players.

Jan 1, 2007

By R. L. Castro

The extraction of ore in panel caving operations also involves the coextraction of non-economic material, known as dilution. Forecasting, avoiding, and understanding the mechanics of dilution is critical to longterm planning. The models of dilution that are currently in use in panel caving operations are those by Laubscher (1994), who postulated that dilution is due to gravitational flow and depends on the height of interaction, the column height, and the draw uniformity. This paper presents a back-analysis of extraction and dilution behaviour at Codelco?s El Salvador and Andina Divisions, which use panel caving as a mining method. This analysis was conducted in order to review the existent dilution entry mechanisms and calculation methods. Three sources of dilution were identified. The first source is ?gravitational dilution?, which is due to gravitational flow and mixing as dilution migrates by gravity from a sector located above the panel under analysis. The second source of dilution is ?caving dilution?, which occurs when an air gap is formed in a large area and a sudden propagation of a hang-up occurs, inducing early ingress of waste into the production level from a level above. The third mode observed is ?lateral dilution?, which occurs when the panel is located next to an exhausted sector and the broken material enters the draw column early during draw. In the last two cases, dilution could migrate large distances horizontally. The mine data indicated that draw and caving strategy are key for long-term planning of large panel caves.

Jan 1, 2014

A201 aluminium alloy is a high strength casting alloy with a nominal composition of Al-4.6Cu-0.3Mg-0.6Ag. It is strengthened by the O(Al2Cu) phase and the ??(Al2Cu) phase during heat treatment. Further strengthening of this alloy system can be obtained through the addition of transition elements, but care must be taken as other elements might have adverse effects on the mechanical properties. The objective of this study is to determine the influence of Mn on the tensile properties of rheo-processed Al-Cu-Mg-Ag alloy A201. ThermoCalc software was used to predict the different phases that can be expected in the alloys, and scanning electron microscopy(SEM) with energy dispersive spectroscopy (EDS) was used to investigate the actual phases that formed. The influence of these phases on tensile properties is quantified. SEM and ThermoCalc revealed that there is an increased amount of the Al20Cu2Mn3 with increasing Mn. The tensile properties showed that high amounts of Mn do have adverse effects on the tensile properties of alloy A201, especially the ductility. Keywords Semi-solid metal (SSM) forming, alloy A201, intermetallics, Al20Cu2Mn3

Jan 1, 2011

By M. Grave

Rock Engineers are required to design safe cost effective support systems and stoping layouts for their respective mines. As each stope has its own unique environment, continual re evaluation is required in all stopes to maximize extraction and achieve value from the support standard. This paper presents numerical modelling used to plan early mining within the shaft pillar and a reevaluation of an existing stope support standard.

Jan 1, 2009

By J. Bullón, A. Pérez

Some years ago, Ferroatlantica developed a new type of electrode known as the ELSA electrode. In this electrode there is a central graphite core that provides support, surrounded by an annulus of Søderberg paste that gets baked during operation. This technology has been implemented on several silicon furnaces around the world, and was reported on during the previous Infacon conference. In all electrodes, but particularly in the ELSA electrode, the quality and consistency of the paste are important for correct operation. As the type of paste varies between customers and between countries, Ferroatlantica has developed a quality control procedure for their customers of this technology. This procedure is geared to the point of view of the customer rather than the paste producer. The analysis is based on the desired flow pattern of the raw paste and on the desired mechanical and electrical properties of the baked paste, as experience has shown that these are the most important parameters to monitor in order to avoid having problems with the resulting electrodes. This paper discusses these methods of paste analysis in the light of complementary studies that have been done when there has been an electrode breakage in the different plants.

Jan 1, 2007

By V. Miguel-Silva, B. C. Afonseca

Drill-hole spacing analysis (DHSA) and optimization are becoming commonplace for uncertainty assessment and management in the mining industry. However, there is no standardized DHSA workflow, and the outputs of certain methodologies are not interchangeable. We group available simulation-based DHSA methods according to their accounted uncertainty into (i) raw uncertainty, assessed by drawing realizations from synthetic data-sets with the drilling spacings to be tested; and (ii) model uncertainty, in which these synthetic data-sets are used to assess the variation between the estimated model and the (unknown) actual value. DHSA workflows available in the literature ignore the differences between both types of uncertainty. Commonly, the DHSA algorithm is chosen without a detailed analysis of its uncertainty output, which may lead to misleading results and suboptimal decisions. While available solutions are based only on assessing raw or model uncertainty, the proposed approach simultaneously analyses both and their relationship for models at different stages of the mine. The integrated analysis results deliver more information to support decision-making than available methods. Principles, practical considerations, and discussions of the advantages of the proposed integrated analysis are presented. The approach is applied to a real gold deposit to illustrate its use.

Jun 2, 2022

By J. Searra, M. Aboagye

"For new mining projects or for medium- to long-term areas of existing mines, drilling data is invariably on a relatively large grid. Direct estimates for selective mining units (SMUs), and also for much larger block units, will then be smoothed due to the information effects and the high error variance.The difficulty is that ultimately, during mining, selection will be done on the basis of SMUs on the final close-spaced data grid (grade control), which will then be available, i.e. the actual selection will be more efficient, with fewer misclassifications. However, this ultimate mining position is unknown at the project feasibility stage and therefore has to be estimated. This estimation is required because any cash flow calculations made on the basis of the smoothed estimates will obviously misrepresent the overall economic value of the project, i.e. the average grade of blocks above cut-off will be underestimated and the tonnage overestimated for cut-off grades below the average grade of the orebody. Similarly, unsmoothed estimates will be conditionally biased and will give even worse results, particularly in local areas of short- and medium-term planning or mining.This paper presents a case study of indirect post-processing and proportional modelling of recoverable resources designed for mediumand long-term mine planning at the Gold Fields’ Tarkwa Mine in Ghana. The case study compares long-term indirect recoverable mineral resource estimates based on typical widely spaced feasibility data to the corresponding production grade control model as well as the mine production. The paper also proposes certain critical regression slope and kriging efficiency control limits to avoid inefficient medium- to longterm recoverable estimates, and highlights the danger of accepting block estimates that have a slope of regression less than 0.5."

Jan 1, 2015

Rock mass classification systems are extensively used in rock engineering design work, and mine design is no exception. Among the systems most widely used for mining-related design work are the NGI 0-system (Barton et al., 1974), the RMR system (Bieniawski, 1976), the MRMR system (Laubscher and Taylor, 1976) and, more recently, the GSI system (Hoek et al., 1998). Classifying the rock mass is widely seen as being the fieldwork required to characterize the rock mass and enable the application of empirical design methods associated with the different classification systems. This paper argues that it is fundamentally important to recognize the distinction between rock mass characterization and rock mass classification. These two processes should, in most cases, be separated from each other. Rock mass characterization should be used to determine the intrinsic properties of the rock mass independently of the application; i.e. independent from the infrastructure to be designed, the size, shape, and orientation of the excavation(s) or pillar(s), etc. Rock mass characterization should also be compatible with most classification systems and empirical design methods to be used. Rock mass characterization is the background fieldwork required to perform rock mass classification and/or engineering design work. Rock mass classification is the subsequent step to the characterization, and an integral part of the design process. Parameters that vary according to the design, such as the relative orientation of geological structures compared to the opening or the mine-induced stresses, should be calculated as part of the rock mass classification and design process, rather than during the rock mass characterization process. The failure to distinguish between rock mass characterization and rock mass classification can lead to major design errors and poor results.

Jan 1, 2012

By M. Mbonami, R. Pretorius, J. Miller, P. Kyony, B. Nel, N. Mautsa

Challenges due to the formation of stable froth in acid leach systems is common at many copper and Ccbalt producers. Stable froth affects downstream process, critical equipment, and operational parameters. In severe cases the froth present safety and environmental risks and increased operational costs. Solids reports in the pregnant leach solution, accumulates, and clogs launders resulting in a potential costly safety and environmental risk. Solvent extraction is operationally affected by crud formation, organic solvent and extractant losses, reduced mass transfer due to the solids carried downstream. This article reviews the generally inadequate mechanical and hydraulic solutions of froth elimination employed over the years. The recent introduction of a chemically based solution able to eliminate froth problems that can potentially turn around the situation for those who adopt the technology.

Jan 1, 2023

By R. J. Dippenaar, J. C. van den Berg

This paper describes an investigation into the prereduction of hematite fines in a fluidized-bed reactor as a means by which they can be prepared for direct smelting in a transfered-arc plasma furnace. A single-stage fixed fluidized bed reactor using the in situ gasification of coal was employed. It is shown that the hematite is reduced to magnetite at 1000 QC, the degree of reduction being limited by the inherent shortcomings of a single-stage reactor in which both the gasification and the reduction reactions have to occur. Methods by which the degree of reduction can be increased are suggested. The gasification process was studied in some detail, and three different reducing agents are compared. The dominating effect of the Boudouard reaction on the behaviour of the fluidized bed is clearly illustrated. Non-coking coals of high reactivity are best suited to this process, a finding that would complement the trend away from coke as a metallurgical reducing agent.

Jan 1, 1989