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By Noel C. Joughin

In making judgements on tolerable levels of risk in industry, and in all spheres of life, it needs to be understood that every action gives rise to risk. Without risk, nothing can be done. Without risk, no economy could be advanced. There is a strong tendency to emphasize the risk at work, but persons who are not working are exposed to a different set of risks. Often persons who are not working face greater risks than persons who are working. Simply, in being alive, one is exposed to the risk of an accident, the risk of contracting a disease, and an extremely diverse variety of other risks. According to the Health and Safety Executive of the UK, it is not possible to have a state of zero risk, because ?a state of zero risk does not exist?. Because zero risk is a physical impossibility, it is not possible to design for a state of zero risk in all engineering design. While the strategic target of achieving zero risk is laudable it does not provide any practical guidance to engineers as to what acceptable limits of risk should be. This causes a significant and real problem in the design for and the management of risk. Without meaningful guidelines, engineers, managers and the authorities often find themselves in disagreement. Thus, it has become essential to establish criteria for tolerable levels of risk and unacceptable levels of risk in order to design and manage engineering systems properly.

Jan 1, 2011

By M. L. Bakker

Keywords: Pyrometallurgy, top submerged lance (TSL), nickel, PGM, calcium ferrite, lime ferrite The ISASMELT? top submerged lance (TSL) bath smelting process was developed in Mount Isa, Australia by Mount Isa Mines Limited (now a subsidiary of Xstrata plc) during the 1980s. By the end of 2011, the total installed capacity of the ISASMELT? technology will exceed 9 000 000 metric tons per year of feed materials in copper and lead smelters around the world. Commercial plants, operating in Belgium and Germany, are also batch converting copper materials in ISASMELT? furnaces. This TSL technology is equally effective for continuous converting processes, whereupon it is called ISACONVERT?. This paper presents the recently patented ISACONVERT? process for the continuous converting of nickel and Platinum Group Metal (PGM) containing mattes using the calcium ferrite slag system. The paper focuses on the potential application of the ISACONVERT? technology to existing nickel and PGM smelting complexes.

Jan 1, 2011

By R. C. D. Phillis

The management of critical resource inventories is an important productivity lever and a significant risk factor?risk in the sense that poor resource availability lends itself to disempowerment of workers, unsafe work practices, wasted spending (high unit costs),and poor quality of work (including mining waste/rework). Most underground platinum mines experience lost blasts that directly lead to reduced productivity. In most surveyed shafts, 30% of lost blasts can be attributed to shortages of critical material and/or equipment. The problem is prevalent despite the existence of conventional transitory surface and underground stores. This paper discusses the introduction of buffer stores as a complementary materials storage system in order to improve health and safety in mines as well as reduce lost blasts. Both quantitative and qualitative results have shown that buffer stores result in dramatic improvements in productivity and are readily acceptable by stakeholders. Keywords Buffer stores, lost blast.

Jan 1, 2011

By E. S. Schubert

Keywords: co-generation, furnace CO-gas cleaning, disintegrator scrubber, Theisen In a closed, electric, reduction furnace, no oxygen enters the furnace from the surrounding environment. The off-gases are thus not ?burnt? and therefore contain a considerable amount of CO and H2. Traditionally these gases have been captured and burnt in a flare stack. Recent developments have led operators of such furnaces to revise this strategy and to consider utilising these gases as a fuel for gas-fired generator sets to produce electricity, thus becoming more energy efficient. On 31 March 2010 the new emission standards, in accordance with the Air Quality Act, Act 39 of 2004, were promulgated. The minimum emission standards according to the act require that the particulate matter emissions from the primary fume-capture systems on closed furnaces for ?new plants? in ferroalloy and calcium carbide production not exceed 50 mg/Nm³ and 25 mg/Nm³, respectively. By implementing co-generation, the producer automatically complies with the new environmental emission standards for an off-gas. As much as 30% of the electrical power cost, which is set to double in the near future, can be saved by partly generating one?s own electrical power. In December 2010, the National Treasury published a discussion paper for public comment, one entitled ?Reducing greenhouse gas emissions: The carbon tax option?. Irrespective of how the tax is finally implemented, it will result in an increase of production costs in affected industries. This paper focuses on the characteristics of a furnace-off-gas cleaning system for closed ferroalloy smelters, characteristics that meet the requirements of both reducing solid-matter emissions and operating a safe and reliable gas plant.

Jan 1, 2011

By D. S. van Vuuren

Industrial production of titanium occurs via the batch-wise reduction of titanium tetrachloride (TiCl4) with a reducing metal, being magnesium in the Kroll process, or sodium in the Hunter process. In the search for low cost titanium, the CSIR is developing a continuous process to produce titanium powder directly via metallothermic reduction of TiCl4 in molten salt, dubbed the CSIR-Ti process. The move to a continuous process has been attempted by a number of organizations, but was until now always met with failure, due in no small part to challenges inherent in the process chemistry. The reaction between TiCl4 and the reducing metal can occur directly, when TiCl4 or any titanium sub-chlorides present, comes into contact with suspended or dissolved reducing metal. The reaction can also occur indirectly, without any physical contact between the reacting species, via an electronically mediated mechanism. The reaction mechanism via electronic mediation can cause TiCl4 to react at the outlet of the feed port, rapidly causing blockages of the TiCl4 feed line. The electrical conductivity of the metal reactor can also cause the electronically mediated reaction to favour the formation of titanium sponge on the reactor walls and internals, rather than titanium powder. Various methods were investigated to overcome the problem of blockages in the TiCl4 feed line, e.g. mechanical removal, sonic velocities, dilution of the TiCl4 and the use of ceramic feed lines. This article discusses problems experienced with the continuous feeding of reagents, and various methods attempted are shown and discussed. Information is also given on the morphology, chemical composition and suitability of the final titanium powder for powder metallurgical application as presently produced by the CSIR-Ti process. Keywords Titanium dioxide, titanium nitride, carbo-thermic reduction, ilmenite, slag, tunnel kiln, residence time.

Jan 1, 2011

By S. O?Connor

When one looks back and does assessments of what has been the key ingredient in achieving success in our safety efforts, there are many issues that spring to mind and cover a wide array of elements. One does not know which has the ultimate maximum effect. In his presentation yesterday, Alan Peers, our SHEQ leader, covered a lot of detail with the way we are managing safety at Modikwa. I have attempted to identify some of the key essentials in making the mine safe. Passion Safety is addressed with a passion that is unbelievable at times. When I get phoned because an incident has occurred and in reporting the incident, there are already action plans being put in place to prevent re-occurrences, you understand the commitment to put employees? safety first. You hear the disappointment in your subordinates? voices when they have to share the fact that an incident or accident has occurred.

Jan 1, 2011

By Willem Le Roux

The common law requires an employer to take reasonable steps for the safety of employees. In general, the duty of care means that the employer, acting personally or through its employees or agents, must take reasonable care for the safety of its employees (Van Deventer v Workmen?s Compensation Commissioner; 1962 (4) SA 28 T; Oosthuizen v Homegas (Pty) Ltd 1992 (3) SA 463 T).The duty of care includes the provision of safe premises, safe machinery and tools and a safe system of work. The obligation is not an absolute one, but is restricted by the concept of reasonableness. The common law duty may, in certain cases, include the assessment of hazards and risks. 2 International law Great emphasis has been placed in the Western world on the prevention of occupational diseases and injuries. Detailed statutes and regulations govern specific industries in many countries. See, e.g. the Control of Substances Hazardous to Health Regulations of the United Kingdom and various regulations applicable to the use of asbestos and lead, fire protection, mines and quarries, petroleum, etc. Risk management is an important part of managing health and safety. In the United Kingdom, the Management of Health and Safety at Work Regulations, 1999, require every employer to make a ?suitable and sufficient assessment of the risks to health and safety of his employees to which they are exposed whilst they are at work?. The particularity of the assessment is determined by the risk in question.

Jan 1, 2011

By J. L. Viljoen

t has long been the drive of the industry and all operations to create an environment that is free of injury and illness. We have come a long way; the leaders, executives, managers, supervisors and workers are to be commended for relentlessly driving to create, what I call a ?White Flag Day Every Day?. Yet I am also aware of the huge shift we still need to create in the industry, on the operations and in the workplaces to have them free of injury and illness. Keywords People, values, care, trust, belief.

Jan 1, 2011

By M. D. Raganya

The Kriel Colliery is an Anglo Coal mine which is contracted with Eskom to produce No. 4 seam for Kriel power station. The mine previously found it uneconomical to mine No. 5 seam due to the low qualities and tonnages of the seam, both at the opencast and underground sections. An area has been encountered for the first time at Kriel Colliery opencast pit 5, where the tonnage and qualities of No. 5 seam warrant further investigation. The primary reason for the investi¬gation of No. 5 seam by Kriel Colliery is because of the advantage of the high selling price (R450/t) that the market is currently prepared to pay for the No. 5 seam. The aim of this project is to mine No. 5 seam economically without interrupting No. 4 seam mining operations. The problem is that the equipments that are currently being used at the mine belong to Eskom and are dedicated to mining No. 4 seam only, not No. 5 seam. Through geology investigation, it is found that the whole No. 5 seam (No. 5 seam upper and lower) has an average thickness of 1.8 m. It also contains a parting of carbonaceous shale which divides the seam into two parts. No. 5 seam upper contains less tonnage compared to No. 5 seam lower. The calorific value and ash content of No. 5 seam lower is far better than No. 5 seam upper, but would still require washing the coal. This makes No. 5 seam lower the preferred seam to mine because it meets the requirements of the customer which is Highveld Steel. It is a coincidence that the area containing No. 5 seam under investigation encounters high overburden problems. The problem of drilling to No. 4 seam was going to be encountered because the thickness of the overburden ranges from 35 to 39 m. The Gardner Denver at the mine can drill blastholes only to a depth of 34.5 m, meaning the full overburden will not be drilled at once. This means the mining of No. 5 seam will do favours for Eskom because the overburden thickness will be minimized. This then led to an agreement between Anglo Coal and Eskom to mine No. 5 seam because both companies benefit from the project. In order to identify a suitable mining method for No. 5 seam lower, literature studies took place. It is found that San Juan mine from the USA has similar geological features to Kriel Colliery's No. 5 seam. Through comparisons, it is found that truck and shovel mining would suit the geology of Kriel Colliery's No. 5 seam since San Juan mine is using it. The sequence of mining No. 5 seam lower allows for a clearance of two cuts between the truck and shovel operation and the dragline. The mining sequence of No. 5 and 4 seam will be in the order of top soil removal; soft overburden pre-stripping; pre-strip drilling; pre-strip hard overburden; No. 5 seam lower coaling; interburden drilling and blasting; interburden stripping and No. 4 seam coaling. Financial evaluation of the project shows that a contractor will charge Kriel Colliery (Anglo Coal) approximately R 102.2 million to mine No. 5 seam successfully. The sales of No. 5 seam lower will provide a profit of R99.4 million at a yield of 70% from the washing plant. The project is beneficial to both Eskom and Anglo Coal because Eskom will have eliminated the problem of pre-stripping and Anglo Coal will generate additional profit. Through investigation and analyses of the project, it is proven to be viable and should take place. This is after looking at the advantages that the project has for Anglo Coal and Eskom. Keywords No. 5 seam, truck and shovel mining, Kriel Colliery, No. 5 seam mining at Kriel Colliery opencast, Anglo Coal and Eskom, No. 5 seam upper and lower, top soil removal, soft overburden pre-stripping, pre-strip drilling, pre-strip hard overburden, No. 5 seam lower coaling, interburden drilling and blasting, interburden stripping, No. 4 seam coaling.

Jan 1, 2011

The optimum cut-off grade policy maximizes the net present value (NPV) of an open pit mining operation subject to the mining, processing, and refining capacity constraints. The traditional approaches to cut-off grade determination ignore the escalation of the economic parameters such as metal price and operating costs during life of an operation, and consequently lead to unrealistically higher values of the objective function. Further, the NPV of a mining operation declines due to the depletion of the available reserves, causing a decline in the optimum cut-off grade, i.e. higher cut-off grades in the early years of an operation and lower cut-off grades during the later years. Hence, low grade material mined in the earlier years may be stockpiled for processing during later years to offset the effect of escalating economic parameters on NPV. This paper demonstrates the combined impact of introducing economic parameters, escalation and stockpiling options into the cut-off grade optimization model. The model promises an enhancement in NPV as illustrated in a case study incorporating practical aspects of an open pit mining operation.

Jan 1, 2011

By M. Ksiazek

Keywords: Thermal conductivity, thermal diffusivity, flash method, specific heat capacity, manganese ore Manganese ferro-alloys manufacturing involves a combination of quality raw materials and an energy source to produce high-quality products with low energy consumption. The thermal properties of manganese raw materials such as ores, sinters, and briquettes, are among the many factors that determine the amount of energy needed for processing. Thermal expansion, thermal diffusivity, conductivity, and apparent specific heat capacity of solid samples and compacted powder samples of manganese ores were examined from room temperature to 1000 °C. The effect of porosity (of the materials used) on the thermal properties was also investigated. The laser flash method and a pushrod dilatometer were used.

Jan 1, 2011

By F. T. Cawood

This article offers a personal and independent view on the threats to the sustainability of the South African minerals industry. It argues that if the six identified threats of insufficient spending on research and development, general standard of education, nationalization, inadequate infrastructure, Aids prevalence and labour inefficiency are not acted upon as a matter of urgency, the future of the mining industry, along with its important contribution to the economy, is at risk.

Jan 1, 2011

By R. Webber-Youngman

The Department of Mining Engineering at the University of Pretoria accepts that the process of teaching and learning improvement is an ongoing exercise with the ultimate aim to deliver well-rounded mining engineering practitioners. Various challenges impact on the success of this process. An integrated and innovative process was developed and is followed in the Department to overcome these challenges. The aim of the Department is to apply a holistic teaching approach by introducing multiple integrated interventions with regards to teaching and learning strategies. Three phases of this process are discussed in this article, and are illustrated in Figure 1. During the first phase, prior to 1999, several teaching and learning challenges were identified in the Department of Mining Engineering. These challenges are discussed in the next section. In the current phase, a variety of interventions to address the challenges are being developed, implemented (in some cases piloted), and evaluated. The future phases will focus on the improvement, successes, and full roll-out of current interventions, as well as on training, development, and support for all staff members to participate in the process. (Figure 1)

Jan 1, 2011

By M. Ericsson

?Rare earths ?will not be bargaining instruments?? was stated in a headline in China Daily of 29 October 2010. The Chinese government is trying to fend off the persistent accusations from Japan, the USA, and Europe that it is manipulating the supply of these so called ?critical? metals to gain political and economic advantages. The critics maintain that China has taken the rest of the world hostage by controlling 97% of the resources of rare earths. These elements are crucial in a number of high-tech applications. They are not impossible to substitute, but difficult to do so effectively. The name ?rare earth? is a misnomer, as even the least abundant is 200 times more common in the Earth?s crust than gold. They are, however, difficult to find in economic concentrations. The Chinese near-monopoly over the rare earths, together with China?s scramble for other resources in Australia, Africa, and elsewhere around the world, is seen as an example of a Chinese strategy to take control of vital metal resources. The Chinese are also accused of using unfair and sometimes illegal business practices in this fight for resources. Practices which, critics claim, put the Chinese interests above the interests of the host countries, in particular in Africa.

Jan 1, 2011

By S. J. Oosthuizen

This paper examines innovation in relation to the availability of anew material: the metal titanium. The paper aims to highlight the need for the inclusion of entrepreneurial innovation as a necessary focus area in the development of a titanium metal value chain. Both the Department of Science and Technology (DST) and the Department of Mineral Resources (DMR) have identified the creation of titanium metals production capabilities as a key growth area for South Africa. Using historical literature as a source of data, the activities of selected innovators who used titanium metal as a central component in their success, were investigated. The origin of the process innovation behind the titanium metals industry, and two titanium product innovations: namely, medical implants and sporting goods, were detailed as case studies. It was found that individual innovators were responsible for the creation, and rapid growth, of the titanium industry and titanium product applications. There is a need to link the current research and development into titanium metals production with individuals and organizations capable of commercializing innovative processes and products.

Jan 1, 2011

By B. P. Watson

The discussion written by Dr de Frey suggests that mine design should be based on closely spaced stability pillars. However, this concept leads to low extraction ratios at depth. The concept of `crush' pillars in conjunction with more widely, appropriately spaced stability pillars allows for significantly larger extraction ratios, particularly at depth. It should be noted that the rock conditions in many areas of South African platinum and gold mines are good, allowing significant spans to be mined safely between stability pillars. `Crush' pillars are cut small enough to fail stably near the face under stiff loading conditions, and their residual strength is intended to support about 10 m rock height between stability pillars. While this support resistance cannot be achieved by conventional support, crush pillars have been proven to have the required capacity for this purpose. The concept of leaving smaller crush pillars with appropriately positioned stability pillars has been used successfully for more than 30 years in areas of South African platinum and gold mines.

Jan 1, 2011

Mining executives often have a difficult task determining what the strategic objective of the business should be as this can be impacted by the prevailing market conditions. In addition, they have no mechanism to quantitatively 'test' the impact of this strategic decision on the business and understand the underlying dynamics. During the commodities bull run of 2003 to 2008 the strategic objective may have been to grow the long term value of the business (NPV) through increased tonnage, acquisition and finding new reserves, which all came with an increasing fixed cost base. Now with the financial crisis upon us and the collapse of commodity prices and demand, executives have adjusted their strategies as 'cash is king' and short-term cash flow, in some instances at the expense of long terms value, is the order of the day. For many mining companies, mine closures, reductions in production and cost cutting exercisers are now the focus. In many instances, management do not have an ability to rapidly test different strategic alternatives to 'test' the impact on value, unit costs, reserves and profitability at the operational level and optimize the underlying trade-off variables. Economic modelling of the complete business value chain is a means of linking the operational 'reality' and strategic choices, so that the full impact can be assessed. This paper describes some of the challenges facing mining executives and how economic modelling can be applied to make decision making more rigorous.

Jan 1, 2010

By F. P. Greyling

The aspect of sustainability of ferroalloy processes has long been a serious matter for consideration in many of the world?s industrialized countries. A number of countries can be named where ferroalloy plants that were once flourishing, have all but disappeared. One of the most important factors playing a role in this type of occurrence is the cost and availability of quality raw materials. Given that all natural resources will be depleted with time, users are compelled to develop new processes that are sustainable in the changing environment. The DC arc smelting furnace is one such process that has proved itself, and has gained increasing popularity over the past two decades. This process, amongst other benefits, directly addresses the use of more readily available and more affordable raw materials in ferroalloy production. Since early in the new millennium, GLPS has been involved in various studies for different clients of furnaces for the production of ferroalloys. Two of these recent studies have culminated in the design, construction and commissioning of DC arc furnaces for the production of ferrochrome. One of these furnaces is a 10 MW unit at Mogale Alloys, and the other a 60 MW unit at the Middelburg plant of Samancor Chrome. This paper discusses the approach taken in the design and construction of these two furnaces, which, although varying significantly in size and capacity, are very similar in many other aspects of their design. Keywords Furnace, DC arc, and ferrochrome.

Jan 1, 2010

Geologists in some underground gold mines collect grab samples from broken ore piles or trucks as a method of grade control. It is often known as muck sampling. Generally, the goal of grab sampling is to try and reconcile the mined grade at the ore source to the predicted grade and/or predict the mill feed grade. The mass of the sample collected is limited by health and safety issues, as well as by the capacity of the laboratory to process the samples within a given time frame. In general terms, grab sampling is known to be problematic because samplers tend to oversample the fines, and/or pick out high-grade fragments; surface sampling of piles does not test material within the pile; muck piles in development drives/faces are likely to be zoned due to the blasting sequence; high or low-grade material may preferentially segregate in the pile during mucking; the five per cent mass reject size of the material in muck piles is very large from underground blasting; some correlation usually exists whereby the larger fragments are enriched or depleted in the critical component of value; and the average error made in estimating the true stockpile grade is likely to be high. The method is prone to chronic fundamental sampling, grouping and segregation, delimitation, and extraction errors. Substantial warnings must be given about the use of grab sampling for grade control in gold mines. The method may appear to work sometimes, which can be attributed to a fine gold particle sizing and more disseminated distribution. As with all sampling methods, its appropriateness must be determined by ore characterization and heterogeneity testing to ensure the method suits the ore type.

Jan 1, 2010

By C. -J. Rick

By implementing a converter downstream of the reduction furnace it is possible to broaden the product range significantly. The converter can also successfully be used to strip furnace slag from chromium oxide. Some process alternatives and their economical, practical and environmental implications are studied using process models developed based on UHT?s long experience in stainless steelmaking, stainless steel process control and charge chrome refining. Keywords Charge chrome, converter refining, ferrochromium products, process design.

Jan 1, 2010