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By Kurt Oakes, Paul Worsey, Braden Lusk, Tony Brasier, Jerry Chambers, Scott Crabtree, Randy Wheeler

Destructive wave interference has been studied in theory for many years. In application however, limited information can be found. Recently, circumstances have enabled a multidisciplinary team to utilize electronic detonators and seismograph analysis to create destructive wave interference in an underground production blasting application. Springfield Underground, located in Springfield, MO, in conjunction with Orica, ETI, White Industrial Seismology, and the University of Missouri – Rolla has shown the ability to use destructive wave interference in underground blasting to reduce ground vibrations directly above.

Jan 1, 2006

By E. A. Roux

As the first mine-to-metal zinc operation utilising atmospheric leaching, solvent extraction and electrowinning, Skorpion Zinc faces unique challenges and opportunities. One of these challenges is found in the solvent extraction circuit, in which di-ethylhexyl phosphoric acid (D2EHPA) is used as the organic extractant. Although D2EHPA is an excellent extractant for zinc, it suffers from the co-extraction of ferric iron, which is produced during leaching and by the corrosion of the grinding media. This situation is partially mitigated by iron precipitation in the neutralisation step prior to solvent extraction. Unfortunately, some ferric iron still reports to the solvent extraction process. This leads to a slow build up of iron in the organic phase. Chemical stripping is used to maintain the Fe concentration at an acceptable level. In this paper, the efficiency of the iron removal process is discussed.

Jan 1, 2006

By I. Lackey

In 2004, Zinifex Budel Zink commenced testing with the objective to increase the precipitation of aluminium in the iron purification stage of its hydrometallurgical zinc circuit, without the use of expensive reagents. Findings from the literature applied to the leach circuit at Zinifex Budel Zink demonstrated that aluminium removal from the leach circuit could be increased by lowering the ferric concentration and acidity in the vessels where jarosite precipitation occurs. An associated increase in copper precipitation was mitigated by limiting the extent to which the ferric concentration was lowered in the vessels where jarosite forms and lowering the ratio of copper to aluminium in the solutions entering these vessels.

Jan 1, 2006

By Chelsea Woodward

The Spokane Research Laboratory of the National Institute for Occupational Safety and Health has demonstrated a prototype hydrogen-fueled mining vehicle as an alternative to diesel equipment in underground mines. Safety and control systems were added to allow a 70-kW rubber-tired hydrogen vehicle, originally developed by the U. S. Bureau of Mines and Hydrogen Consultants, Inc. (now Hydrogen Components, Inc., of Littleton, CO), to be tested. This work began in late 2000 and culminated with a Mine Safety and Health Administration fire safety review and field tests at the Stillwater Mine in Nye, MT, in 2004.

Jan 1, 2006

By A. Kosiór

Many remnants of gold exploitation in the Middle Ages were found in the Lower Silesia region. The oldest evidence of such activity was found in the neighborhood of Zloty Stok and comes from the 7th century. Mining of precious and non-precious metal ores has a great relevance in the late Middle Ages when advanced metallurgic technologies were mastered, that allowed to obtain gold, silver, lead, copper, zinc and arsenic from complex ores occurring in the oldest middle part of Sudetes. Historically it concerned the area of the Swidnica Principality and Klodzko County. Experience obtained in Freiberg, which is located close to the Lower Silesia, was used in the development of mining. A high level of mining and metallurgic technology was obtained in the 15th century that caused significant increase of production of the metals mentioned above. Unfortunately, the good time of Lower Silesian mining lasted only up to the 18th century; the notion of preservation of cultural heritage was unknown at that time. The Lower Silesian medieval mines were not in such a fortunate situation as the ?Wieliczka? and ?Bochnia? mines, which are operating to present-day, and which made preservation of the most interesting headings and objects possible. All these objects are now available for visitors. However, in the case of the middle Sudetes it seems that it is often sufficient to localize old shafts and headings on the basis of careful observations and old maps and carry out some earthwork to uncover medieval headings and objects of underground mining activity. They are often preserved in amazingly good state; this also pertains to mining devices. Another issue is of course the permanent preservation of that heritage and its possible availability for re-searchers and tourists. Some success has been achieved in that field (Zloty Stok Gold Mine is a good example), but also problems were encountered in many cases. The Lower Silesian Coal Basin, which has not been exploited for 10 years is an evidence that there is not a holistic conception of mining heritage renovation. Many attractive mining objects disappeared irrecoverably from the mountainous landscape of the Middle Sudetes despite common consciousness of their significance for cultural development of Silesia and other regions.

Jan 1, 2006

By Carlos Maurício Fontes Vieira

In the present work a ceramic body, fabricated using a mixture of clays and sand, for roofing tiles, produced in Campos dos Goytacazes, north of the State of Rio de Janeiro in Brazil, was characterized. Characterization was performed by X-ray diffraction, thermo analysis, chemical analysis, particle size distribution determination and plasticity. In addition, technological properties related to water absorption, linear shrinkage and flexural rupture strength were determined in samples fired at 700, 900 and 1100oC. The results showed that the investigated ceramic body has satisfactory plasticity and presents a refractory behavior during firing due to the predominantly kaolinitic nature of the clays.

Jan 1, 2006

By A. F. S. Schoukens

The Mintek Thermal Magnesium Process (MTMP) was successfully demonstrated in November 2004. The pilot plant was operated continuously for 8 days, during which about 30 tons of magnesium producing recipe was smelted in a DC (direct-current) arc furnace at a feed rate of 525 kg/h. The furnace was operated at power levels of 700 to 850 kW, resulting in slag tapping temperatures of 1600 to 1700°C. Magnesium extraction averaged 77 per cent and was as high as 85 per cent during good extraction periods. The furnace generated 70 to 85 kg/h magnesium vapour that was delivered to the condenser where the temperature was controlled at 680 to 720°C. The novel condenser captured the magnesium in a liquid state, which was tapped periodically as required. In total, 15 magnesium-tapping operations were carried out, proving that online magnesium tapping can be consistently performed without any major difficulty. About 3500 kg of crude magnesium was produced with a quality that was similar to, if not better than, that of the Magnetherm?s crude metal. The condensation efficiency averaged 85 per cent, and peaked at 87 per cent, which exceeded the target of 80 per cent set for the pilot scale. A brief magnesium market study was also carried out. Magnesium demand is expected to keep on growing by 6 to 8 percent over the next 10 years and could reach 2 million tons by the year 2020. The growth will be mainly in the die-casting sector for light-weight automotive applications. China is likely to remain the dominant supplier of primary magnesium but competitively priced non-Chinese magnesium producers will be needed to sustain the anticipated growth of 6 to 8 per cent over the next 10 years. In addition, a prefeasibility study was undertaken for a commercial plant. The study confirmed the relatively low capitalcosts of the MTMP process, as well as the competitiveness of theoperating costs, as compared to the industrial electrolytic process.

Jan 1, 2006

By James A. Schneider

The evolution of the American Petroleum Institute (API) design method for axial capacity of driven piles in siliceous sands is explored, and complemented with an overview of how changes in offshore site investigation practice have increased the level of knowledge with respect to vertical variability of soil characteristics. Increased use of the cone penetration test (CPT) provides near continuous profiles of soil type and strength which can be used in calculation methods that address variation in local shaft friction rather than the API method which seems to have initially been based on observations of average shaft friction in relatively uniform sand deposits. Development of a formulation for CPT correlations to axial pile capacity in sand is discussed, along with implications to existing factors of safety used in routine design.

Jan 1, 2006

Laboratory trials were performed in an induction furnace to study droplet formation during lance blowing. Compressed air was blown on a molten iron bath consisting of iron alloyed with carbon and silicon. Steel droplets were collected using a specially designed sampler. The average steel droplet composition and the oxide layer thickness were determined using scanning electron microscopy combined with energy dispersed spectroscopy. In addition, the concentration gradient of elements was determined using a microprobe. It should be noted that a special technique had to be developed in order to prepare the droplet sample. The size distribution and composition of the droplets was also determined using the microprobe. It was found that the carbon content in the droplets was lower than the carbon content in the bulk.

Jan 1, 2006

By D. M. Muir

The mineralogy of residues formed during the pressure acid leaching of arid region nickel laterite ore varies according to the salinity of the process water, alkali cation additives and the overall acid loading. In fresh water, hematite is the main iron-bearing leach residue component, together with amorphous silica and hydronium or sodium alunite/jarosite [(H3O,Na)(Fe,Al)3(SO4)2(OH)6]. As the process water salinity increases, or as NH4+ or K salts are added, alunite/jarosite is the kinetically favoured iron-bearing phase accompanied by an increase in acid consumption. The alunite/jarosite appears as two XRD distinct phases with different Fe:Al molar ratios. In weakly saline water, iron-rich alunite/jarosite slowly transforms to hematite and an aluminium-rich alunite/jarosite together with the release of acid. The addition of potassium salts forms a more stable alunite/jarosite whilst the addition of ammonium salts leads to greater transformation of alunite/jarosite at 250°C. Weakly saline process water gives enhanced nickel recoveries, whilst strongly saline process water gives lower nickel recoveries but higher soluble iron because of chloro-complexation. SEM and microprobe analysis shows very little nickel is associated with the alunite/jarosite and hematite phases. Nickel losses to the residues are attributed to adsorption on amorphous silica and to a lesser extent on alunite/jarosite.

Jan 1, 2006

When overburden depth exceeds economical recovery in openpit coal mines, the use of highwall mining systems has increasingly come into play. However, stability in the highwalls is always a major safety concern during such mining. The U.S. Mine Safety and Health Administration requires that highwall mining operators follow ground control plans that specify the pillar sizes necessary to prevent collapse that would threaten highwall stability.

Jan 1, 2006

At present, discounted cash flow analysis is generally accepted as the preferred method of valuation of mine projects in surface coal mining. One of the major reasons for that is its ability to take into account the time effect of money over the life-of-mine. As a looking-forward method, it requires forecasts be made with regard to economic, technological, technical, geological, and environmental conditions that will prevail in the future. All forecasts are inherently uncertain as they are a function of the uncertainty of all variables of the discounted cash flows analysis. This indicates that the only alternative for modeling the uncertainty in the project evaluation is the development of adequate risk models to serve the decision-making process. The paper offers a model of project cash flows at risk in strip coal mining, which is an integrated corporate risk management solution. The model is based on a stochastic approach that provides the answer to the question about how large is the deviation between stochastic cash flows and the planned value (or that used in the budget) at each time step of the discounted cash flows analysis, that is due to the uncertainty in the model variables. A solution is worked out for the allowable range of the stochastic cash flows variation that determines the probability of achieving the planned value of a mine project. The Monte Carlo simulation technique is used to model the stochastic behavior of the project variables. A case study of an opencast coal mine project is provided to illustrate the applicability of the risk model. The results obtained provide a new understanding of the mine project risk as a component of the project discount rate.

Jan 1, 2006

Gas-liquid contacting in the packed bed is a common operation in metallurgical reactors. Research has shown that, unlike wetting flow, non-wetting liquid flows in the form of discrete droplets or rivulets. Thus, modeling of the liquid phase as a continuum is in contradiction to the observations. Also, for the non-wetting case, continuum models have failed to describe liquid flow path when the liquid source is a point source. The aim of the current work is to put forward a combined Lagrangian-Eulerian approach to model the liquid and gas flow in the packed bed. Liquid is assumed discrete and modeled using a force balance approach. Gas is assumed to be interpenetrating continua and modeled using k-emodel for turbulent flow. Structured packing is assumed and x- ray imaging technique is used to visualize liquid flow lines in the bed. Simulation results for liquid flow path compared with the experiments.

Jan 1, 2006

By C. Taschereau, G. A. Vickell, A. R. Laplante

Evidence in support of an iron-gold corrosion cell during the high-temperature/highpressure elution of loaded carbon is presented herein including, but not limited to, its discovery, mode of genesis, and confirmatory laboratory testwork. A discussion of metallurgical and economic impacts, remedial investigations, plant design considerations, and future work including mitigative possibilities is presented.

Jan 1, 2006

By Brian H. Greene

The U.S. Army Corps of Engineers, Pittsburgh District, is in the final phases of modernizing the locks and dams on the Monongahela River. One facet of this modernization is to replace the existing Locks 4 located on the Monongahela River approximately 40 river miles upstream from Pittsburgh, Pennsylvania. The existing locks consist of a 56-foot x 720-foot main chamber and a riverside 56-foot x 360-foot auxiliary chamber built in the 1930s. Two new lock chambers, each 84-foot wide by 720-foot long, will be constructed at the location of existing Locks 4 and will be named Charleroi Locks. The purpose of the new project is to facilitate navigation on the lower Monongahela River. Pittsburgh is currently the second largest inland waterway port in the nation, and the new locks will be an important component of the navigational infrastructure. The existing lock walls are of mass concrete construction and are founded on wooden timber piles driven to rock through alluvial sands and gravels. The new lock walls were designed to be supported by approximately 300 reinforced concrete drilled shafts, varying in diameter from 4 to 6 feet. To handle axial loads, the drilled shafts were designed for end bearing, with some skin friction. The tips of the shafts will be founded within competent rock. Since the walls will undergo lateral loads, the drilled shaft design also had to consider this loading condition. Some of the drilled shafts will be installed within coffer boxes, which will incorporate a tremie concrete seal down to top of rock. Complicating the design even further was the fact that some portions of the new walls will be supported by shafts that extend some 9 feet above top of rock through alluvial soils, producing a cantilever effect. The first phase of the new lock construction was initiated in the summer of 2005 with a contract awarded to replace the river wall. This required shutting down the existing riverside lock chamber and diverting all river traffic to the longer existing land chamber. The foundation of the new river wall will use 144 drilled shafts. To optimize the design embedment of drilled shafts in rock for the river wall, an exploratory drilling program was conducted by the contractor in July and August, 2005. Based on the quality of the sedimentary bedrock, the shafts will be embedded in rock from 31 to 38 feet. To achieve adequate end bearing resistance, the tips of each shaft will extend through predominantly claystones into a more competent siltstone unit for a minimum embedment of one foot. The contractor also performed an exploratory pile driving program to aid in the construction of the drilled shaft casing and the cut off walls that will encapsulate the river wall. Two demonstration drilled shafts located outside the footprint of the new river wall, will be constructed prior to the drilling of any production shafts. The demonstration drilled shafts will verify that the contractor is able to meet the design criteria and quality requirements of the contract. The river wall contract is currently underway and is scheduled to be completed in 2010.

Jan 1, 2006

By C. Liu

Zeta potentials and settling rates of an oil sands tailings sample taken from Syncrude Canada Ltd's Aurora Stacker Pilot Operation were studied. Two clay minerals, kaolinite and illite, were also studied since these are the major constituent minerals in the fine oil sands tailings. Process water, decanted water as well as distilled water were used. It was observed that the zeta potentials of the tailings solids showed maximum negative values in process water at pH 8-10, which coincides with the pH of commercial hot water bitumen extraction process. The settling rates of the tailings sample were very low, at 0.008 m/hr in decanted water and 0.04 m/hr in process water. The rates were increased to 1.0 m/hr in decanted water and 0.13 m/hr in process water at an addition of 50 g/t Ciba AF1235. Although the settling rate was higher the supernatant was cloudier in decanted water than in process water. Further increase in the dosages of Ciba AF1235 did not increase the settling rates in decanted water but gradually increased it in process water, reaching 0.46 m/hr at 100 g/t. The results indicated that lower concentrations of Ca2+ and Mg2 (in decanted water) benefited settling rates but did not benefit supernatant clarity. Test results also indicated that Ciba AF1235 caused selective flocculation of the tailings sample, since the top sediments had higher illite and lower quartz contents than the bottom sediments.

Jan 1, 2006

By M McLean

This paper deals with change strategies on brownfield and greenfield sites in extractive industries. It draws upon contemporary experiences across Australian, Indonesia and Papua New Guinea (PNG). Change strategies can be used when owners of an extractive industry operation want to optimise their resource. This paper draws upon many tried and proven theories and practices, including the findings of the Tavistock Institute (Trist, Emmery, Bamford, Jaques), as well as the concepts of Adult Learning espoused by Malcolm Knowles and is supported by learnings of Australian based management consultants. This paper reviews a range of approaches that have succeeded in the integration of systems, machines and people, with the key corporate objectives of: increasing productivity; decreasing cost; improving on-time delivery performance and achieving long-term survival. Such integration needs to be measured to show the outcomes from the change strategies and the authors have worked within many measurement regimes and metrics but for the most part, found that JaquesÆ set of metrics being æquality, quantity, resources and timeÆ has gained currency across many Australian operations. This paper contends that investing money in machines alone without a commensurate investment into the people side is counter-productive. Further, if there is not an understanding of processes, ie stable and capable, core and support processes, then all that new technologies will do, is to make what is done badly, only quicker. Recent interventions for the most part, have been cognisant of this balanced approach towards change management. The change strategies described are across extractive industry implementations, using a number of tools and techniques drawn from Continuous Improvement and Six SigmaÖ (registered trade and service mark of Motorola Corporation, USA).

Jan 1, 2006

Outline ? Overview ? Existing Operations ? Mine Planning ? Future Trends ? Market Impacts ? Conclusions

Jan 1, 2006

Pyrometallurgy has played a very important role in southern Africa for at least four centuries. It continues to do so, and recent years have seen many exciting developments in pyrometallurgical technology. The wonderfully diverse rich mineral deposits in this area of the world have provided some unique opportunities for industrial processes to be established. The ?Southern African Pyrometallurgy 2006? conference was set up to showcase southern African pyrometallurgical operations, and to provide a forum for the exchange of ideas between people working at various types of smelters. Papers have been obtained from a wide variety of pyrometallurgical plants in southern Africa. These descriptions of plant operations (as well as some history, and highlights of current work) will provide useful reference information for some time to come. Contributions are also included from universities, research organizations, and engineering companies, so that the full spectrum of pyrometallurgical activities can be covered. The plant descriptions will be published on a website, where they can be updated as and when required, with the eventual goal of having a description of every smelter in the region. The conference venue was selected to be the 'Cradle of Humankind' world heritage area, about 40 km from Johannesburg. Not only does this keep the conference within easy reach of the city and yet far enough out into the countryside to allow people to focus on the conference, it is also within easy reach of many pyrometallurgical plants. There is a particular significance to the choice of location, in that the Swartkrans area close to the Sterkfontein Caves is the site of the earliest evidence of the deliberate controlled use of fire by human beings (about 1.3 million years ago), and this is obviously a necessary precursor to pyrometallurgy. The area also lends itself to a very wide range of outdoor, social, and cultural activities to supplement the technical content of the programme. It is hoped that activities such as a hot air balloon safari and visits to the world-renowned Sterkfontein Caves and Wonder Cave will help to make the conference a memorable one for those able to attend. I trust that the ongoing value of the papers and presentations will make all the hard work of the many contributors most worthwhile.

Jan 1, 2006

By Dan Brown

Deep foundation contracting for transportation projects in the United States has typically followed the design-bid-build model in which contractors bid on a specific work product according to relatively inflexible prescriptive specifications. With continuous flight auger piling and the many types of proprietary drilled displacement auger piling, there appear to be advantages to contracting this work according to a different model. This paper provides a discussion of the use of a performance specification for this work in which the contractor has greater freedom to choose the most appropriate foundation system and also greater responsibility for the performance of the completed foundation. With public agencies subject to open bidding, this type of contractual arrangement presents opportunities to encourage innovation. There are also challenges for implementation in public works projects, notably the selection of qualified contractors and the verification of performance requirements on production foundations.

Jan 1, 2006