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By Sadan Kelebek, Gerhard W. Heinrich, Peter F. Wells, Peter J. Whittaker

"Based on plant mineralogical data & circuit modelling, a pilot plant campaign was conducted at Strathcona Mill to identify options for improving the performance and operating flexibility of the copper-nickel separation circuits. Emphasis was given to options for combined treatment of the two feed streams (primary nickel ore rougher concentrate and copper ore circuit concentrate) to obtain more flexibility in the use of existing column flotation capacities. The pilot test results demonstrated that circuits which incorporated preconcentration prior to column flotation gave the best metallurgical results. Maximum column carrying rates were also related to the preconcentration. Predictions that increased circulating loads from the column scavengers would improve copper-nickel separation performance were confirmed.IntroductionThe copper-nickel separation circuits at Falconbridge's Strathcona Mill produce a high grade (>30% Cu) copper concentrate most of which is treated at the Falconbridge Kidd Creek smelter near Timmins. The remaining nickel concentrate which still contains approximately 20% of the feed copper is combined with other lower grade nickel/copper concentrates and shipped to the Falconbridge nickel smelter. The separation is required because of the limited capacity for copper processing in and downstream from the nickel smelter. Since no nickel is recovered at present in the Kidd smelter, the challenge is to minimize the nickel content of the copper concentrate.At present there are two independent separation circuits treating the rougher concentrates from the copper and nickel circuits as shown in Figure I. The minerals treated are mainly chalcopyrite and pentlandite but there is up to 25% of the copper present as cubanite in the copper ore. The circuits were kept separate because the flotation rates and froth characteristics were very different, probably because of the presence of cubanite and the large difference in the concentrate grades feeding the circuits."

Jan 1, 1995

By C. L. Schneider, R. P. King

Size distributions and liberation spectra were measured in samples taken from 10 streams in a taconite milling circuit under normal operating conditions. The size distributions were deter- mined by sieving and the liberation spectra by image analysis using the linear-intercept method with proper stereological correction. The measured data were used to validate a simulation of the milling circuit using MODSIM which included the calculation of both size distributions and liberation spectra. Both the measured data and the simulator showed that liberated magnetite was returned to the mill in the cyclone underflow. The simulation will be used to improve the economic performance of the plant.

Jan 1, 1995

By Changwoo Lee

Under drastically deteriorated situations, diesel equipment was introduced to some of local coal mines, aiming at higher productivity and better safety. To accommodate various diesel equipment in conventionally developed mines, mining system itself had to be modified; much larger trackless haulage ways were excavated. Possible health hazards of diesel not taken into account at the beginning become a serious concern and effective control measures are being searched for. The purpose of this paper is to study the diffusion characteristics of diesel exhaust in local coal mines. One of the parameters affecting dispersion of diesel contaminants is the coefficient of turbulent diffusion. Since CO2 is known to be closely correlated with other contaminants such as CO, NO, NQ, SO2 and RCD, it was chosen as a tracer gas in a series of dispersion experiments. A large diesel passage as well as a conventional track haulage way were the sites for the experiments. Rectangular dispersion pulses were generated for 30 ~60 seconds and CO2 concentrations were recorded at several locations 50~190 m downwind. The diffusion coefficients calculated graphically vary between 0.10~0.48 m2/s at both haulage ways. The results are analyzed to find any correlation with the air velocity and the distance from the disperser. Skobunov's empirical formula is applied to the experimental data for comparison and the relationship between Reynolds number and Ex/Dp/sci0.4 Sc1…

Jan 1, 1995

By J. L. Watson

n the U.S., lead has been produced via blast furnace processing for over a century, and the slags from that pyro-metallurgical process have been accumulating on industrial sites over that extended period. Lead blast furnace slags typically contain both lead and zinc compounds in an iron-silicate matrix, and it appears highly likely that such materials will have to be processed in the near future to meet with EPA regulations. Thus it is appropriate to investigate possible processing routes to render the slags non-hazardous and simultaneously to recover metal values to partially off-set the inherent high cost of processing such materials. There are two major processing alternatives: one being pyrometallurgical and the other hydrometallurgical. The research reported here investigates leaching/solution purification/recovery processes for lead and presents experimental data for the treatment of lead blast furnace slags from S.E. Missouri. The results of the research suggest that both lead and zinc can be removed effectively from the slag, and that metallic lead can be recovered directly from the organic extractant utilized for solution purification.

Jan 1, 1995

The current understanding of the mechanics of rock fracturing during smooth blasting is largely empirical and qualitative due to an inability to model the dynamic process at the fundamental level. In order to overcome this difficulty, a numerical simulation of smooth blasting is performed using the Dynamic Lattice Network Model. This model is capable of simulating material inhomogeneities and the dynamic evolution of fragmentation at the micromechanical level. In this study, smooth blasting techniques are numerically analyzed to characterize the development of the damage rock zone during explosive fracturing.

Jan 1, 1995

By Fuller T

This paper introduces the technology used in laser surveying systems, and the development of a reflectorless one-man total station. These systems are being used for applications such as blast pattern surveys, face profiling, muckpile surveys and the general survey of inaccessible areas. Black Diamond Solutions is continuing to assess new technology and develop integrated systems for applications in the mining industry.

Jan 1, 1995

By J. R. Koehler

Effective barrier pillar design is essential for safe and productive underground coal mining. This U.S. Bureau of Mines report presents an overview of available barrier pillar design methodologies that incorporate sound engineering principles while remaining practical for everyday usage. Nomographs and examples are presented to assist in the determination of proper barrier pillar sizing. Additionally, performance evaluation techniques and criteria are included to assist in determining the effectiveness of selected barrier pillar configurations.

Jan 1, 1995

"Line Creek Resources Ltd. produces three million clean tonnes per year of metallurgical and thermal coals for the international market. The mining operation, which is located in the mountains of southeastern British Columbia, produces coal from four pits by conventional truck and shovel methods.The South Pit, which has been in operation since J982, has a benched highwall 490 m in height. Shallow dipping coal seams at the base of the syncline formation will be exposed in the highwall over the next four years of pit life. The first of these seams, which will measure 500 m in final highwall length, was exposed in J994. An auger, powered by a 1250 hp engine capable of cutting 2.2 m diameter holes, was brought on site in J994 and has proven to be a successful means of recovering coal from the J3 m thick seam.This paper covers the background to the selection of an auger mining method to recover highwall reserves together with the geotechnical and methane considerations for this approach.IntroductionLine Creek Resources Ltd., a wholly owned subsidiary of Manalta Coal Ltd., owns and operates the Line Creek mine. The operation which consists of four active pits, a processing plant, and rail loadout is located in the southeastern coal fields of British Columbia. Figure 1 shows the general area.The coal bearing sequence at the mine is preserved on the east and west limbs of a major syncline. Up to twelve mineable coal seams, ranging in thickness from 2 m to 15 m are contained in the formation. Within the pits the seams are stratigraphically consistent and structurally undisturbed, except for small-scale thrust faults that create multiple repeats of the seams."

Jan 1, 1995

By Richard D. Hagni

Reflected light microscopy is routinely applied to the study of ore minerals and textures in polished sections prepared from a wide variety of ore specimens. With the increasing interest in environmental problems, the important role of the reflected light microscope in the precise phase identifications and the determination of the textural relationships between those phases needs to be recognized. Among other environmental applications, the microscope has been applied to the recognition of lead smelter particles from remote collect sites in Missouri and those particles have been compared to dust particles from specific localities at the nearby lead sinter plant and lead blast furnace. Dust from a secondary copper refinery has been studied for its mineralogy. Soils in the vicinity of a Missouri lead smelter have been studied for their mineralogy in preparation to the clean up of those soils. Electric arc furnace (EAF) dusts, recently classified as hazardous waste by the EPA, have been examined for their mineralogy and textural intergrowth in order to better evaluate proposed metallurgical treatment procedures to render the dust non-hazardous. The initial products from experimental metallurgical treatment of EAF dusts also have been studied to aid in determining the effectiveness of those treatment procedures. Refractory gold sulfides that have been roasted in the presence of lime to retain environmental objectionable sulfur and arsenic while recovering the gold have been studied by RLM to determine their mineralogy, porosity, and permeability for cyanide leach solutions. These case histories illustrate the applicability of ore microscopy to the study of problems related to environmental concerns.

Jan 1, 1995

By M Ash, P Bellairs

The world class iron ore mines at Mt Whaleback, Tom Price and Paraburdoo located in the Hamersley Province of Western Australia must mine the Mt McRae Shale to obtain high grade ore from the Dales Gorge Member of the Brockman Iron Formation. The Mt McRae Shale contains a Black Pyritic Shale lithology that reacts with Ammonium Nitrate based explosives. This paper provides an overview of the problems associated with mining this reactive rock type as well as the development of a comprehensive procedure to safely and efficiently blast, excavate and dispose of this material.

Jan 1, 1995

By A. Fyson, M. P. Smith, Margarete Kalin

"Drums containing 0.07 m3 of pyritic waste rock from a zinc/copper mine, with and without Natural Phosphate Rock (NPR) additions (40 kg/t waste rock) were set up outdoors. The effluent chemistry has been monitored over a period of 709 days. In the presence of NPR, the cumulative acidity discharged from 7 out of 8 drums was 80 % less than that discharged from drums without NPR. Mixing NPR throughout the drums was more effective in reducing acidity than placement of the NPR in a layer in the drum. NPR treatment was more effective for 'fresh' waste rock than for material which had weathered for more than 4 years. It is concluded that application of NPR to pyritic waste rock could greatly reduce acidity generated.IntroductionWaste rock dumps are significant sources of acid, generated by the oxidation of sulphides. Oxygen and water supply are oxidation rate-controlling factors, and oxygen supply is the reaction-limiting component. If secondary minerals can be formed on the surface of the rocks, pyrite oxidation and therefore acid generation may be reduced or inhibited. Neutralizing agents such as limestone do not prevent the oxidation of pyrite but treat the resultant acid mine drainage (AMD) or acid rock drainage (ARD).Meek et al. (1991) determined in pilot scale experiments that apatite mixed with tailings was more cost effective than liming or use of PVC liners to reduce oxygen and water penetration into the tailings. Phosphate is not acting as a neutralising agent but it creates a chemical condition on pyritic surfaces which prevents reactions of the oxidising agents. Precipitation of principally iron phosphates physically isolates the pyrite surfaces from further oxidation (Ziemkiewicz 1990; Evangelou 1994). The chemistry of the phosphate effects has been described by Spotts and Dollhopf (1990). Secondary mineral formation was evident in the leach pile at Gibraltar when leaching was impaired (Scott, 1991) indicating a link between oxidation and the mineral-formation process. This paper reports on effluent characteristics when waste rock is generating acid in the presence of NPR."

Jan 1, 1995

By H. B. Miller

By its nature, underground metal mining is unlike any other business in the industrial sector. Operations are continuously exposed to economic risk as a normal consequence of mining due to uncertainties associated with the? deposit, excavation, and ever changing political, regulatory, and market conditions. Out pacing advances in productivity and technology, these conditions have contributed to the steady decline of underground hardrock mining in the United States. This paper investigates the trends and major factors believed to be responsible for this decline. Special consideration is given to changes in direct operating costs, labor productivity, and production capacity.

Jan 1, 1995

By John C. Heter

The P.W. Gillibrand Company holds 705 placer and lode claims in the Precambrian San Gabriel Anorthosite Complex of the western San Gabriel Mountains. These claims contain large tonnages of ilmenite, magnetite and apatite with anomalous quantities of zirconium (zircon), niobium, vanadium and rare earth elements. Stockpiling of heavy mineral concentrates associated with aggregate mining from alluvial pits has occurred since 1984. The limited reserves of material from these alluvial deposits and their relatively low heavy mineral grades caused Gillibrand Company to initiate an extensive drilling and exploration program to develop the hardrock resources of ilmenite, apatite and magnetite.

Jan 1, 1995

Anomalous geologic or stress conditions ahead of the longwall face can cause great harm to both the individual miner and the mining operation as a whole. The U.S. Bureau of Mines has been developing seismic tomography techniques to image the panel ahead of the face. This paper presents the results of a field effort in which a 60-m (200-ft) segment of a longwall panel containing a fault zone was surveyed daily as the face approached. Stress distribution, geologic structure, and dynamic elastic properties within the panel were plotted and compared to static laboratory measurements. The surveys successfully imaged an anomalous stress concentration, likely influenced by the presence of the fault zone. The calculated dynamic physical properties generally agreed with laboratory measurements.

Jan 1, 1995

By M. J. Gouws, T. P. Knoetze

The spontaneous combustion of coal and the explosion of coal dust are two phenomena that were identified by the South African mining industry as requiring investigation. Research contracts were awarded to the G.P. Badenhorst Research Facility of the CSIR and the Department of Mining Engineering of the university of the Witwatersrand by the now defunct National Energy Council. Both projects entailed tests on numerous coal samples in specially designed apparatus. Since the completion of the project, attempts have been made to predict experimental results without incurring the cost of performing experiments. This paper describes predictive indices, based on routine laboratory tests, that were developed by the different research teams for their particular projects. A comparison of the results obtained by applying the spontaneous combustion liability index and the explosibility index to common coal samples indicates that, in general, propensity to spontaneous combustion and explosibility exhibit an inverse relationship. A brief overview is given of some major South African coal-mine disasters.

Jan 1, 1995

By C. H. Sampaio

The effectiveness of modem spirals in the processing of fines from Brazilian coals is assessed and discussed. Coals representing the four major coalfields in Brazil have been cleaned in Reichert LD 9 spirals in pilot and industrial plants and performance results are here presented. Normalized distribution curves for all equipment and splitters are presented and were modeled using an empirical model. These data have been compared with those for shaking tables and water-only cyclones (WOC), and it has been observed that, in the size interval investigated, spirals have indeed superior accuracy than WOC and comparative performance to tables. By analyzing experimental as well as simulation results it could be observed that although limited by the poor liberation characteristics of most Brazilian coals, significant ash and sulfur removal could be achieved using spirals.

Jan 1, 1995

By Gang L

Seventy-nine gold deposits and prospects have been discoveried in the Jiamusi region of northeast China, and constitute one of the most important gold metallogenic belts in China. All these endogenic gold occurrences can be subdivided into three main deposit types: (1) porphyry related; (2) metamorphic-intrusive hosted, and (3) sediment-hosted deposit. The first two types of gold deposit are spatially and temporally related to Mesozoic Yanshanian granitoid intrusions with hydrothermal activity channelled along crustal-scale fissures. The ultimate cause of the Yanshanian magmatism is considered to be the subduction of Pacific oceanic lithosphere beneath the Eurasian continent. In contrast, The chemical sediment-hosted deposit is typified by the Dongfengshan gold deposit, and genetically related to Proterozoic sedimentation and Mesozoic igneous activities.

Jan 1, 1995

A major factor in the economic development of New South Wales has been the ready availability of coal for the major industrial and urban centres of Sydney, Newcastle and Wollongong. Historically, the presence of high quality coal near these areas has acted as a catalyst to urban and industrial growth. This easy access to low cost coal resources over the past 200 years has given rise to a commonly held belief that New South Wales contains vast coal resources sufficient to meet any foreseeable demand. However, a recent study undertaken by the Coal Resources Development Committee has found that New South Wales is likely to face a serious shortage of economically mineable coal in the future. Forecasts predict that demand for New South Wales coal will increase by about 40 per cent, and then remain at about that level for at least a further ten years. To meet such demands, the coal industry will require access to economic high quality coal resources.

Jan 1, 1995

By D. S. Kostick

Soda ash production in the United States during 1994 increased 4%, reaching 9.3 Mt (10.2 million st). That was the second highest production year. Domestic nameplate soda ash capacity is about 11 Mt (12 million st). Overall, the industry operated at about 85% of capacity. Some companies produced at 100% of capacity while others produced at below their design ratings. Although domestic soda ash consumption was slow during the first half of the year, third- and fourth-quarter sales increased, especially in the flat¬glass and fiberglass sectors. These two sectors increased because of greater demand for glass products in the automotive and construction industries. Soda ash sold for pulp caustic soda increased during 1994. This was due to higher prices for and reduced availability of electrolytic caustic soda. It is often preferred for pulp digestion because of its stronger alkalinity.

Jan 1, 1995

By Duniam P

Sequencing of large underground firings is a critical aspect of blast performance. Using theory developed in open cut operations, where blast results are easier to quantify, a new technique for sequencing underground mass blasts has been developed. The basis for the technique is to identify timing regimes to control fragmentation and relief then apply non-electrics to fit these criteria. The use of computer software to graphically interpret delay statistics enables the evaluation of designs in a realistic manner.

Jan 1, 1995