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By M. Stefanakis, A. Kontopoulpus, K. Adam

The application of Bacterial Oxidation as a pretreatment step for the extraction of gold from the Olympias refractory pyrite concentrate is described. A wide review of Bio-oxidation is presented focusing on the current process developments and commercial applications relevant to the treatment of gold bearing sulphide ores and concentrates. Preliminary batch and semi- continuous tests on the Olympas concentrate indicated that with Bacterial Oxidation quantitative gold liberation may be achieved. fie effect of such parameters as pH, Eh, temperature, particle size, operating pulp density and retention time on the extent of sulphur oxidation and subsequent gold extraction by conventional cyanidation are also examined. Finally, a preliminary evaluation of Bacterial Oxidation as a potential process alternative for the treatment of the Olympias concentrate is presented.

Jan 1, 1989

By E. J. Donovan, O&apos

The use of Dynamic Analysis techniques in the design of conveyor systems is extremely limited. The most frequent use of the technique is in large and expensive systems where the emphasis is on insurance against failure caused by catastrophic tension waves. This paper sets out to illustrate a much wider range of applications where dynamic analysis has been successfully employed. The examples chosen deal with identification and correction of dynamic low tension problems, the variability in take-up movement as other system parameters change, the requirement for proper tuning of starting controls and finally the absolute necessity for a complete understanding of the entire system when specifying brakes for critical applications. The intent of the paper is to get designers to view a conveyor as a system of interacting flexible components rather than as a single rigid body.

Jan 1, 1993

By John P. Dunford, Lewis A. Martin

Researchers from the Spokane Research Laboratory, National Institute for Occupational Safety and Health, in cooperation with engineers from the Department of Mining and Geological Engineering, Montana Tech, Butte, MT, conducted tests to evaluate the tensile strength, fiber count, and adhesion of shotcrete applied to panels at the Chief Joseph Mine, a research and training facility operated by Montana Tech. The tests were conducted in the mine ramp 45 m (150 ft) inward from the access portal at a 15.25-m- (50-ft) long test area divided into five 3-m- (10-ft) long sections. The shotcrete was applied with an Aliva 240.5 machine fitted with a predampener. Different amounts of fiber were entrained for each panel. Background data for the tests were obtained from earlier tests in Nevada, where the typical amount of fiber in the shotcrete is 6.54 kg/m3 (11 lb/yd3). All shotcrete was applied to a minimum thickness of 76 mm (3 in). Cylindrical cores were drilled at the wall-rock interface, and adhesion was tested after 28 days of curing. The goal of this research is to reduce the need to install multiple supports at the advancing face by creating a safer mining system that limits the time miners are exposed to unprotected roof.

Jan 1, 2005

By S. Kelebek, S. O. Fekete

The flotation process developed at Falconbridge laboratories utilizes sulphur dioxide and diethylenetriamine (DETA) reagent combination in the depression of pyrrhotite to allow its separation from pentlandite and chalcopyrite. DETA by itself has failed to produce flotation selectivity with samples from plant and pilot plant streams which showed relatively high redox potentials. However, DETA was found to function effectively on laboratory-generated samples under certain conditions. The results of poor depression are in keeping with thermodynamic calculations which indicate that in the presence of sufficient xanthate and DETA, the formation of ferric dihydroxy xanthate and dixanthogen is possible under oxidizing conditions. The use of sulphur dioxide alone has also resulted in a rather poor depression of pyrrhotite. However, the combined use of these reagents has resulted in an efficient and consistent separation of pyrhotite from pentlandite and chalcopyrite. Various aspects of this selective flotation system are presented along with a discussion on possible operating mechanisms.

Jan 1, 1995

By W. Blake, J. Mahaut, W. Hustrulid

Division II at Kamoto mine in Kolwezi, Zaire represents a transition zone between Divisions I and III where transverse and longitudinal cut-and-fill rooms were being mined. Because this transition zone had been geologically depicted as being badly faulted the mining in this division had been deferred to a future time. However, to increase production and to reduce mining costs by carrying out the mining of the 3 divisions simultaneously, it was decided to mine Division II. The mining research group of Gecamines was given the task of designing a mining geometry then testing this design in a full scale test. Based on an evaluation of the faulting and fracturing of the 2 parallel orebodies and on an extensive in situ testing program preliminary mathematical analyses were used to develop and evaluate room and pillar designs in the 35°-65° dipping bedded formations. Based on these analyses and the constraints of having to fit the design of Division II to grade into Divisions I and III in a logical manner, a mining geometry for Division II evolved. To test this design an instrumented room was excavated in the most critical area. The results of this full scale testing showed that the behavior of the roof and wall rocks were as had been predicted by finite element computer model studies which incorporated the material properties and results of the field testing. The room geometry design was both judged and observed to be stable, hence mining commenced.

Jan 1, 1977

By G. Yang, M. J. McPherson, P. Mousset-Jones, G. Danko, F. Calizaya

In the last 20 years, studies on controlled flow recirculation in various countries have been carried out in both coal and metal mines. These studies have shown that in addition to economic gains, partial flow recirculation can be used to provide mine workings distant from surface access points with the required volumes of air. These studies have also shown that the operation of fans and regulators, used in a recirculation system, will induce transients in gas flow and gas concentration. Various models have been developed to explain the problem. However, most have failed to incorporate important factors such as diffusion and dispersion in the modeling process. This study examines the theoretical background of gas emission transients from caved areas in coal mines, represents the problem by a "tank-airway" network model, and provides a possible solution. The study also presents the results gained from a laboratory model constructed to evaluate the major factors affecting the shape and duration of gas flow and gas concentration transients in an airflow recirculation system. In this model, the gas injection system was rearranged to simulate the variations in gas emission rates due to changes in air pressure. Within this model, a set of booster fans and regulators were used to generate the changes in air pressure within the model. Finally, the study presents an algorithm and a computer program GASTRAN, developed to analyze the gas concentration transients and calculate the pollutant transport levels in a complex ventilation network. The application of the program is illustrated by means of an example problem.

Jan 1, 1991

By Christopher J. Hall

It has been known for a long time that summing pressure drops and rises due to friction, shock, fans and natural ventilation is incorrect. In fact, lost works and works should be summed. In spite of this, the traditional method of finding a fan/system operating position has been the H/Q Curve. This paper presents (lost) work/m curves, progressing from a single fan moved around the system to include natural ventilation work, and fans in a series, parallel and series/parallel. The solutions obtained graphically are substantiated by dry air thermodynamic solutions, and the traditional solutions are shown to be in error. This method of solving problems is particularly useful when moving fans around the system, and essential in series/parallel and series situations with substantially different fan densities. The dry air analysis is employed because of its simplicity. Real air, with evaporation and condensation, will react somewhat differently, and one should use real densities (i.e.[l + w +w]/va ) when using this method. One source of error when applying this method to real air, although probably not major, will be investigated in a subsequent paper. Friction and shock losses are proportional to the square of the mass rate of flow, leading to the typical parabolic system curve. However, the unbalanced water stuff potential energy term, on a unit mass basis, is substantially independent of the mass rate of flow. It is possible that this could be handled as a negative natural ventilation work.

Jan 1, 1987

By G. Fehr, B. B. Panda, R. Bansberg, K. Arnold, T. Freiman

To evaluate the potential for process solutions to contaminate groundwater outside of the area of the Oxide Pit, it is necessary to predict the ultimate maximum pit lake elevation once pit-related mining activities have ceased. A water balance model was developed based on the existing pit geometry, the groundwater flow equation, and assumed hydrologic input parameters. The model assumed that at any point in time, total inflow into the system (i.e., direct precipitation, surface water and groundwater) minus outflow from the system (evaporation from the lake surface) was equal to the change in the pit water volume. The pit lake depth over time was predicted by assuming a succession of steady- state water balance conditions over short time increments. An analytical method using a spreadsheet and computer model was employed in this study to model the filling of the lake in the Oxide Pit. A sensitivity analysis was performed to evaluate uncertainty associated with the input parameters in the model. The sensitivity analysis indicated that the model was most sensitive to values of precipitation and evaporation and to the static water table.

Jan 1, 2003

By J de Cuyper, G. Rinelli, A. M. Marabini, V. Alesse, W. Freyberger

Salicylaldehyde, a chelating agent for tin, has been found to function as a collector for the flotation of cassiterite. Infrared and nuclear magnetic resonance studies clearly show that salicylaldehyde can form a chelate compound in bulk and at the surface. Results are also given for the flotation of a tin ore with this reagent.

Jan 1, 1976

By Alejandro Sanz, Juan Luis Magro, David Mazeyrie

The Hampton Roads Bridge-Tunnel Expansion Project (HRBT), initiated by the Virginia Department of Transportation (VDOT), will add two new 1.5-mile TBM bored tunnels to the two existing immersed-tube tunnels between artificial islands, part of the connection between Norfolk and Hampton under the Hampton Roads Harbor in Virginia, USA. The new bored tunnels will be built by Hampton Roads Connector Partners (HRCP), a joint venture of Dragados USA, Vinci Construction, Flatiron Constructors and Dodin Campenon Bernard. This paper covers technical discussions that led HRCP to select a Variable Density TBM to address the challenges of this tunnel project, including but not limited to (i) the diameter of the bore: a 46 feet (14.04 m) diameter machine that constitutes the second-largest TBM ever used in the United States; (ii) shallow ground-cover under the water table; (iii) challenging and varying geology along the alignment, with mixed-face conditions and different types of ground modification zones; and (iv) the high TBM operating pressures required—all these and other challenges in a sensitive marine environment.

Jun 13, 2021

By S. G. Hardcastle, Akbar Sheikh

In Canadian underground uranium mines, bacterial leaching is being increasingly applied to low-grade ore reserves. At Denison Mines Limited uranium operations, old stopes are used as leaching vessels; these contain a leaching muck pile brought down by drilling and blasting from the back which contained a low-grade reef. The bacteria used require atmospheric oxygen to oxidize the pyritic ore. A study was initiated to evaluate the ventilation, including oxygen supply, specifically, of flood leaching stopes during their rest period. The method of ventilation investigated was a single ended compressed air system which feeds airlines laid under the muckpile and carried through the inlet pressure bulkhead. The air delivery system was tested for post- blast integrity with a sulphur hexafluoride, SF6, tracer gas technique. This was injected into the intake compressed air line and collected at the stope's borehole exhaust in grab-sampling bags. The samples were analyzed with a laboratory gas chromatograph and results provided information on the stope's airflow, average residence time, overall clearance time, volume of the airpath and the airflow distribution. The borehole exhaust was monitored by anemometer and psychrometer and indicated that the psychrometric conditions in the stope were independent of the area's ambient climate. Evaluation of the exhaust's standard gaseous composition showed the oxygen consumption of the bacteria to be independent of the investigated flow range. Field derived results are compared with computer models, theoretical predictions and laboratory investigations.

Jan 1, 1987

By Richard A. Bideaux

In mid-1975, the United States Borax & Chemical Corp., a member of the RTZ group, engaged Computing Associates, Inc. (CAI) in a continuing project to model their operating property at Boron, CA, with the goal of computerized assistance in medium- and long-range open-pit mine planning. Their property, 161 km (100 miles) northeast of Los Angeles, is the largest producer of borate minerals in the world. Because of unusual geological complexity, this unique deposit presents interesting problems in computer modeling, compared with the coal, uranium, and other metallic deposits with which CAI ordinary deals. Mine planning for Boron has historically been based on manually plotted contour plan maps and cross sections, with geological reserves derived from manual triangularization of the drilling pattern. Standardization and reproducibility of log interpretation, contouring, and reserve calculation were principal goals of using the computer. Additionally, it was desired to shorten both the time and cost of a planning cycle, while at least equalling the accuracy of the manual planning. The present recovery plant processes only water-soluble borates; at some time in the future it will be necessary to recover acid-soluble borate minerals as well. With computer assistance the economics of this changeover point can be more thoroughly evaluated.

Jan 1, 1979

By L. Gertsch, R. Gertsch

Mechanical mining is steadily gaining in usage in the mining industry. A variety of machines are now being used, including tunnel boring machines, roadheaders, continuous miners, surface miners and augers. These machines have advantages compared to drill-and-blast mining methods, including increased safety, lower cost, uniform muck size and accurately sized openings. A century of experience with mechanical methods has paid dividends to the coal industry. Current trends guarantee eventual development of true general-purpose hard-rock mechanical mining machines. When several significant challenges have been met, mechanical miners will become integrated mining systems and will determine the design of mines.

Jan 1, 2002

By C. E. Tackett

The Greenwich Collieries Co. is a subsidiary of the Pennsylvania Mines Corporation, and a wholly owned subsidiary of the PP&L Co. which serves the northeastern portion of Pa. PP&L annually consumes about 11 million tons of coal per year and is the largest consumer of both bituminous and anthracite coal on the eastern seaboard. Development work for Greenwich started in 1969. The coarse coal plant was constructed in 1970, with the raw fines bypassed. This worked very well for our requirements at that time; however, the Greenwich mining plans were extensively changed, longwall mining units were installed and low coal was encountered, resulting in dirtier coal, a finer coal and an ever increasing ash in the shipped product. All this demanded a more efficient ash removal process for the fine coal fraction. In 1971, the Pennsylvania Department of Environmental Resources and the Federal Environmental Protection Agency were pushing for the now stringent sulphur emission limits at our power plants. The Greenwich Mine coal reserves contained large quantities of 3.5 to 4% sulphur along with some low sulphur reserves. It was, therefore, essential that any new plant have the capability of efficient sulphur removal to meet the Pennsylvania Department of Environmental Resources and the Federal Environmental Protection Agency required limits. To meet these limits our design would have to be capable of producing a product of 2.0% sulphur or less.

Jan 1, 1977

By G. R. Brunskill

The molybdenite flotation plant at the Magma Copper Co. San Manuel concentrator has been in operation since 1956. In January of 1980, the plant was converted from a hydrogen peroxide-ferrocyanide process to the current sodium cyanide-sodium hydro- sulfide process. This paper is an operational review of Magma Copper Co.'s molybdenite recovery circuit, column cell flotation experience, and use of on-stream X-ray fluorescence analysis.

Jan 1, 1987

By James L. Vanderbeek

The Chino concentrator commenced operation in 1982 as a SAG-ball mill circuit which could process 37,500 stpd of ore. Since 1982, a series of process improvements such as the addition of two stages of SAG recycle crushing, allowed throughputs to increase to more than 48,000 stpd, at the expense of significantly coarser flotation feed sizing and reduced recovery. To compensate a third (tertiary) stage of grinding consisting of four 1250 hp Vertimills was installed which has allowed the flotation feed size and recovery to return to historical levels. The design and operational characteristics of the Tertiary Grinding Circuit are described.

Jan 1, 1998

By M. Ghiani, R. Ciccu

After a short review of the basic concepts underlying the application of selective flotation and electrostatic separation to the beneficiation of phosphate ores, the paper deals with the results obtained with these two technologies for a number of run-of-mine ores of different origin and distinct mineropetrographic features. Problems are discussed in the light of the minero-petrographic characteristics of the ores.

Jan 1, 1993

By J. A. Pagliero, R. T. Quiroz, S. H. Castro

Selected voltammograms in tetraborate buffer solutions in the presence of ethyl xanthate or isopropyl xanthate at pH 9.3, for chalcocite, covellite, chalcopyrite, and enargite mineral electrodes, are presented. The concept of critical Eh of dixanthogen condensation (Ehc) is introduced, and the line of Ehc is thermodynamically defined in plots of log [X i] vs Eh, for methyl, ethyl, propyl, and butyl xanthates. A reaction scheme of xanthate oxidation in four steps, involving the dixanthogen condensation step, is proposed. A first attempt to interpret mineral flotation from a more general point of view is made. The electrochemical mechanism of dixanthogen formation and condensation is considered as a particular case of a more general and relevant phenomenon, which is the decomposition of the collector giving hydrophobic colloidal forms, whose associative behavior in bulk solution and at the mineral/solution interface is governed by colloid chemistry.

Jan 1, 1989

By R. R. Jozefowicz, T. X. Ren, J. S. Edwards

The control of methane emission into underground mine workings is important both for the safety and productivity of the mine. As deeper and gasser coal seams are mined, ventilation methods involving increasing air pressures and quantities across mine workings may not be able to cope consistently with methane emission rates during the production cycle. An accurate prediction of methane emission into mine workings is of great significance in the design of ventilation systems and additional methane control methods if required. Research has been conducted to develop a numerical method for simulating methane flow through strata in which permeability is strongly influenced by mining-induced stress. To achieve this objective, both numerical modelling using Computational Fluid Dynamics (CFD) and laboratory tests on rock samples and granular materials under triaxial stress condition were carried out. Correlation has been established between stress and permeability characteristics of rock-measure rocks and laboratory results are being incorporated into the CFD models. This paper introduces the use of CFD techniques to model methane flow through permeable strata around longwall coal faces currently undertaken at the University of Nottingham.

Jan 1, 1997

By M. Kumral

The in-situ mineral characteristics of a deposit are simulated by sequential co-simulation and averaging the simulated characteristics within specified block volumes creates a three-dimensional block model. This model is then submitted to optimal open pit and production scheduling algorithms. As the market values of industrial minerals depend on the satisfaction of predetermined blending criteria rather than metal content, a Linear Programming (LP) scheme has been used to identify all blocks that can be included in the blend without violating the grade requirements. The Lerchs-Grosmann algorithm using the blocks identified by the LP program determines optimal pit limits. All blocks that lie outside the optimal pit are removed from the system and the blocks within the optimal pit are submitted to the production-scheduling algorithm. Production scheduling optimisation is done in two stages: Lagrangean parameterisation, resulting in an initial sub-optimal solution, and multi-objective simulated annealing (MOSA) improving the sub-optimal schedule further.

Jan 1, 2002