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By Alford R. A

The causes of the loss of heavy mineral from mineral sands wet concentrators were identified through detailed surveys of two such concentrators. It was found that tray and spiral sluices preferentially lost elongated panicles, but panicle size had little effect on loss. Recovery was shown to increase with panicle density. The major influences on the recovery efficiency of individual concentrating devices (stans) were feed rate and feed grade, recovery increasing with decreased feed rate and with increased grade. Uneven distribution of total solids and heavy mineral to individual stans contributed to losses through the corresponding effects in feed tonnage and grade. Computer simulation demonstrated that significant recovery improvements could be obtained by appropriate adjustment of splitters to optimise the characteristics of internal plant flows.

Jan 1, 1991

By Neto J. A N

Usually there are organisational interfaces between each stage - companies or departments. Each organisation will have different ideas about "optimum" operation. These ideas will be driven by how the performance of each is measured ' and rewarded. Therefore it is important to set up data acquisition processes with respect to maximisation of overall profitability and resource utilisation. In the simplest case - if the miners are paid on tonnes and the concentrator has severe grade penalties on concentrates, then there is the possibility of a conflict of interest over metal Balance.

Jan 1, 1991

By F. J. Susko

The US Bureau of Mines is using Fourier-transform infrared (FT-IR) analysis to investigate the bonding mechanisrn that occurs during the dewatering of clay slurries. High-molecular-weight polymers are used as flocculating agents in these processes. This investigation presents the results of an FT-!R study of calcium-exchanged montmorillonite treated with polyacrylamide (PAM) and polyethylene oxide (PEO). Both thin film and attenuated total reflectance (ATR) spectroscopic techniques were employed to study this clay polymer system. Results suggest PAM is adsorbed to the clay via the nitrogen atom of the polymer. A waterbridge is involved in the bonding between the clay at d PEO. Evidence also suggests that PEO may be adsorbed directly onto the surface of the clay.

Jan 1, 1991

By C. I. Basilio

The mechanisms involved in the adsorption of modified thiol-type collectors on sulfide minerals have been investigated in the present work. These collectors belong to the broad classes of thionocarbamates, thioureas, thiophosphates and thiophosphinates. They differ significantly from the traditionally used thiol-type collectors, such as xanthates and dithiophosphates, in terms of structural features that involve either the introduction of an additional oxygen donor or the alteration of electron densities on donor atoms. Electrochemical studies suggest that the adsorption of these classes of collectors is probably the result of a coupled reaction of the EC-type, involving an initial electron transfer step (E), followed immediately by a chemical reaction (C). Thus, the overall adsorption process is controlled by both the E, and pK of the system. The role of structural features in changing the interaction of the donor atoms with sulfide minerals is also discussed.

Jan 1, 1991

By Russell J. Foster

Many important materials are derived entirely or partially as byproducts of primary copper, lead, and zinc production. This U.S. Bureau of Mines report examines the collective role of byproducts with regard to the economics of domestic mineral production, and their individual significance in terms of dollar value, end uses, and strategic considerations. The study also analyzes circumstances that have affected the competitiveness and structure of the U.S. copper, lead, and zinc industries, and factors that impact byproduct availability. These factors include production capacity at smelters and refineries, process technology, changing sources and composition of ores, regulations, foreign ownership, and byproduct demand and price. Policy considerations regarding stockpiling, regulations, and research are assessed.

Jan 1, 1991

By Paponetti B. . A.

Gold is usually recovered by cyanidation, thiourea leaching and amalgamation, however the efficiency of these technologies, in the case of refractory ores, is low ever when fuie grinding is practised. For example, .if the gold particles are included in sulphide minerals, the leachant cannot reach them, so they are often lost in the tailings. Hence .it is first necessary to break the sulphide crystals by preliminary treatment such as roasting, nitric .acid oxidation, pressure leaching and bacterial oxidation and then apply a conventional extractive technique for satisfactory gold recovery. This paper describes the effect of biological pre-treatment with Thiobacillus ferrooxidans) on the? extraction ? and? recovery of gold by conventional cyanidate. leaching from; a refractory arsenopyrite ore from Golcuck (Turkey).

Jan 1, 1991

By Evans RH, Todd G

Statistical thinking and statistical process ppq;ro4 are essential adjuncts of total quality management aqd too continuous improvement of operating efficiency arid, p*Nc; a4 W,

Jan 1, 1991

By H. Vedrine

A modelling study has been carried out on the flotation of the Moinho (Portugal) polymetallic sulphide ore, based on pilot plant data. It shows that successfully modelling the flotation of such an ore needs to take into account not only the influence of particle size, but also that of the mineral liberation of the ore. The benefits deriving from the research have been twofold in that the study has: 1. Improved the understanding of (a) the response of the ore to froth flotation and (b) the influence of regrinding the zinc middlings; and 2. Provided models for the optimization of the industrial flotation circuits when the plant starts up in 1991.

Jan 1, 1991

By D. Madsen, B. Salamondra, A. Moss, D. Etienne

"Raise mining at the Namew Lake Nickel Mine in Manitoba uses 3 m diameter bored raises driven at 45 to 50 degrees dip for stope access and drilling. These raises are developed within the orebody on 20 m centres to accommodate electric-hydraulic longhole jumbos and charging wagons. Critical elements of stope development include delineation of are contacts, control of deviation during raise development, optimal stope sequencing to permit a high extraction rate, drill anchorage installation, production drilling and blasting, and ground control. Procedures to deal with these elements are described, with emphasis on the geotechnical investigation for design of open stopes and pillars.Although mining with drilled raises does not have the flexibility to follow large variations in orebody dip, results to date indicate that it can be used successfully in the thicker ore zones. Thinner zones are currently mined using a modified Avoca method. Some flexibility to accommodate variations in orebody dip in thin are zones may be obtained by using alimack raise climbers to drive access raises, and carry longhole drills and charging equipment. Rock quality has been sufficiently good to maintain stable stope walls for full-height mining of primary stapes at 20 m strike length.IntroductionThe Namew nickel deposit is located 60 km south of Flin Flon, Manitoba. It is a moderately dipping (45 to 50 degrees) pipe-like ultramafic intrusion with a sulphide halo enrichment. The diluted recoverable ore reserves at January I, 1990 are 2.2 million tonnes grading 2.05% Ni and 0.7% Cu. The operation is a joint venture between Hudson Bay Mining and Smelting (60%) and Outokornpu Mines Ltd. of Toronto (40%). The mine is budgeted to produce 530 000 tonnes in 1990. The deposit was discovered in 1984 and mine development commenced in 1987.In the raise mining area, primary stopes will be filled with a high quality backfill consisting of cement and quarried limestone. Secondary stopes will be mined out between the primaries in the second pass of mining. The design extraction rate is 94% over all.The orebody above 120 level has an average mining width of 2.4 m, so is too narrow for raise mining. A modified form of Avoca stoping is used."

Jan 1, 1991

By Bruce A. Kuyper

Routine core drilling at the Cove deposit failed to confirm gold-silver grades and length of intercepts observed in reverse circulation drilling. A drilling program was designed to ascertain whether the disparity was due to problems with reverse circulation drilling techniques, core drilling techniques, or the erratic nature of the gold-silver mineralization. Special sampling devices and core drilling methods were employed. Data obtained from core-reverse circulation twins showed that down-hole contamination during reverse circulation drilling accounted for much of the variation between reverse circulation and core drill results. Down-hole contamination occurred as a result of high ground-water inflows eroding friable vein material from hole walls.

Jan 1, 1991

By R. D. Beck

The minerals industry needs the support of al sections of the population if it is going to be able to supply the new materials required for future development. It will achieve this support only if its image is good. Perceived images of the minerals industry are examined in respect of history, technology, environment, safety, education, and economics. Concern is expressed about the low technological image of the industry and the declining number of students enrolling in minerals-related disciplines. It is concluded that it is the professionals, through institutes like The South African Institute of Mining and Metallurgy, who must take the lead in improving the image of the minerals industry. The Presidential Address gives data to support this thesis; data that, is hoped, can be used in efforts to educate people about the minerals industry.

Jan 1, 1991

By R. W. Bartlett

Aeration curing, over- a long duration in wet- red stockpiles, shows promise as an affordable pretreatment method for oxidizing gold encapsulating sulfide minerals, and possibly organic matter, in low grade refractory ores. Following aeration pretreatment, the ore is reclaimed, neutralized, and cyanide leached by conventional practices. Large tonnages of subeconomic material, including mine stripping waste, may he converted into ore by this new technology. The results presented show that a successful application of this technology will likely require crushing to about -2 cm (-3/4 in.), followed by aeration in a wet stockpile for long periods, up m three years. Natural convection may he inadequate, hut forced air ventilation, at modest pressures and power consumption, is affordable.

Jan 1, 1991

By D. J. McKee, D. M. Wiseman

The usefulness of simulation as a technique for metallurgical process design and optimization studies has been greatly extended over the last few years by the development of a number of general purpose simulation packages. The packages, or simulators, all have the common objective of presenting the mathematical models and simulation methods in a form which is readily usable by plant engineers and metallurgists. To date, most simulators have been concerned with steady state simulation, but packages capable of dynamic simulation are now becoming available. The paper outlines the essential features of versatile steady state and dynamic simulators. Typical applications are presented by considering examples of design and optimization studies. Limitation on the use of simulators are also presented.

Jan 1, 1991

By Khamis Y. Haramy

This U.S. Bureau of Mines report describes the use of Bureau-developed flat and cylindrical hydraulic borehole pressure cells. A brief description of the fabrication, installation, and pressurizing equipment is given and pressurizing procedures are discussed. Theories available on evaluation of data from the flat and cylindrical pressure cells and examples of data analysis and stress evaluation are also presented.

Jan 1, 1991

By B. Whitmoyer, J. Tian, J. E. Sneckenberger, M. A. Jerabek, C. A. Chandler

A computational procedure has been developed to determine the lung volume function for the upper airways of the human respiratory system. This analytical procedure computes a person's partial lung volume from an experimental two-microphone acoustic measurement of the upper airway passages obtained through a molded tubular mouthpiece. The theoretical transfer function for the two microphone signals as well as the related acoustic impedance and reflection coefficient for the upper airways are calculated using two-channel spectrum analysis techniques. An inverse spectrum analysis scheme then converts the reflection coefficient to an impulse response from which the airway area function is extracted using an area recovery algorithm. Numerical integration of the upper airway area function yields the lung volume function for the upper airways of the human respiratory sysytem. A software program to accomplish this computation of human upper airway volumes will be described in this paper. Application of this computational procedure to the measured tracheal acoustic impedances of 15 human subjects will illustrate the program's capability toward early detection of lung dysfunction using a prototype clinical facility.

Jan 1, 1991

By Moelle KHR

The successful operation of a longwall face depends significantly on the efficient actions by support systems and on the ability to form a supported beam for a limited time span.The mechanical action of the supports can set up complex stresses in the immediate roofstrata.The cyclic application of supporting loads to the immediate roofstrata of a longwall face creates a special type of fabric disintegration in the rocks -affected. The mode of application and the distribution of the supporting forces is thus severely modified in a number of cases.The occurrence of true fatigue damage in brittle sandstones has been identified by studying the subcritical crack growth and microcrack development in the fracture-tip region. Several mechanical effects peculiar to the cyclic fatigue process have been identified. These effects had not previously been widely recognized. Damage in brittle rocks subjected to cyclic loads is shown to be distinctly different from any other damage processes under either monotonic or sustained (creep) loading conditions. The face support systems will frequently support rockmasses with mechanical properties not identified in conventional monotonic or sustained load tests.

Jan 1, 1991

By Komosa T, Muir D. M

Adequate levels of dissolved oxygen are essential for efficient gold dissolu- tion. The actual levels in plantpuips can be seriously reduced by the presence of oxygen consuming reactive minerals, and reduced oxygen solubility in saline water. The rate of gold dissolution is then limited by oxygen availability rather than cyanide. Ion selective electrode dissolved oxygen meters can give an effective indication of the relative oxygen saturation, but they are not able to give meaningful values of dissolved oxygen in saline water, without custom calibration curves. When the dissolved oxygen concentration is rate limiting, the addition of oxygen or peroxide can improve gold leaching kinetics as well as reduce cyanide consumption.

Jan 1, 1991

By W. Choi

The present study revealed that the bioleachability of a chalcopyrite flotation concentrate is influenced by the semiconductor properties of CuFeS2. The overall reaction of biooxidation,

Jan 1, 1991

By D. Boreck

The Bureau of Mines is conducting research on the feasibility of incorporating in situ stope leaching into active underground metal mines. Stope leaching, a modified in situ leaching technique, proposes to recover metals by leaching fragmented ore in existing underground openings and collecting and processing the metal-bearing solution to recover the valuable metals. If leaching solutions escape from the stope, either through geologic discontinuities or highly permeable zones in the rock, valuable metals dissolved in the solution may be lost. Escaping solutions may also contaminate ground waters. Consequently, in fractured rock, the characteristics of the fractures in the vicinity of the leaching stope must be understood before introducing actual leach solutions into the stope. Effectively characterizing a rock mass requires the integration of several disciplines including structural geology, borehole geophysics, hydrology, geochemistry, and mining engineering. This paper will focus on the general geologic and geophysical techniques that can be used to characterize the rock mass at an underground simulated stope leaching site. The results of several geophysical logging methods, tested at the site, are compared to the geologic core descriptions. Then, the? effectiveness of the different geophysical techniques in delineating fracture zones will be assessed. Knowledge gained through the geologic and geophysical analyses can be used to supplement results from hydrologic testing. This information can also be utilized in designing blast patterns and developing strategies for controlling or blocking movement of escaping leach solutions.

Jan 1, 1991

Selective Flocculation process development generally involves single mineral flocculation tests to identify the appropriate polymer and experimental conditions for achieving the desired selectivity. Invariably the selectivity predicted on the basis of such tests is not realized when mixed mineral tests are conducted. A systematic experimental investigation revealed that adsorption of the polymer on various substrates is critical to selecting the suitable flocculent. Simultaneously, a mathematical model was developed to predict the overall process efficiency with a given polymer. In this paper, results of these efforts to scientifically design a suitable selective flocculation process are presented.

Jan 1, 1991