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By H. Y. Sohn, H. K. Lin

The leaching of primary porphyry chalcopyrite ore under simulated solution-mining conditions was studied using a packed-bed reactor. A mathematical model incorporating the intrinsic leaching kinetics of chalcopyrite and pyrite grains, the pore diffusion of dissolved oxygen within the ore fragments, liquid-solid mass transfer, and the effect of fluid flow and axial dispersion was formulated and tested for the overall leaching process. The dependence of oxygen solubility on ionic strength of the solution was also incorporated into the model. Satisfactory agreement between model pre- dictions and experimental data was obtained. The model can also predict the rate of the leaching process under different temperatures, oxygen pressures, solution flow rates, and different size distributions of ores.

Jan 1, 1991

By Hardy J. Smith

The rock mass parameters which need be evaluated to estimate the rippability of rock are briefly outlined and their significance is discussed. Several methods used for estimating rippability are compared, and the advantages of taking into account a wide spectrum of rock mass parameters are emphasized. A systematic means of numerically weighing six rock mass parameters to produce a Rippability Rating (RR) is recommended, and a method of correlating this rating with the refraction seismograph method and with tractor horsepower is shown. Although the overall method demonstrated is systematic and yields specific numerical results, an integrated approach is recommended to its application, taking into account: the Rippability Rating; seismic velocity and geologic material; and other engineering judgment factors.

Jan 1, 1986

By I. Iwasaki, K. A. Smith, X. Cheng

A cathodic decomposition model was examined for both pyrrhotite and chalcopyrite in an attempt to analyze the formation of surface coatings in deoxygenated solutions at natural, near neutral pH. Combination potentials established between the mineral-grinding media pair were simulated by applying a potential of -0.455 V (vs. a standard hydrogen electrode) either to a pyrrhotite or to a chalcopyrite electrode. Chronoamperometry was used to study the polarization behaviors and alteration of mineral surfaces through cathodic processes. The kinetic parameters of cathodic decomposition of pyrrhotite and chalcopyrite were determined and compared. It was concluded that pyrrhotite decomposed faster than chalcopyrite in near-neutral pH solutions. Both minerals were then covered by a film consist¬ing mainly of iron hydroxides, which adversely affected their flotation.

Jan 1, 1999

By Shuji Owada, Keisuke Yasukawa

Electrostatic and/or high tension separation has been used for the separation of rare metal bearing minerals, foods, industrial wastes and so on. Since the separation is achieved by the difference mainly in surface conductivity of particles, the efficiency in humid circumstances is very low, and then, the applicability is considerably limited. We applied the following two-stage pretreatment technique to the separation process, which involves (1) adjustment of surface wettability by adsorbing surfactant on the particle surface and (2) control of the surface conductivity by spraying with electrolyte aqueous solution. The addition of this pretreatment technique has been found to have a great advantage over conventional methods. Separation efficiency is achieved even in humid circumstances and selectivity can also be obtained between insulator minerals. The selectivity is very similar to that of flotation in wet process. This separation technique will be applied not only to mineral processing but the processing of industrial waste such as electric and electronic waste materials.

Jan 1, 1995

By S. Ersayin, I. Iwasaki

Laboratory- and pilot-scale tests were carried out to study the effects of a magnetically enhanced hydroseparator on a magnetic taconite sample. The test parameters included feed flow rate, percent solids and magnetic field strength. Laboratory tests showed that magnetic iron losses could be effectively prevented by applying a magnetic field strength of 0.003 T (30 gauss) to a hydroseparator. A relatively uniform magnetic field within a pilot-scale hydroseparator was obtained by installing a magnetic grid within the device. The test parameters for the pilot-scale study also included the effects of magnetizing/demagnetizing the feed and magnetizing current. Magnetic iron losses were substantially reduced, even when the hydroseparator was operated at very high upward velocities. Results also show that increasing the field strength decreased the losses, but magnetic enhancement was successful even at the lowest field strengths, and the results show that magnetic iron losses were lower when the feed was magnetized. Key words: Hydroseparator, Magnetic field, Magnetic grid, Taconite processing, Magnetizing, Demagnetizing.

Jan 1, 2003

By Walker Ian W., John D. Gow

The paper describes the exploration and development activity associated with a series of open pit gold deposits in the Laverton region of Western Australia with an aggregate resource base of 4 million tonnes at a grade of about 3 grammes per tonne. In September 1988, Hill Minerals N.L., now a wholly owned subsidiary of Ashton Mining Limited, completed the purchase of the Cork Tree Well treatment plant from Austwhim. This CIP plant had a rated capacity of 235,000 tonnes per annum, and is located within the Hill Minerals Laverton Project area. Ore is trucked by haulage contractors from each open pit mine to the central treatment plant at Cork Tree Well. Studies were completed and a plant expansion undertaken lifting throughput to 500,000 tonnes per annum. A contract was let for this expansion in November 1988, and construction completed in April 1989. Concurrent with the above project development work, heap leach metallurgical studies are being undertaken on low grade mineralisation associated with higher grade ore zones at several of the open pit mines, notably King of Creation and Craiggiemore. It is anticipated that heap leaching will provide a useful adjunct to gold production from milling higher grade ores.

Jan 1, 1989

By L. W. Saperstein

In this paper, a number of novel hypotheses that provide a fresh perspective on the characterization of strata movements associated with longwall mining are developed by analyzing subsidence measurements with an influence-function-based computer program. Using an inverse application of the traditional influence-function technique, easily obtained surface displacements are used to analyze some of the complicated, expensive, and difficult-to- measure movements of the intermediate roof strata in a longwall panel. The primary hypothesis developed by this analysis proposes the existence of an area of partial roof caving near the edge of a panel called the "edge effect." A secondary hypothesis, interrelated with the first, promotes the importance of the effect of gate-entry closure on the observed strata movements. Both the primary edge-effect hypothesis and the secondary hypothesis concerning gate-entry closure are justified and quantified in an extensive analysis of surface subsidence that uses supporting information from related theories, design criteria, and in situ measurements. Next, the edge effect and the gate closure hypotheses are extended further and used to provide an explanation of the complex subsidence interaction of adjacent longwall panels in what is termed a "redisturbed" effect. Finally, the importance of accurately understanding these longwall strata movements for proper subsidence prediction or gate design is stressed.

Jan 1, 1988

By David M. Mchaina, Allan E. Hall, Siegfried Rohr, J. D. Botsford

Incidents associated with secondary dust ignitions in the mining of massive sulphide ore deposits are of major concern in Canadian underground metal mines. During stope or development blasting, a highly concentrated cloud of sulfide dust is created and may be ignited, resulting a secondary explosion which releases a considerable volume of sulphur dioxide and possibly other sulphur gases. The consequent pressure, heat and toxic gases can result in loss of life, significant damage to equipment and loss of production. These losses are expensive and should be prevented. Explosions of this type have occurred at the H-W mine of Westmin Resources mainly in the development headings and cut and fill stapes. This paper presents the results of a study conducted at the H-W mine to compare dust sampling methods for explosivity tests. The associated benefits and pitfalls of each sampling technique are examined. The investigative work conducted to develop and test preventive and control methods against sulphide dust ignitions is also discussed. The techniques which will minimize the risk of sulphide dust ignition in metalliferous mines are outlined. A review of current preventive and control measures practised at the H-W mine is also presented.

Jan 1, 1989

By John E. Urosek, Jack E. Tisdale

The Mine Safety and Health Administration (MSHA) has developed a Mine Ventilation Bleeder and Gob Training Course. This three day course is designed to increase the knowledge and understanding of bleeder ventilation systems. It discusses concepts, designs, plan approval, inspection and evaluation of bleeder systems. This paper will introduce some of the material contained in that course, focusing on the inspection, examination, and evaluation of bleeder systems. The regulations addressing the use of bleeder systems are found in Title 30 Code of Federal Regulations (30 CFR) Section 75.334. The examination requirements are found in 30 CFR Section 75.364. Section 75.364 de- scribes specific locations where examinations are to be made and specific information to be gathered at those locations. The required locations and information will be discussed in some detail with examples and illustrations. These weekly examinations for bleeder systems are designed to monitor the parameters of the bleeder system and to evaluate its effectiveness. Over time, conditions can develop in the bleeder system that affect the ventilation and lead to hazards such as methane accumulations. The hazards of methane accumulations need to be understood as such accumulations can contribute to mine explosions. The importance of additional information gathered by the mine examiner that can assist in evaluating the performance of the system will also be discussed.

Jan 1, 1997

By Lynn B. Hales, Randy A. Ynchausti, Robert W. Colby

Process control systems have evolved from single loop control to distributed control with computer based expert control strategies. The next step is to add adaptive control to the expert control strategies. An object-oriented intelligent adaptive optimization approach is defined and simulated results are presented.

Jan 1, 1995

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 S. Bozinis

In this paper, blast design considerations and implementation that lead to reduced vibrations will be presented. In addition, blast vibration data collected during hard and semi-hard rocks blasting in the proximity of an inhabited area will be analyzed and presented. In all cases maximum vibration levels are kept below the limits set by DIN 4150.

Jan 1, 2006

By Pertti Koivistoinen

There are many grinding schools in the mining world, which claim their grinding method to be the best possible - and still the methods concerned vary a great deal. Some of them have multi- stage crushing and only single stage grinding while in others crushing may be nominal, but grinding can be very complicated. - In this presentation firstly the nine most common comminution circuits will be analyzed. Then results from a pilot scale test series will be reviewed, in which nickel ore ground by four different comminution methods was fed to a common flotation treatment.

Jan 1, 1995

By James A. Everts

Calcined bauxites are classified by their major end uses - abrasives and refractories. Target properties are dictated by application and processing requirements. The chemical and physical properties of premium grade calcined bauxites are far more stringent than metallurgical bauxite and this limits the sources and availability. Premium grade calcined bauxites are considered to be strategically critical to the industrialized countries of the world. Subject to disruptions in the key source countries, adequate supplies of premium grade calcined bauxites are anticipated in the foreseeable future.

Jan 1, 1984

By J. G. Jenkins

Magma Copper Co.'s San Manuel solvent extraction/electrowinning (SX-EW) facility has operated since May 1986. The original facility had a design capacity of 22.6 kt/a (25,000 stpy) of electrowon copper cathode produced by processing pregnant leach solution from an open pit-heap leach operation. In 1988, the plant was expanded to 45.3 kt/ a (50,000 stpy) to incorporate processing in-situ leach solutions. This pager focuses primarily on the heap leaching area with regard to exploration, testing, feasibility, permitting, design and construction, and operating practices. Research using surfactant leaching aids to enhance copper recovery is also discussed.

Jan 1, 1995

By D. W. Fuerstenau

Experiments using an optically polished Pyrex disk and aqueous dodecylammonium acetate (DAA) films showed that the velocity with which the films recede increases markedly if the runs are repeated at short time intervals, where equilibrium cannot be reattained. This results from DAA molecules being desorbed from the disappearing liquid-air interface and being deposited on the solid-air interface being formed. Controlled experiments with Pyrex particles in a modified Hallimond tube showed a similar increase in flotation rate, again due to excess adsorption of DAA molecules that were transferred to the solid-air interface from the bubble on contact.

Jan 1, 2002

A number of factors affecting the properties of cemented aggregate fill (CAF), particularly its strength development have been studied through a series of laboratory investigations carried out at the Western Australian School of Mines in the Western Australia in recent years. The outcomes of these investigations indicate that apart from cement dosage, aggregate particle size distribution, aggregate quality, additional fine materials, water salinity, admixture dosage and sample scaling all contribute significantly to the development of cemented aggregate fill strength.

Jan 1, 2001

By G. X. Wang, J. O. Marsden, M. C. Fuerstenau

Zinc cementation of high-temperature carbon eluates is now used extensively in gold processing to replace electrowinning. Under these conditions, zinc consumption is high. In this paper, zinc solubility is press rated us functions of temperature, cyanide concentration and pH in the presence of gold, silver and mercury cyanides (both individually and in combined solutions). Based on the experimental results, cementation of these metals is characterized and discussed. The importance of cyanide concentration in cementation efficiency and the effect of mercury and its co-precipitation onto zinc are also discussed.

Jan 1, 1997

By James P. Rider, Charles D. Taylor, Edward D. Thimons

Research was conducted to investigate how ventilation of a mining face is affected when scrubber flow is greater or less than intake flow. Tests were conducted in a full-scale surface test gallery built to simulate a mining entry with a continuous mining ma- chine at the face. Methane gas was released at constant flow at the mining face. Gas measurements taken at six locations near the face were used to evaluate how well the face was being ventilated. Increasing scrubber flow resulted in lower methane levels even when scrubber flow was much greater than intake flow.

Jan 1, 1997

By P. J. Kientzler, Y. C. Lo

The current study is concerned with the analysis and attempt at simulating the product size distributions obtained from a vibrating ultrasonic device. Systematic experiments of comminution were performed with natural sizes as well as monosizes in order to understand the breakage behavior of the device. A precise analysis of the device's breakage performance in the case of fine grinding of alumina samples will be presented. Initial steps to model the breakage events using a detailed mathematical algorithm will be discussed.

Jan 1, 1992