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By José A. Rios, José A. Vidalôn

The case study of a highland area in the Central Andes of Peru, where many abandoned polymetallic mines are found, is presented. Some of these mines generate metal leaching and acid rock drainage (ML/ARD) or have potentially ARD generating (PAG) tailings/waste rock storage. Effluents are discharged into the first of two lakes in line, which act as reservoirs for irrigating an important valley in the desert coastal region. Drainage fees, their relationship with the deposit and the solid-wastes mineralogy are discussed, as well as variations in water and sediments composition, the benthos, and the aquatic/riparian flora/fauna in these lakes.

Jan 1, 2000

By Nathaniel Arbiter

Flotation’s earliest patent was issued in 1860. However, the process was first applied commercially in Australia until 1904, and in Montana in 1911. Major advances followed both in reagent treatment and in cell design, with resulting process improvements. Mechanical cells have seen the widest use and with the major increases in plant capacities (Fig. 1) their volumes have also increased (Fig. 2). In 1991, the principal use for the process was to produce copper concentrates for smelting. It was applied to 243 Mt (268 million st) of copper ore. The total of all ores floated that year was 426 Mt (470million st). In 1997, US mines produced 257 Mt (284 million st) of copper ores for flotation, yielding1.75 Mt (1.94 million st) of copper.

Jan 1, 2000

By K. Hanumantha Rao, K. S. E. Forssberg, H. R. Manouchehri

The fundamentals of electrical separation, the electrical properties of minerals, the principal methods used for charging minerals and their mechanisms, the effective factors controlling the acquisition of charges by minerals, the general configuration of commercial electric separators and the forces operating during electrical separation of minerals are reviewed and presented.

Jan 1, 2000

By W. P. Diamond, S. L. Cario, F. Garcia, J. D. Byars, T. P. Mucho

The National Institute for Occupational Safety and Health (NIOSH) has been conducting research at a Pittsburgh Coalbed longwall mine to evaluate and optimize bleeder ventilation and gob gas venthole longwall methane control systems. Gas flow into these two methane control systems was investigated using a combination of Sulphur Hexafluoride (SF6)tracer gas studies and gob venthole pressure monitoring experiments. The insights gained from this research has facilitated the development of a longwall subsided strata methane control system conceptual model. This model provides the basis for design suggestions to increase the efficiency of the gob gas venthole system to permit the bleeder ventilation system to become a "safety net" for methane control.

Jan 1, 2000

By Kevin Sharman, Peri Mehling

A detailed assessment of acid rock drainage (ARD) potential was conducted at the Quintette Coal Mine site in northeastern British Columbia The site is unusual in that the coal seams contain low sulphur levels as compared to eastern coals (typically less than 0.5%), and the non-coal wastes generally do not to have the potential to generate acid on the basis of static ABA tests. The presence of small iron-stained seeps on the pit walls indicate localized sulphide oxidation, while the overall mine site drainage has remained of excellent quality with extremely low levels of metals after approximately 15 years of mining. Thus the site provides an excellent comparison to more problematic coal mine sites. For the Quintette assessment, static acid-base accounting (ABA) analyses of individual samples were compared to criteria for potentially acid generating materials developed for the U.S. Appalachian coal, as well as criteria developed in British Columbia for hard rock mines. Geologic units were characterized by the percentage of samples, or weighted thickness, that was deemed potentially acid generating (PAG). Links were then made to actual seepage and water quality emanating from geologic units around the site. Seeps at the site demonstrate a large range in pH (2.32 to 8.18). The few acidic seeps (pH < 4.0) were found to contain elevated levels of sulphates, dissolved iron, manganese and aluminum, consistent with the metals typically of concern in Appalachian coal mines. Other heavy metals that were detected in acidic seeps at Quintette included copper, zinc, nickel and cadmium. The use of simple ABA tests, and comparison of individual sample results with the Appalachian and British Columbia criteria, was found to be useful in predicting the probable sources of the small localized acidic seeps.

Jan 1, 2000

By H. L. Ehrlich

Marine manganese nodules harbor a mixed population of manganese-oxidizing and -reducing bacteria, as well as bacteria that do not act on manganese. They also host phagotrophic protozoa. Out of several laboratory studies, one line of investigation indicates that some kinds of bacteria found on nodules can catalyze the oxidation of Mn2+ bound to Mn(IV) oxide at the surface of nodules at in situ temperature and pressure. In the absence of appropriate bacteria, the rate of oxidation of the surface-bound Mn2+ is significantly slower. How Fe(III) is incorporated is still unclear. Base metals such as Cu, Ni and Co, which are usually found in marine nodules in various quantities, may be incorporated through scavenging by Mn(IV) oxide. Laboratory evidence shows that some other bacteria on nodules can reduce the Mn(IV) oxide to Mn2+ in the presence of an appropriate source of reducing power in the form of organic carbon. The reduction of Mn(IV) oxide mobilizes manganese and trace metals such as Cu, Ni, and Co in the nodules. These bacteria reduce Mn(IV) whether oxygen is present or not. They could be harnessed in the bioleaching of nodules. The manganese(IV)-reducing bacteria and the bacteria that neither oxidize nor reduce manganese are thought to keep the organic matter in the nodule environment sufficiently low to favor bacterial manganese-oxidation, which in laboratory tests is inhibited by excess organic carbon. The preying by the protozoa on the different kinds of bacteria is thought to control the bacterial population on nodules and ensure continued growth of the manganese-oxidizing bacteria and the nodules. To eliminate interference from seawater salts in the bioleaching of Mn, Cu, Ni and Co, it may be more advantageous to use terrestrial Mn(IV)-reducing bacteria than the Mn(IV)-reducing bacteria resident on nodules. The terrestrial bacteria would allow bioleaching in fresh water. Unlike the marine bacteria, most terrestrial bacteria studied to date reduce Mn(IV) oxide only anaerobically. A general outline for an anaerobic bioleach process of marine nodules with freshwater bacteria is discussed.

Jan 1, 2000

Syncrude Canada produces a large part of Canada’s crude oil supply. The company processes about 225,000 bbl/day. The oil produced is used for jet and automobile fuel, home heating oil, plastics and other consumer synthetics. Crude oil is produced through a process of mining, extracting and upgrading bitumen. A rich supply of bitumen is contained in the Athabasca oil sands deposit in northern Alberta. Tailings from the bitumen processing are sent to a settling basin.

Jan 1, 2000

By A. M. Alfantazi, R. R. Moskalyk

Over the years, improvements have been made in the recovery of nonferrous metals, including improvements in the areas of mineral processing, pyrometallurgy and hydrometallurgy to extract cobalt as a byproduct from host minerals containing mainly nickel, copper and associated precious metals. At present, the technological emphasis is on solvent extraction coupled with electrowinning (SX-EW) for lateritic sources of supply within the Southern Hemisphere, such as in Australia and New Caledonia. Although sulfide-bearing ores, such as those found in Canada and Russia, will serve as a viable long-term source for cobalt, a ubiquitous metal, the future trend is anticipated to be in the implementation of compact and efficient SX-EW facilities that apply state-of-the -art innovation with environmental compliance This paper serves to collate the known practices for the recovery of market-grade cobalt by means of electrowinning from either an aqueous sulfate medium or chloride medium after upstream leaching, solvent-extraction and solution-purification procedures. For completeness, other commercial production techniques for the recovery of cobalt as a sulfide or oxide product are included in the summary of current cobalt processing practices.

Jan 1, 2000

By Henry Brehaut

The International Network for Acid Prevention (INAP) was formed in 1998 by 17 international mining companies to promote significant improvements in the management of sulphidic mine materials and the reduction of liability associated with acid drainage through knowledge sharing and research and development of technology. Since its inception two panels have been formed to identify and move forward with research projects and eight networks have been constituted to initiate interaction and knowledge sharing within the membership in specific areas of technical interest. An INAP web site has been developed to facilitate the sharing of information and to encourage the exchange and development of new ideas.

Jan 1, 2000

By R. D. Lawrence

Suggestions have been made that the appraisal of mining assets using discounted cash flow techniques should be based solely on proven and probable reserves in reliance upon the widespread international recognition of uniform resource definitions. Following a review of general accepted valuation principles, a survey of the literature and, most importantly, a review of real transactions in the open market, it is clear that valuators should not be constrained by the growing acceptance of modern mineral resource codes. On the contrary, valuation practitioners should be encouraged to examine all classes of mineralization and, after making due allowance for risk, to utilize all mineral resources as a basis for determining fair market value.

Jan 1, 2000

By Graham Taylor, Mandy Agnew

Hardpans developing in tailings storage facilities (TSF) in Australia have been investigated in relation to Acid Rock Drainage (ARD) generation. This research had three main aims. Firstly it was to obtain an understanding of the physical and chemical characteristics of tailings residues which support the in-situ formation of cemented layers and hardpans. Secondly it was to examine how effective hardpans are at reducing ARD generation, and thirdly it was to investigate the promotion of hardpan formation to inhibit ARD and pollutant generation. This paper presents the data collected during investigations into the effectiveness of hardpans to reduce ARD generation. Three basic types of hardpans have been identified and examined: laterally extensive surface hardpans, laterally extensive cemented layers; and laterally discontinuous hardpans developing in locations of seepage. Their mineralogy, morphology, lateral extent, depth and rate of formation are dictated by sulfide and gangue mineralogy and content, milling and depositional techniques of the tailings and the climate. As the sulfides oxidise, acid and heavy metals are generated, while gangue mineral degradation is enhanced, adding to elemental loads. These liberated ions are then available for precipitation of secondary mineral cements through concentration during evaporation. In TSFs where hardpan development is restricted by mineralogy, grain size or climate, hardpan formation can be enhanced in seepage zones (eg. seepage from waste rock dumps) where tailings are exposed to seepage waters laden with heavy metals and sulfate. The effectiveness of hardpans in the inhibition of ARD generation is dependent on reducing oxygen diffusion and water infiltration into the underlying tailings. A reduction in water infiltration will diminish the transport of contaminants developed during sulfide oxidation and subsequent reactions. Water and gas movement through the hardpans at the CSA (Cu, Zn, Pb) and Elura (Pb, Zn, Ag) mines has been investigated. Permeability tests indicate the hardpans have reduced the infiltration rates by 10 to 100 times that of the fresh tailings. Oxygen diffusion rates were calculated and were shown to be up to 1000 times lower in hardpans than in fresh tailings. Such decreases are explained by persistent elevated &apos;degrees of saturation&apos; within the hardpans. These conditions were verified using a conceptual model of sulfide oxidation reactions, which allowed comparisons of diffusion coefficients with modelled and observed depths of oxidation within the tailings impoundments.

Jan 1, 2000

By J. M. Mutmansky, Y. J. Wang

The method usually used to predict the direction of flow in a connecting airway is to conduct a survey of the two existing nodes to be connected by the new pressure airway. It is then assumed that the air will flow from the node with the measured higher pressure to the node with measured lower pressure. This paper examines this direction-of-flow problem using properties of the system characteristic curve for a two-terminal network and specifies some conditions that will ensure that the air will flow in the direction anticipated. It was concluded that the only requirement is that all characteristic curves of the fans in the network should be strictly decreasing. Five numerical examples illustrate some important proper- ties of the direction-of-flow problem.

Jan 1, 2000

By Paul Mitchell, Clive Potter, Miles Watkins

Meldon Quarry is a seemingly rare occurrence of acid rock drainage (ARD) in a quarrying operation.4 With surface waters discharging to a tributary of a salmon-bearing river, it is subject to stringent discharge conditions. The quarry predates effective environmental management, and preventative, control and treatment measures were not implemented until relatively recently. However, retrospectively implementing standard preventative approaches at the site is costly, technically difficult and of uncertain benefit. This paper overviews the recent site history and introduces data from a demonstration by KEECO (UK) Limited of its Silica Micro Encapsulation (SME) water treatment technology.

Jan 1, 2000

By James A. Brierley

The author has known Professor Wadsworth since the 1960s, when interest in the application of microbial technology for metallurgical processes was beginning its rapid rise. The development of bioleaching and mineral biooxidation was advanced, in part, by Wadsworth&apos;s belief in the potential for its application, as well as by his numerous contributions to the understanding of the fundamentals of hydro-metallurgy. Wadsworth is recognized for fostering research and development of the field and adding credibility to microbiological-based metallurgical processes, now often referred to as biohydrometallurgy. This Wadsworth Award is recognition of the field of biohy-drometallurgy. It is an honor to serve as a representative for all those individuals involved in research and commercial development of this technology. Modern commercial application of biohydromctallurgy began with the bioleaching of copper from submarginal-grade. run-of-mine material. Kennecott Copper successfully developed this process in the 1950s at the Bingham Canyon Mine in Utah. Other mining operations around the world followed Kennecott&apos;s lead. Today, dump bioleaching remains a very low-cost process for scavenging copper from rock that cannot be economically processed by any other method. Despite the commercial success of dump bioleaching, little effort has been made to enhance the micro Biological component of this leach process. Expansion of biohydro metallurgy into recovery of other metals did not occur until the mid-1980s, when the first commercial plant for the pretreatment of refractory gold-bearing concentrate was commissioned at the Fairview operation in south Africa. Now, processes for copper bioleaching and refractory gold pretreatment are engineered specifically to promote the activity of the microorganisms. This paper reviews the current state of commercial applications of biohydrometallurgy. It examines potential future developments and portrays the role of the microbiologist in facilitating continued growth and commercial acceptance of the technology. The commercia1 examples in this paper illustrate the expansion of microbial processing in the mining industry during the last 20 years. Copper bioleaching Early commercial applications of bioleach technology involved processing submarginal-grade, copper- bearing, run-of- mine rock in dumps. Recent applications of the technology use engineered bioleach heaps. Currently. all of these operations are in the Southern Hemi-

Jan 1, 2000

By J. Tuzson, H. McL. Clark

Introduction Wear of pumps, wet cyclones and pipelines by suspended solid particles will impact their operating economies by limiting their useful life, reducing their reliability and increasing the amount of servicing. Erosion is considered a materials problem. The empirical solution consists of testing different materials in field applications. Such tests are time consuming and expensive. The prediction of localized wear rates, life estimates and appropriate material selection demand a better understanding of the slurry wear process in environments corresponding to those found in working equipment. Key words: Wear, Slurry abrasion, Coriolis erosion tester The slurry wear process Solid particles suspended in liquid generally move with the flow, but such particles deviate under the centrifugal and Coriolis forces encountered in pumps. The concentration of particles will increase, and a solid layer or bed may accumulate if the acceleration is directed against the flow passage wall. Large particles in dilute suspensions may impact the wall. dissipating their kinetic energies and removing material. However, particles smaller than about 11)(1 µm encounter great drag when moving through the liquid. and such par¬ticles have little kinetic energy left when they reach the wall. They cannot penetrate the stagnant boundary layers present in pumps. Therefore, small particles tend to form beds that slide along the wall, removing material by a process that could he called sliding erosion or wet abrasion. Wear by impact erosion from large particles in dilute slurries can he predicted by appropriate analytical and empirical methods. However, laboratory tests and calculations of wear rates that correspond to sliding erosion are more likely to correlate with field experience from wear under similar conditions. Specific energy Data from laboratory slurry erosion experiments have shown that the amount of material removed is approximately in proportion to the energy expended in the erosion process. Thus. the specific energy-energy expended in removing by erosion a unit volume of material-offers a simple, practical measure for the erosion resistance of materials. The concept was found to also apply to sliding erosion (Clark et al.. 1997). Generally, the study of the material-removal process in slurry erosion continues to remain a subject of research. Conceptually, if the flow velocities and accelerations could be calculated in a pump or pipeline, the energy dissipated at the passage walls could also be estimated, and the material removal rate would become known from the specific energy determined by laboratory tests. Slurry erosion testing Laboratory devices made specifically for slurry erosion testing may be grouped into the following: jet erosion devices, slurry pots and the Coriolis test machine (Pagalthivarthi and Helmly, 1992). Jet erosion devices use a slurry pump and nozzle to produce a high-velocity slurry jet that is directed at a flat material specimen, either perpendicularly or at some acute angle. Combined impact and sliding erosion are produced. but the processes cannot be separated, and the wear is difficult to assess except by weighing. Slurry pots consist of a cylindrical vessel containing the slurry of interest. In the slurry pot, test specimens are attached to a rotating arm. The samples are rotated in the slurry and experience local flow conditions that result in combined impact and sliding erosion. Wear depth measurements from detailed laboratory experiments have been successfully correlated with results from an analytical model of the process, and specific energy values have been calculated (Wong and Clark, 1995). In industrial use, the samples are weighed to determine the total material loss. Materials are ranked with respect to some reference material. The Coriolis erosion tester (Tuzson, 1984) consists of a rotor with a central cavity, from which two opposing radial passages lead out (Fig. 1). The slurry is fed to the centerof the rotor in one pass from a stirred overhead tank. The slurry particles are subjected to the Coriolis acceleration as they flow out through the radial passages. The material specimens are mounted into the radial passage walls facing the direction of rotation and are eroded by the particles that are pressed against them as they flow out radially. A narrow groove is worn into the sample within a few minutes, using a few gallons of slurry. Material removal is estimated accurately from profilometer traverses across the wear scar at different locations. The energy dissipated by the particles can be estimated, which leads to a well-defined experimental value for the specific energy.

Jan 1, 2000

By J. A. Flinn

Phelps Dodge’s Morenci copper mine has had six drills, six track-dozers, 16 shovels, two loaders, and 90 haul trucks equipped with either Caterpillar, Aquila, or Modular GPS systems for nearly three years. The Caterpillar Computer-Aided Earthmoving System is an open-architecture system, which allows for inputs to enhance orientation solutions and system functionality. This system has begun a new phase that leads to an intelligent mining system. Optimization techniques of the current system and inputs are reviewed. In addition, some practical issues of implementing new technology in a mining environment have been identified to aid in this new phase.

Jan 1, 2000

By Nico Bezuidenhout, André M. van Niekerk, Jan J. G. Vermaak

This paper documents empirical evaluations of geochemical data that was recorded during a seven year pilot scale experiment. The experiment was aimed at assessing the effectiveness of natural soil covers for rehabilitation of coal discard facilities. Ten test cells were constructed using different natural soil cover materials and configurations. Results of the evaluation indicate that, although a pH breakthrough was not recorded for the single layer soil cover cells as was the case with the uncovered cells, single soil covers were not effective in preventing ARD oxidation processes. Multi layered soil covers were found to be able to create anaerobic conditions leading to a reduction in ARD oxidation processes and an improvement in leachate quality.

Jan 1, 2000

By R. P. Killmeyer, W. W. Wen, B. K. Parekh

A continuous pilot-scale test of the GranuFlow Process was conducted using a screen-bowl centrifuge for the dewatering and reconstitution of column -flotation concentrate at a coal preparation plant in Virginia. In this test, a slipstream of the fine clean-coal slurry from the column flotation con¬centrate was treated with a bitumen emulsion before dewatering. The treated products from the screen-bowl centrifuge appeared to be dry and in a free flowing granularform, while the untreated products were wet, sticky and difficult to handle. Test results indicated that the average moisture contents of the dewatered coal products were 35.7%, 35.5%, 32.6%, 29.9% and 26.5% (by weight) with Orimulsion additions of 0.0%, 0.7%, 3.2%, 4.8% and 6.4% (by weight), respectively. The handleability and dust reduction of the dewatered coal products were also vastly improved.

Jan 1, 2000

By Rajive Ganguli

There are several elements of online pedagogy and information technology that are being used in the University of Alaska Fairbanks’(UAF) course “ES 201: Computer Techniques,” to enhance classroom teaching. The use of information technology in this class grew from a desire to make lecture notes available to students. This has grown to include a sophisticated, online delivery software package. It provides chat rooms, discussion groups, and online testing and grading. Online delivery aside, the class uses the telnet, e-mail and C++/FOR-TRAN compiler facilities of the university server during class to enhance learning. During class, for example, the students read the lecture notes on the Web browser, telnet to their university Unix accounts, check their e-mail and download programs (to be covered in class) sent by me, and then compile, run and modify the programs. The class, therefore, requires students to be active most of the time. This ensures their full attention and better learning due to the hands-on experience (Fig. 1).

Jan 1, 2000

Little knowledge is available that considers the effects of continuous miner position on the possible respirable dust exposure of the remote mining-machine operator. Such information could be very useful for increasing the awareness of the remote operator as to those parts of an extended cut that generate higher levels of respirable dust. This data could be used to develop guidelines for positioning the remote operator to reduce his potential exposure. This work details the effects of continuous miner position on dust levels measured on the machine and at the remote continuous miner operator location.

Jan 1, 2000