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Mine reconciliation is the practice of comparing the tonnage and grade of material processed by the mill with the tonnage and grade of ore in the reserve model of a deposit, and with the tonnage and grade in the grade control models used to de

Jan 1, 1998

By R. Canello, J. Jenkins

El Abra has the world's largest leach, solvent extraction and electrowinning facility, The crushing plant capacity is 120,000 metric tonnes per day and the cathode production capacity is 225,000 metric tonnes per year. The El Abra mine and plant are located in the Province of El Loa, in Region I1 of Chile, 55 km. north of the city of Calama. The ore deposit outcrops on the southern slope of Cerro Pajonal at an altitude of 3,900 to 4,100 meters above sea level. The processing plant and camp facilities are located at a lower 3,300 meter elevation on an alluvial slope, 15 km southeast of the deposit. The operating company, Sociedad Contractual Minera El Abra, is 51% owned by Cyprus Arnax Minerals Company through the Cyprus Climax Metals Company subsidiary and 49% owned by Corporaci6n Nacional del Cobre de Chile (Codelco). The present paper describes the ore reserves, mine operations, crushing, leaching, solvent extraction, electrowinning and infrastructure facilities.

Jan 1, 1998

By Paul B. Harder

Round Mountain Gold (RMG) in cen­tral Nevada, reports that over a nine-year period and a million operating hours, its fleet of 150-ton and 190-ton haul trucks has averaged better than 93% availability, with some of the trucks approaching 70,000 operating hours. Repair costs have been far below industry averages. Mine operations manager Pete Kesl credits the high availability and low repair costs to a succession of Product Support Agreements between RMG and Caterpillar dealer Cashman Equipment. He adds that good equipment and a high level of trust and co­operation between all parties to these agreements have been essential to their success at Round Mountain.

Jan 1, 1998

By Chikabumi Yamauchi, Mitsuru Tanahashi, Toshiharu Fujisawa

"Thermodynamic properties of impurities in molten silicon are of prime importance in developing economical production methods of solar grade silicon. In the present research work, thermodynamic properties of boron, the most difficult element to remove from molten silicon, were measured by chemical equilibration techniques at 1723 and 1773 K. Activity coefficients and self-interaction parameters of boron in molten silicon were determined by equilibrating the melt with solid BN under controlled nitrogen partial pressures. Interaction parameters between boron and nitrogen in molten silicon were also determined by equilibrating the molten Si-B alloys with solid Si3N4• Based on the data obtained, the stability diagram of the Si-B-N system was established.IntroductionPhotovoltaic power generation using a silicon solar cell is expected to be the most promising energy source, because it is inexhaustible, cleaner and more safety than conventional energy sources, such as thermal or atomic power generation. At present, expensive off-grade silicon for semiconductor (SEG-Si) is used for a solar cell production. However, if a large-scale photovoltaic energy conversion using silicon solar cell comes into wide use in the near future, silicon will be sure to be in short supply for the cell. Therefore, a development of a new large scale process for solar grade silicon (SOG-Si) production is definitely necessary, which can remove contained impurities from silicon.Among the impurities contained in silicon, boron is one of the most difficult ones to remove by a zone melting or an unidirectional solidification, because its segregation coefficient in silicon is close to unity (0.8). In addition, boron behaves as a p-type silicon semiconductor dopant and, therefore, its content in SOG-Si must be severely controlled. Although some attempts to remove boron by various metallurgical methods have been carried out [I -4], quantitative analysis has not been made due to lack in the information on the thermodynamic properties of boron in molten silicon. From this view point, the activity of boron in molten silicon was determined in the present study by chemical equilibration techniques at 1723 and 1773 K."

Jan 1, 1998

By F. T. Principe

In order for solvent extraction technology to be acceptable as an alternative to existing jarosite precipitation circuits, iron must be cleanly separated and concentrated into a feed stream suitable for downstream iron by-product recovery which meets market specifications and economics. Ten years ago, significant progress was made in a joint McCill University/CANMET project that involved iron extraction with mono(2-ethylhexyl) phosphoric acid and stripping with HCI. Our iron solvent extraction research was reactivated recently by looking into this and other members of the organophosphorus extractant family. Our research focuses on the mechanisms and control of anion (SO42/CI) transport across the various phases (Rafinate/Organic/Strip), iron build-up in the strip liquor, and extractant stability/selectivity. In this paper, these issues along with some other performance parameters are discussed using data derived from an extensive search of the two commercially available and best known members of the organophosphorus family, di-2-ethylhexyl (D2EHPA) and mono-2-ethylhexyl (M2EHPA) phosphoric acid. Further in this discussion, the challenges lying ahead in the development of sx systems that overcome the deficiencies of D2EHPA and M2EHPA are outlined. In particular, the necessity of considering secondary separation technologies that can further concentrate iron values in the chloride strip liquor to levels economically attractive for the production of saleable iron oxide by pyrohydrolysis is addressed.

Jan 1, 1998

The estimation of the shear stress distribution around an excavation is important to the design of the excavation since shear stresses can generate cracks, loosen grain boundaries or otherwise degrade the mechanical and physical properties of the rock and lead to stability problems. In this study, the distribution of shear stresses in a pillar were back-calculated from the deformation measurements made from the SPDV (Site and Preliminary Design Validation) area at the Waste Isolation Pilot Plant (WIPP) site. A plausible pattern of shear stress around an excavation has been suggested based on the Zero Strain Boundary (ZSB) calculation, computer simulation using FLAC, and back-calculation using measured deformation rates in the pillars.

Jan 1, 1998

By Kathryn Hindmarsh

The most common method for the concentration of cyanide in gold leach circuits is based on the titration of cyanide ions with silver ions. This can either be done manually as a titration with a visual end-point or by using one of several commercial cyanide analysers which are 'based on the same titration but use a potentiometric end point This method has 'its limitations in the case of some ores such as those containing high amounts of soluble copper and those that are treated at low (less than pH 9) pH values in that the titration results do not accurately reflect the concentration of cyanide which is available for the dissolution of gold. This paper will present the results of the development of a novel "active" cyanide analyser which is based on the rate, of the reaction between gold colloids and cyanide. Gold colloids have a deep red colour and can be very simply prepared and stored for extended periods of time when stabilized. t has been shown that colloidal gold behaves similarly to metallic gold, dissolving in aerated sodium cyanide solutions to give the colourless Au(CNh-ion, This allows the reaction between the colloids and cyanide to be monitored spectrophotometrically at 520 nm. An automated instrument has been developed around this concept which can analyse a filtered pulp stream every few minutes with periodic calibration using standard cyanide solutions, Results of test work on synthetic solutions and solutions derived from several Australian gold plants will be presented as will the results of a comparative evaluation with a commercial titration analyser on a local gold plant

Jan 1, 1998

By P R. Lock

The Silver Swan nickel mine is located at the Black Swan Nickel Project, 53 km north east of Kalgoorlie, Western Australia. The Silver Swan orebody is a massive sulphide nickel deposit dipping 70¦ east with an average in situ grade of 14 per cent. Mining of the massive orebody is by Mechanised Ramp Cut and Fill (MRCF). A mining recovery of 98 per cent and minimising dilution are primary goals in extracting the high-grade ore. Placing a distinguishable marker bed (working platform) on rock fill was identified as a key method to achieving these goals. Gravel from a pit located onsite was considered the most suitable material for the marker beds. Research undertaken to design the marker beds using the gravel revealed conventional methods used in mining would not suffice, but that road stabilisation methods could be a viable alternative. Trials used a road recycler to mix cement and gravel in situ and several test beds were constructed on the surface to determine the final design. The trials attempted to replicate a marker bedÆs life cycle of construction and placement and mucking of ore from the marker bed. Testing the marker bed for strength for use as a working platform was completed using a Clegg Hammer; good correlation to a Clegg Impact Value and the compressive strength of the stabilised gravel was found. This paper describes the use of a road stabilisation machine, tests conducted, monitoring and marker bed design and discusses underground placement of the marker bed and its performance.

Jan 1, 1998

By Andrew I. Hustrulid

The discrete element method has successfully been used to model the behavior of material flow in transfer stations. With position, velocity, and applied forces for every particle and boundary in the simulation available at increments of 10-5 seconds, the next critical step is the presentation of this data in a concise and beneficial form. This paper discusses several methods of presenting the data from discrete element simulations that are used to improve the performance of a transfer station. These measurements are also used as a learning tool to better understand and visualize how material transfers from one belt to the next.

Jan 1, 1998

By Courtney A. Young

Cyanide is a fast-acting, highly toxic substance but, at the same time, is deemed essential for sustaining life as well 'as our standard of living. In this manuscript, the facts about cyanide are presented beginning with a brief history and definition and ending with a discussion on cyanide alternatives. Other topics include speciation, physical characteristics, toxicity, manufacturing, cyanogenics, cyanide cycle, separation, destruction, and markets including those outside the mining industry. Emphasis, of course, is placed on gold production by leaching and how it is influenced by ore type, mineral characteristics and economics as well as its advantages and disadvantages.

Jan 1, 1998

By G. L. Liu

"Deformation Banding ( DB ) in cold rolled mild steel has been experimentally established by microstructure investigation. Deformation banding model includes such deformation mode when it is applied to rolling texture simulation. The cause for the occurrence of deformation banding is the reduction of the total work for plastic deformation through a relaxation of the deformation constraints. In the first DB model, all grains are assumed to band from the first deformation step. Such an unrealistic assumption has been eliminated in the new model by the introduction of a banding criterion based on an energy minimizing approach. The prediction is closer to the measured texture by applying banding criterion and setting critical resolved shear stresses (CRSS) ratio for { 110 } and { 112 } slip modes to 0.85.IntroductionBased on the continuum theory of plastic flow and deformation mechanism of crystallographic dislocation slip, Taylor's FC ( Full Constrain ) theory [1] has been widely used in texture modeling. As the process of cold rolling of sheet materials produces a microstructure consisting of elongated or equiaxed flat grain or cell, the ""lath"" and ""pancake"" relaxed constraints ( RC ) models [2, 3] were introduced as the successful improvements over the classical FC model. It has been also recognized that crystals may split into different orientations during deformation and the term deformation banding is used to describe such deformation processes [4, 5]. Lee et al. [6, 7] pointed out that the success of the RC theory in predicting textures depends on the physical processes of deformation banding. They developed so called Deformation Banding ( DB ) model by considering DB in the longitudinal plane to be accounted for by the RC method and allowing DB in the rolling plane. DB model was applied to simulate the texture development in bee case [8], the predicted bee rolling textures are in reasonable agreement with the measured textures. In the first DB model, however, all grains are assumed to band right upon the first deformation step. A banding criterion was formulated [7] which states that DB will occur if the work used in DB model is less than that in RC model. Such criterion has been incorporated into the original DB model for texture simulation and is referred to as DBC ( Deformation Banding Criterion ) model."

Jan 1, 1998

By Glenn C. Miller

Cyanide is the most common lixiviant for extraction of precious metals, and its efficient use in open pit mines has contributed to the increase in world production of gold during the previous two decades. With this expansion of precious metals mining using cyanide, public concerns have developed in response to the inherent public perception of cyanide as a tox-in as well as a series of environmental problems that are directly or indirectly related to cyanide use in open pit mining. Some of these have technical or regulatory solutions, while others will require additional investigation before they can be resolved. The following discussion will summarize some of the public concerns regarding the use of cyanide in precious metals mining. The issue of cyanide use in large scale precious mining is controversial, and recent banning of cyanide use in open pit mines in Montana, or complete banning of cyanide in Hungary has reflected those international concerns. The underlying basis for some of the bans (e.g. Montana) reflect a general concern of the environmental impacts of mining, rather than specific issues related to risk of cyanide use. The human safety record for cyanide use, particularly in the developed countries is good, and cyanide is clearly the most efficient lixiviant for precious metals. Indeed, the relatively short lifetime for cyanide in the environment renders it one of the less problematic chemicals used for extraction of gold from ore. Mercury amalgamation or use of bromide as a lixiviant are certainly much more problematic. What, then, is the basis f~r the international concern about precious metals mines that use cyanide. Ifuse of cyanide for gold recovery is to continue, what additional infom1ation needs to be developed that will allow a better management of the risks of cyanide? Which of the concerns are directly related to cyanide, and which are indirect concerns that more related to effects of open pit mining. Under what conditions should use of cyanide be discouraged? DUl::ing June of 2000 the United Nations Environmental Program conducted a two-day workshop on cyanide use in mining that was attended by persons from the mining industry, regulators and environmental community. Support and attendance at this workshop reflected concerns by all three groups on further restrictions for cyanide use and the emerging potential for guidelines for better management of the catastrophic release of cyanide-containing mining waste. The following discussion is meant to focus-on those risks and explore the basis for an often negative reaction to precious metals mining using cyanide. It is presented in the format of a statement, followed by a discussion. While admittedly provocative, the statements are meant to express the concerns? of the public regarding cyanide and the mining industry.

Jan 1, 1998

By A J. MacDonald, M P. Raffield

The South Deep massive orebody consists of 20 to 30 m of payable conglomerates ranging in dip from 11¦ to 20¦ and at depths of between 2400 m and 3400 m. The mine design process selected a mining method with a proven record of application that could be adapted to overcome the inherent difficulties associated with the depth, thickness and structural influences of the South Deep orebody. A modified cut and fill mining method provides a concentrated and highly flexible method of extraction. An integrated destressing cut will enable the modification of the stress environment such that it is suitable for massive mining operations. The choice of backfill type and stoping width in the destressing cut ultimately determines the characteristics of the stress modification and, as such, is critical to the success of the cut and fill operation. This paper discusses the decision process undertaken to determine the optimum backfill type and stoping width combination in terms of, conditions in the destressing cut faces and in the massive mining environment. Numerical modelling has been extensively used to analyse various scenarios to aid in the decision process.

Jan 1, 1998

By Tim J. A. Smith

Fundicion Refimet S.A. has operated a custom copper smelter at La Negra, near Antofagasta in northern Chile since 1993. From an initial operation based on Reverb smelting and Peirce-Smith, converting, the plant was expanded from 90 000 t/y to 160 000 t/y copper production in early 1997, by conversion to oxy-fuel smelting and use of concentrate injection on Converters. As part of this expansion a novel reverb gas cooling and cleaning system was developed and designed by Kilborn SNC-Lavalin Europe, the London, UK-based mining and metals; Office of Canada's SNC-Lavalin group. The reverb gas cooler needed to satisfy several very specific requirements including low cost, flexibility, robustness and simplicity of operation. Of particular importance was the requirement to cool and clean the ,oxy-fuel reverb gases and render them suitable for subsequent treatment in a conventional sulphuric acid plant. It was also important to avoid accretion or dust handling problems. This paper describes the key design features and subsequent successful installation, commissioning and operation of the unit.

Jan 1, 1998

By Ron Bromenschenkel

The State of California, Department of Transportation is currently retrofitting a major interchange near the San Francisco area. The project is located in a highly traveled area of Oakland with light rail commuter service near many footings. Over 600 micropiles are being used in conjunction with CIDH piles for footing stabilization. A specially designed Soil Nail pile will support footings for a new light rail utility structure. Pile testing features in this contract serve as points of interest for future foundation designs. The presentation focuses on substructure issues of this incterchange retrofit. Both design and construction considerations will be covered. Design Considerations: ? Project Description ? Structure inadequacies ? Design criteria ? Design contraints ? Retrofit strategy ? Consultant analysis ? Pile Designs and Test Sites ? Contract Specifications ? Construction Plan and Cost

Jan 1, 1998

The old Trekelano mining area is situated in the Cloncurry Gold and Mineral Field 14 km east-south-east of Duchess. It connected with the main Cloncurry-Dajarra railway line by a private line from Juenburra, a distance of 10 km. The distance by rail from Townsville is 561 km. The area was first mentioned circa 1902 - 1903 when a very short report said, that a Tony Allis had taken a parcel of copper ore out of a mine which, he called æThe InheritedÆ. After that report, nothing further was printed until about 1906, when traces of copper were noticed on a wagon track going to Kiama Well. The Trekelano deposit did not outcrop, with the cap covered by about two metres of soil. The deposit was named after an early pastoral holding. The early prospectors were however disappointed by TrekelanoÆs low copper grades, approximately five per cent Cu. This is understandable when, in those days, about 25 per cent was the cut-off grade for mines in the district. Meanwhile, The Hampden Mining and Smelting Company were constructing a smelter to treat their sulphide ores at Kuradala that was replacing their high grade oxides ore. By about 1910, the Hampden Mining and Smelting Company was experiencing smelting problems, and needed suitable oxidised copper ore to blend with the Kuradala pyritic ore. Someone must have remembered the Trekelano low-grade oxides, resulting in agreement to mine and cart the ore to Duchess, from where it was railed to Hampden, as Kuradala was known at that time.

Jan 1, 1998

By G. T. Adel, P. E. Richardson, R. Pazhianur

Cathodic protection using impressed current was employed to reduce mill wall wear during ball milling. Wear rates were determined from weight-loss measurements made on four 1-in.-diam mild steel coupons that were installed flush with the interior surface of the mill wall. Grinding tests were conducted on quartz, pyrite and quartz-pyrite mixtures at pH levels of 4.6, 7.1 and 9.2. Cathodic protection was shown to reduce mill wear by 30% to 60%. An examination of the coupon surfaces using scanning electron microscopy showed that cathodic protection greatly reduced pitting corrosion. The presence of a sulfide mineral, such as pyrite, was found to increase the wear rate significantly, possibly due to galvanic interactions. It was also found that the wear rate is significantly higher than the sum of abrasive wear and the corrosive wear, due to a synergistic effect.

Jan 1, 1998

By M Grossi, G Baiden

This paper describes a new mine backfill method based on a newly invented binder with several years of test results from laboratory and onsite applications. The new binder has several advantages over traditional Portland and slag cement binders. One tonne of the new binder can replace two to three tonne of Portland cement when used to consolidate backfill and can result in the same compressive strength within seven days. When comparing backfill slurries of the same pulp density, the new binder attains more volume of in-place backfill mass than Portland cement because of the high crystallisation of water, resulting in tightly filled stopes. The crystallisation of the water provides for less or no dewatering in the backfill stope and easier transportation of the backfill slurry. Pastefill performance can be achieved by using pulp densities typical of a hydraulic backfill and the new binder, all the while transporting with the same ease of hydraulic fill.

Jan 1, 1998

By William J. Miles

The inhalation of dust has been a problem in the mining industry since antiquity. Crystalline silica is now known to be the cause of silicosis, a form of pneumoconiosis that is associated with excessive exposure to respirable particles in some mining and industrial environments. Crystalline silica was reviewed by the International Agency for Research on Cancer (IARC) in 1986 and classified as a Group 2A, Probably Carcinogenic to Humans in Volume 42 and Supplement 7 of the IARC Monographs (1987). In 1996, IARC reviewed additional literature and studies published in the intervening decade and recommended that quartz and cristobalite, two polymorphs of crystalline silica, be listed as Group 1, Carcinogenic to Humans. Their recommendations and reclassification were published in 1997 in IARC Monographs 68.[2] In both Monographs, IARC classified amorphous silicas as Group 3, Inadequate Evidence for Carcinogenicity to Humans.

Jan 1, 1998

By K. J. Shoop

Coal-fired power plants in the U. S. produce approximately 20 million metric tons of Hue-gas desulfurization sludge every year. The sludge mainly consists of calcium sulfite and calcium sulfate. This can be converted to synthetic gypsum, which in principle could be a marketable commodity. However, many Hue-gas scrubbers produce sludges that do not meet the quality requirements of the gypsum industry, and so their sludges must be landfilled as a waste. If a suitable method can be developed for removing certain objectionable impurities from the sludge, it will then be possible to market the material instead of landfilling it. A sludge from a natural-oxidation scrubber was characterized, and the main contaminant was found to be calcium carbonate from unreacted limestone. Based on the particle size and the characteristics of the material, froth flotation was considered as a method for purifying the material. Since no flotation studies have ever been carried out to separate calcium carbonate particles from calcium sulfite or calcium sulfate particles, it was first necessary to select a suitable collecting reagent. Based on Zeta-potential studies, the most suitable reagent was found to be an octadecylamine-octadecylguanidine complex. Results are presented for flotation of calcium carbonate from scrubber sludge using this reagent, in a reverse-flotation process. The best results were obtained when the sludge was first pre-cleaned using a water-only cyclone to remove unfloatable coarse limestone, followed by froth flotation to remove fine limestone.

Jan 1, 1998