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By S. S. Peng

An expert team consisting of geology, civil, and mining engineer professors was organized to investigate several problems of longwall mining in three mine sites including: site investigation, panel layout and support selection, overburden strata movement, surface subsidence and structural damages, slope, stability, well and stream dewatering, etc. The results include the development of a PC software package such as powered support selection, Surface subsidence prediction, optimum panel dimension, and pillar design.

Jan 1, 1989

By B. Ainsworth

The 1972 discovery of the Howards Pass lead-zinc deposit was the product of systematic regional geochemical surveys used to evaluate conceptual geological models for the metal-rich black shales of the Selwyn Basin. Motivation of personnel involved in all aspects of work was as critical a factor to the success as the existing corporate attitudes and infrastructure. Exploration programs were flexible but maintained a focus only on targets of sufficient economic potential to support operations in remote locations. Direct costs for the programs that lead to the discovery were in the order of $500,000 (Canadian 1972). Geological reserves today stand at over 500 Mt (511 million st) of 7% combined lead-zinc, containing a higher grade zone of nearly 10 Mt (11 million st) of 16% combined lead-zinc.

Jan 1, 1991

By David R. Quigley, Patrick R. Dugan

First reports of microbial coal solubilization appeared in the early 1980's (Fakoussa, 1981; Fakoussa and Truper, 1983; Cohen and Gabriele, 1982). These degradations, which occurred at ambient temperature and pressure, resulted in a dark brown to black viscous liquid and required days to weeks to occur. Rates and degrees of coal biodegradation varied from coal to coal. Hard coals were not extensively degraded (5-7%) while low-rank coals such as Leonardite, a sublignite, were completely solubilized. A correlation between degree of weathering or oxidation of coal and the coals susceptibility to biological attack was observed. This led to oxidative pretreatments as a method to enhance microbial degradation of coal (Strandberg and Lewis, 1986). Products of microbial degradation of coal are water soluble solids that do not have significant solubilities in organic solvents (Wilson, et. al., 1987; Quigley, et. al., 1987; Quigley, et. al., 1988a). Solutions of solubilized coal did not separate or form precipitates which suggested that they were true solutions and not colloidal suspensions. Biosolubilized coal contained more oxygen than starting material suggesting that microbial attack of coals involved oxidative cleavage of carbon-carbon bonds. This small change in oxygen content was the only change observed in coal structure during the biosolubilization process. Many coal solubilizing microorganisms have been isolated. Some are lignin degrading organisms such as Phanerochaete chrysosporium and various Streptomyces species (Gupta, et. al., 1988; Wilson, et. al., 1987). This was not unexpected since the structures of lignin and low-rank coals are similar. These organisms produce an enzyme complex, ligninase, that utilizes hydrogen peroxide to oxidatively cleave the bond between a and ß carbons of an aliphatic chain bound to an aromatic nucleus. Another important organism is Trametes versacolor (syn. Coriolus versacolor, Polyporus versacolor). Even though this organism produces a ligninase (Dodson, et.al., 1987), coal solubilization has been attributed to the enzyme laccase (Pyne, et. al., 1987). Laccase utilizes molecular oxygen to oxidatively cleave a - ß bonds using a mechanism similar to that observed for ligninases (Kawai, et. al., 1988). Other coal solubilizing microorganisms have been isolated from coal outcrops (Ward, 1985; Ward, 1988), but enzyme activities responsible for coal solubilization have not been identified. Research at the Idaho National Engineering Laboratory has focused on those mechanisms involved in coal biosolubilization. An

Jan 1, 1989

By Christopher P. White, John R. Wagner

This paper will discuss the complex and difficult soil conditions encountered in the sinking of 15 shafts of 18m to 27m depth and the excavation and lining of 6700m of 2.74m dia. interceptor sewer on Staten Island, New York. The complex soil profile consists of dense glacial till and sand outwash strata overlying the much older cretaceous sand, silt and clay strata. The tunnel varies from 8m to 14m below the nearby sea level. A significant amount of boulders were anticipated in the till. therefore, a decision was made to excavate the tunnel with a digger shield installing bolted, gasketed concrete segments. The bid documents stated the soils were dewaterable. Several conditions occured in this complex soils matrix which required modifying the planned means and methods including the necessity to use compressed air. The conditions encountered and the equipment used will be described.

Jan 1, 1991

By Anthony R. Przybylek, John M. Visnesky

INTRODUCTION Thermal dryers have been utilized for reducing moisture of bituminous coal since the late 1930's. Since that time, numerous changes in the coal industry have motivated advances in thermal drying technology. The purpose of this paper is to discuss the changes that occurred to dryer design and focus on current practices of fine coal drying. The major topics discussed in this paper are: - Early Thermal Dryer Design and Evolution - Current Drying System Design and Associated Components - Current Economics of Fine Coal Thermal Drying - Future Markets and Design Considerations EARLY THERMAL DRYER DESIGN AND EVOLUTION Background The practice of drying fine coal with heated air has been performed for more than one half century. Throughout that period, both Metallurgical and Steam coal producers have used this method for reducing the surf ace moisture content of their fine plant products. During the late 1930's and early 19401s, vibrating bed and flash dryers were used to per- form the drying duties. Closed water circuits and vacuum filtration had not yet been integrated into process circuitry and centrifugal dryers were in their early stages of development. During that same period, changes in mining practices were reshaping the distribution of coal to our processing facilities. Plants originally designed for the purpose of processing coarser fractions of coal were being burdened with additional quantities of fine coal. Those plants, unable to recover fine coal, would reject these solids to plant bleed. The higher incidences of stream pollution that resulted from these events prompted clean stream legislation and the need for new, more efficient fine coal recovery circuits. The coal processing industry responded to these needs by integrating closed water circuits and filtration into circuits. The fine coal filter cakes recovered exhibited poor handling characteristics by themselves and often required further dewatering to improve their characteristics. Flash dryers at that time were being used to dry the coarser products. For those facilities operating flash dryers, the solution to this new problem appeared to be simple. The filter cake was combined with the coarser (-1/4") coal and then introduced to the flash drying column for drying. The filter cakes, however, presented significant problems for the flash drying systems. Heavy lumps of filter cake could not be dispersed and conveyed by the rising hot air and as a result would settle out in the bottom of the column. This material, known as "drop-out", would then accumulate and require further handling. The solution to this problem was not an easy one. Sophisticated mixing equipment was employed to condition the feed to the dryers. As attempts to minimize drop-out with this approach failed, the only recourse was to collect the material with conveying systems and recycle it back to the plant or dispose of it. The additional costs of handling this material reduced the attractiveness of the flash systems and opened the door for the development of a new, more cost effective coal drying system. Due to the nature of the problems experienced by the flash systems, fluid bed systems were considered. Fluid bed dryers were being used in other industries at that time but had no operating history in the coal industry. Dorr-Oliver transferred technology from other industries and built the first fluid bed drying system for fine coal.

Jan 1, 1988

By K. A. Lapakko, D. A. Antonson

Fourteen samples of pyrite-bearing Archean greenstone rock (d < 6.35 mm, 0.04% < St < 1.22%) were characterized (particle size, chemistry, mineralogy) and subjected to laboratory dissolution testing. The only sulfide and carbonate minerals identified were pyrite and siderite, respectively. Quartz, chlorite and sericite typically comprised 90 to 98 percent of the mineral content. For the first 60 weeks, seven samples with sulfur contents less than or equal to 0.16% produced drainage pH values exceeding 6.0. Over this period, six of the seven samples with sulfur contents greater than or equal to 0.20% produced drainage pH below 6.0, with minimum values ranging from 3.2 to 4.7. The seventh sample (0.72% S) had a siderite content of 18%. Small amounts of magnesium and, to a lesser degree, calcium carbonates present in the siderite apparently dissolved to neutralize acid and maintain drainage pH above 6.0. Sulfate release rates generally increased as sulfur content increased, and the rates of pyrite oxidation estimated for individual samples were roughly half to five times that reported in the literature for the abiotic oxidation of pyrite by oxygen. Observed neutralization potentials ranged from 0.2 to 2.0 g CaCO3/g rock.

Jan 1, 2002

By F. Milton Lewis

In 1977 a paper was presented which reviewed the cost trends in producing copper by conventional processes for five years, 1972 through 1976. In this paper these costs have been updated to include the years 1977 and 1978.

Jan 1, 1979

By Isabel Barton

This article describes and analyzes the history of research into the origins of the uranium-vanadium(-radium) deposits of the Paradox Basin. For several decades after their discovery in 1881, research was desultory and almost entirely descriptive, fluctuating with demand for vanadium and radium. Systematic geologic descriptions, accumulated between 1910 and 1950, supported rapid progress during a government-backed surge of research in the 1950s, when uranium was the chief commodity of interest. Most of the major theoretical innovations date from this decade, including the use of concepts from solution chemistry to identify the conditions and constrain the processes of deposit formation and alteration. Research from this time was highly influential in geology at large, providing the model for sandstone-hosted uranium deposits worldwide and numerous new minerals and mineral structures. After about 1960, mine production remained high but research dwindled, and most new advances were to the details of the hydrothermal model of ore formation rather than its core concepts. By the end of the 1960s, the deposits were understood to have formed at the mixing interface of an oxidized, metal-bearing water with a reducing fluid of debated origin. Research was desultory over the ensuing decades; the source of the metals and the nature of the chemicals constituting the trap were not clearly established. They remain questions today, as do factors like the relationship between ore mineralization and the geologic history of the basin. (More in the full paper.)

Jan 1, 2025

By J. M. Keane, C. K. Chase

Critical to successful dump and heap leaching of copper is an adequate evaluation of applicable parameters. This paper deals with methods to establish optimum conditions for dump and heap leaching copper so that commercial operations can proceed. Discussion is also offered of ore occurrences and preparations for dump or heap leaching.

Jan 1, 1988

By K. E. Hjelmstad

Solution mining operations often encounter difficulty maintaining adequate leach solution flow into the ore formation because of loss of formation permeability near the injection well. Permeability loss caused by swelling and breakup of clays and fine particle migration can often be the cause of the problem. Combined permeability and leaching tests were done in the laboratory on samples of clay bearing ores to evaluate a clay-stabilizing polymer&apos;s effectiveness in preventing the problem. Test results indicate that treating the ores with cationic polymers could maintain permeabilities two to five times greater than the long-term permeabilities present in untreated ores. Both alkaline (pH 8.5) and acidic (pH 2.0) leaches were used in the permeability leaching tests. To determine the reasons for the success of the clay stabilizing polymer, clay swelling tests and zeta potential measurements were made on untreated ore samples and on ore samples treated with the cationic polymer. Test results indicate the cationic polymer could reduce the degree of negative charge on fine particles and their tendency to disperse, as well as reduce clay swelling. Test results indicate a potentially beneficial effect on operating parameters such as capacity and injection pressure during leaching, if clays and fines are kept stabilized. This may be done by treating the zone of high fluid velocity near injection wells with cationic polymers.

Jan 1, 1991

By X. Shi, F. -Y. Wang

Automation and robotics are the keys to new intelligent autonomous mining systems that can remove operators from hazardous and stressful mining environments and provide the tools for greater productivity. This paper presents the components necessary for an Intelligent Task Control System (ITCS) for machine control in dynamic unstructured mining environments. In particular, the design details of a controller for an automated excavator are developed. The excavator controller uses fuzzy logic to interpret forces and torques gathered from a wrist mounted force/ torque sensor during the excavation process. This approach enables the transfer of human heuristics and expert knowledge to the controller. Several excavation tests using the fuzzy logic controller are described. These experimental results represent the first step toward an integrated approach that uses force/torque, vision and other sensor data to perform generic tasks in uncertain mining environments.

Jan 1, 1995

By A. I. A. Salama

A computationally efficient technique for generating a balanced set of density or size separation data is developed. The technique proposed utilized minimization of a modified form of error squares to generate the optimum estimates of outputs mass yields (splits) and balanced direct mass distributions of feed and outputs. The estimated separation data set satisfies mass balance conditions of the streams mass distributions around the separator. The technique proposed avoids the generation of small negative values for the estimated feed and outputs direct mass distributions. Actual data are used to demonstrate the technique proposed.

Jan 1, 1996

By Donald C. Moore

Asamera Minerals Cannan Mine has been producing a 170 g gold/tonne (5 oz gold/ton) siliciaus flotation concentrate since July 1985. Flotation concentrate is shipped to a smelter for gold recovery. Numerous processes have been investigated to economically produce bullion on site. This paper describes the laboratory and pilot plant test results of a bacterial assisted oxidation of the refractory minerals. Economic comparisons with autoclaving and roasting processes are included.

Jan 1, 1989

By F. Romero, L. Yacher, M. Orchard

Specific software tools for Statistical Multivariate Analysis combined with real time process data were applied to Concentrator Plant at Compañía Minera Doña Inés de Collahuasi SCM in Chile, basically to two Mill Lines, each one with one SAG mill (32’x15’8MW)and one Ball mill (22’x36’9.7MW). The main objective was to empower the operator actions using process patterns references instead of process variable set-points. Pattern clustering and the analysis of pattern deviations regarding normal or desired pattern, allows for improvements in process control and the further implementation of soft sensors for those variables not included in the initial model.

Jan 1, 2003

By S. Fawell, H. R. Manouchehri

The main electrophysical properties, i.e., dielectric constant and electrical conductivity, of pure calcite, quartz and wollastonite mineral samples were measured and their triboelectric charge attributes were investigated by contacting minerals particles with different tribochargers made from different materials. In addition the energetic work function values for mineral samples were estimated due to their acquisition charge. Besides, the behaviour of triboelectrically charged of different particle size fractions of mineral samples were inferred. Finally an attempt were made to translate the findings from single mineral systems to a real carbonate ore. The results exposed good prospects to beneficate the examined minerals by triboelectric separation.

Jan 1, 2002

By M. Dale Slade, Gordon S. Bird, Robert S. Kelly

Gallium scrap is obtained from many different sources, therefore each lot received has to be evaluated and then processed accordingly. Some of the problem areas are separating small amounts of gallium from large concentrations of iron, eliminating trace amounts of gold, silver, copper, germanium, tin, and zinc from gallium, and having the flexibility to process each lot of scrap individually Following gallium from the raw scrap material to the final seven nines pure product requires stringent quality control and excellent analytical capabilities.

Jan 1, 1983

By Alan C. Noble

Ore reserve estimation is a multi- disciplinary process involving not only tonnage and grade estimation (resource estimation), but also consideration of technical and legal aspects such as mining the deposit, beneficiating the ores, and selling the product. This paper provides a background to under- standing resource estimation including geologic modelling, manual estimation methods, conventional computer methods. and geostatistical methods. Mine planning, metallurgical studies, legal/environmental, and marketing considerations are also discussed as they relate to estimating ore reserves.

Jan 1, 1991

By J. V. Byrnark, R. W. von Bitter

The Hibbing Taconite Co. concentrator flowsheet, which is noted for its simplicity, uses single- stage autogenous grinding coupled with two stages of magnetic separation and two stages of size classification to produce a magnetite concentrate. This paper discusses the pilot-plant development of single-stage grinding, the commercial mill grinding performance, and mill liner development. Process innovation discussion includes process control computer implementation, size classification improvements, mill speed changes, magnetic separator improvements, and quality control innovations.

Jan 1, 1987

By A. G. Provost

On April 3, 1981, Harrison Western Corporation was awarded a contract by Amax Alloy - A Division of Amax Inc., to sink the Henderson #5 ventilation shaft. The project was located on the Henderson Mine site 88 kilometers west of Denver near the town of Empire, Colorado (Figure I). The Henderson No. 5 Shaft, located in an Alpine environment at an elevation of 3145 meters, was a 9.8 meter diameter concrete lined shaft with a total depth of 793 meters. Work started and continued with Harrison Western employees until January 15, 1982. At that time, Amax made the decision to continue the shaft-sinking with their own labor, and with Harrison Western providing supervision under a management service contract. Shaft sinking continued under this arrangement to October 1, 1982, at which time Amax put the Henderson No. 5 project on standby status until further notice.

Jan 1, 1986

By Fred Heivilin

A symposium on the characterization and toxicology of mineral dusts was held Sept. 19 and20 in Washington, D.C. The symposium was held to update the minerals industry, the health community, government agencies and academia on the technical, health and regulatory aspects of minerals to be evaluated by the International Agency for Research on Cancer (IARC).In October 1996, the IARC met in Lyon, France, to discuss and prepare “Volume 68 of the IARC Mono-graphs on the Evaluation of Carcinogenic Risks to Humans on Silica, Silicates, Dusts and Organic Fibers.”

Jan 1, 1996