Search Documents

By J. Lorosch

Improvement of current leaching technology was found necessary when processing ores which are more difficult to leach because they generate highly viscous, air-rejective pulps. Cyanidation of these pulps has to run at low oxygen concentrations if the conventional aeration technique with compressed air is used. Since the dissolution rate of precious metals mainly depends on the concentration of dissolved oxygen in the pulp [1, 4, 5], the kinetics of the gold extraction become slow in such cases, which in turn often leads to a significant decrease in the overall gold output within the conventional leaching time of up to 48 hours.

Jan 1, 1988

By G. A. Goller, Y. C. Lo

Microscale studies involving an ultrafast load cell have been shown to provide direct and accurate measurements of particle strength, particle fracture energy and particle breakage functions under different loading geometry conditions. The effect of grinding media size, shape, density and surface properties on the energy efficiency can be quantitatively determined for different materials to be ground. The applications of microscale comminution studies have been demonstrated to provide good predictions of grinding mill performance with different grinding media.

Jan 1, 1995

By Karen L. Menna

At Digital Equipment Corporation, increasing demands on executive secretaries to share, track, and retrieve information prompted development of ALL-IN-1 System for Executive Services. Executive secretaries asked engineers to combine word processing and electronic mail with utilities for managing time; logging and tracking telephone calls, letters, and inquires; creating presentations; compiling directories; and archiving. The system, two years in development, now automates the president's and senior vice presidents? offices at Digital. It allows secretaries to interrupt any task with two keystrokes, and return later to the original task. The system has speeded customer response, enabled online information sharing, and increased professionalism and customer satisfaction.

Jan 1, 1989

By David L. Gefvert

A general review of the role of cationic flotation reagents in the beneficiation of phosphate, iron, and potash ores. The three major types of cationic collectors-amines, ether amines, and condensates will be compared and contrasted. The effect of particle size, water chemistry, and water temperature on the choice of cationic flotation reagents for each industry will be discussed.

Jan 1, 1986

By J. Vaino Huhta

An exploration program which covered an area of about 17 000 km2(6564 sq miles), was carried out between 1966 and 1969 by the United Nations project named "Mineral Survey of the Azuero Area." The target became Cerro Petaquilla, Province of Colon, Panama. See Fig. 1. Regional exploration led to discoveries of many geochemical anomalies and minor mineralization, but it was only toward the end of the project that a promising target was indicated by a large zone of comer and molybdenum anomalies in stream sediments in a remote 1, area between the Cordillera and the Caribbean coast. Follow-up surveys established the presence of porphyry-type copper mineralization in the area now known as Cerro Petaquilla.

Jan 1, 1991

By L. D. Gehi, A. W. Khair, M. Ahmad

This paper presents an analysis of the effect of the dynamics of bit wear on dust generation. Two surveys have been conducted in order to assess the mechanism and type of bit wear and to evaluate the impact of bit wear on the productivity of the continuous miners. Used bits were collected from the underground coal mines and these used bits were utilized in laboratory coal cutting. The effect of bit wear on dust generation has been quantified and its impacted on dust generation and ventilation system has been exemplified.

Jan 1, 1993

By Robert Underwood, Boleslaw Tolwinski

In 1965 Helmut Lerchs and lngo Grossmann presented to the mining community an algorithm to find the optimum design for an open pit mine. In their words, "the objective is to design the contour of a pit so as to maximize the difference between total mine value of the ore extracted and the total extraction cost of of ore and waste." They modeled the problem in graph theoretic terms and showed that an optimal solution of the ultimate pit problem is equivalent to finding the maximum closure of their graph based model. In this paper. we explain how a dual simplex algorithm can be used to solve the same problem. We show how this algorithm is closely related to Lerchs and Grossmann's and how the steps in their algorithm can be viewed in mathematical programming terms. This analysis adds insight to the algorithm of Lerchs and Grossmann and shows how it can be simplified.

Jan 1, 1996

By R. L. Grayson

As a followup to a USBM-sponsored research project, the authors utilized the knowledge-base structure and system concepts from a Sun Sparcstation-based worker-scheduling system of the mine-management support system to develop a PC-based application. The new software adopts the nested-window concept to facilitate data collection and modification on personnel, including their availability and work priorities during a shift. The system can optimally allocate manpower on a work shift and can delineate supervisory training responsibilities. The various components of the software, including enhancements made to the original system, are described in detail.

Jan 1, 1997

By M. M. Ragin, B. J. Scheiner

The US Bureau of Mines (USBM) has been investigating the use of polyethylene oxide (PEO) as a flocculant for a variety of mineral wastes. As part of this investigation, the hydrodynamics of the flocculation process were studied. It was determined that to obtain optimum dewatering results, the factors of energy input into the stirrer, polymer concentration, and polymer dosage must be considered. It was found that at a given polymer concentration, there were an optimum stirrer speed and polymer dosage. With excess PEO, the amount of water removed in the trommel decreased, but no evidence for steric stabilization was observed.

Jan 1, 1987

By Roshan B. Bhappu, Sukhendu L. Barua

The economics of developing and operating small precious metal mines are unique and require much more scrutiny than larger mines since a limited tonnage must carry a heavy burden of capital investment as well as operating cost per unit ton to be mined and processed. Moreover, potential operators of small mines do not have the required expertise available to critically evaluate the technical and economic aspects of their projects. In this paper, the authors have attempted to provide technical and economic guidelines for developing and operating small precious metal mines. Capital and operating cost estimates as well as return on investment are provided for various scenarios utilizing different mining and processing techniques.

Jan 1, 1987

By O Gutsche, Fuerstenau D. W., R. Ravikumar

Six minerals and one ore, namely, barite, dolomite, galena, limestone, quartz, quartzite and taconite, were ground in single-particle comminution mode in a rigidly mounted roll mill with different levels of energy input. Grindabilities were determined from the median size of the self-preserving product size distributions, which was taken as a measure of the fineness of the ground material in an empirical energy-reduction ratio relationship. These values reflect the inherent resistance of the solids to mechanical size reduction that are least distorted by particle-particle interference effects, grinding characteristics, energy efficiency of the milling system employed and the extent of the fineness specified.

Jan 1, 1992

By Allen V. Reicks

Modern conveyor pulleys are welded steel structures subjected to dynamic loads. In this paper, fatigue notch and fracture mechanics methods are applied to several weld joints on typical pulley constructions. These methods are used to analyze field applications and are correlated with laboratory testing. Generalized approaches are presented which provide high confidence in pulley design with corresponding high reliability.

Jan 1, 1996

By Harold D. Taylor

Lognormal grade distributions are definitely the rule rather than the, exception in many types of deposits, including precious metals, uranium, and many others. The "normal theory" geostatistical techniques do not work well in these situations because the occasional high grade values, perhaps several orders of magnitude larger than the median, can overwhelm the rest of the data, resulting in variograms and Kriged estimates which are unrealistic or even ridiculous. Robust techniques for variogram modeling have been proposed, and truncation of high sample values can produce more reasonable Kriged estimates, but the technique of working with log transformed data appears to be the best method of handling lognormal data. This paper will discuss primarily the two parameter lognormal case, with some discussion of the three parameter lognormal, but no discussion of other methods of transforming data, such as disjunctive Kriging.

Jan 1, 1982

By J. C. Yingling, R. Kumar, J. Sottile

The capability for on-line measurement of the quality characteristics of conveyed coal now enables mine operators to take advantage of the inherent heterogeneity of those streams and split them into wash and no-wash stocks. Relative to processing the entire stream, this reduces the amount of coal that must be washed at the mine and, thereby reducing processing costs, recovery losses and refuse-genera¬tion levels. In this paper, new ap¬proaches for optimal control of the segregation process using time-se¬ries models and empirical distribu¬tions are presented and demon¬strated using field data.

Jan 1, 2000

By D. J. Cook, R. H. Fan, D. R. Maneval, Y-H. Shen

In this study, two placer mine processing plant effluent waters of significantly different characteristics were tested to determine the applicability of polymers along with other techniques to achieve reduced levels of turbidity. The waters from a Gilmore Creek mine and a Crooked Creek mine were characterized both as to their chemical and physical properties. The inorganic minerals were in large measure identified, and the principal cations were identified. The fine solids were studied as m their mineral identification and the extent of their electrical charges. Test work was done using polyrthylene oxide (PEO) and a liquid cationic polymer along with adjunct additives to determine optimum amounts of these coagulants for minimum consumption and optimum settling efficiency.

Jan 1, 1990

By Fernando Muge

A complex pyrite orebody located in the South of Portugal (MO INHO) was exploited in the past by cut and fill methods until a certain level. It was decided to design a new plant for non ferrous metal extraction and the rate of production and exploitation method was modified accordingly. So, a sub level stoping (SLS) method was en visaged for the exploitation of the deepest part of the orebody (under 265 m level). For the planning of this SLS method, it was decided to perform a geostatistical study of the orebody, on the basis of the available information, which consists mainly of channel samples assayed for Cu, S, Zn and Pb.

Jan 1, 1979

By Paul M. Godlewski, Gerry Millar, Harvey W. Parker

Recently, over 70 railroad tunnels in the western USA have been enlarged and rehabilitated "live track," utilizing modern excavation and lining methods, in most cases to clear the larger double-stack container cars. This paper presents the general conditions of the tunnels and the technical aspects and costs of the rehabilitation of approximately 40 kilometers of tunnels, which range in length from a few hundred meters to 13 kilometers. Concrete-lined tunnels were rehabilitated by grouting and rock bolting, while unlined or timber-supported tunnels were relined with shotcrete and rock bolts. High output lining methods were required because of limited track time. Enlargement has been accomplished primarily by carving notches out of the concrete linings with a roadheader, or occasionally with saws. Unlined tunnels were enlarged by drill-and-blast or roadheader excavation.

Jan 1, 1991

By J. Stachurski, N. A. Abdel-Khalek

The objective of this investigation was to compare the results of countercurrent, column cell flotation vs. conventional (mechanical) cell flotation for the cleaning of a sulfur ore (-0.5 mm, 27.43% S) and its discrete size fractions. The tests were carried out using diesel oil as a collector and alcohol as a frother. Generally, column flotation produced concentrates of higher grade. For example, column cell flotation produced a nonwashed concentrate of 65.3% S with a recovery of 84.1%. However, conventional cell flotation produced a rougher concentrate of lower grade (57.0% S) and higher recovery (92.5%). At a superficial-wash water velocity of 0.265 cm/sec, the column product grade increased to 76.4% S, with a slightly lower recovery (80.3%). However, a concentrate with a similar recovery but a lower grade (74% S) than that of the washed product was obtained after three cleaning stages with the conventional cell. The column gave superior results for the flotation of fine and ultrafine particles.

Jan 1, 1994

By A. L. DeVegt, H. G. Bayer, C. J. Buisman

During the last ten years, Paques Inc. has been engaged in the development and installation of treatment systems to remove sulfur compounds from water and gaseous streams using biotechnological processes. Metal and sulfate can be removed from mine waters in two biological steps. In the first step, sulfate-reducing bacteria converts sulfate to hydrogen sulfide (H2S). The HS reacts with the dissolved metals to form insoluble metal sulfide precipitates. In the second step, sulfide-oxidizing bacteria convert excess H2S to elemental sulfur. The Budelco Zinc Refinery in The Netherlands installed a groundwater treatment system to remove metals and sulfate using the biological steps described above. The system has been operating since May 1992 and has been treating 5,000 m3/d (180 thousand cu ft/day). A pilot plant began operation in November 1995 at Kennecott's Bingham Canyon Utah copper mine to develop processes for metal and sulfate removal from groundwater and for the selective copper recovery from leach water. The principle of the biotechnological methods, the full-scale experience and an overview of the test program at the mine are presented

Jan 1, 1999

By Ian Longson, Darron W. Dixon

This paper describes the results of an investigation into the application of a statistical method for the prediction of general air-body methane concentration in longwall coal districts. An important and necessary part of the research was the acquisition of representative monitored mine environmental and coal production data. The monitored data was used to build time series models of general air body methane concentration, air velocity, barometric pressure, coal production and methane drainage variables of differing timescales according to the Box-Jenkins method of time series analysis. The univariate models were used to identify causal relationships between methane concentration and its explanatory variables. Coal production was found to be the dominant variable in the determination of the quantity of methane emitted and where appropriate, multivariate time series models were built in which expressions for methane concentration in terms of coal production were obtained. Finally, forecasts of methane concentration values were generated from the multivariate models to determine their forecasting capabilities.

Jan 1, 1993