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By R. B. Inturi, R. G. Reddy

Solid-state reduction of roast Movat chromite ore with carbon was carried out as a function of the C/FeO ratio at temperatures ranging from 800°C to 900°C. The reduction was studied using thermogravimetric analysis (TGA). A two¬stage mechanism consisting of the reduction of FeO with carbon monoxide and the regeneration of CO by the oxida¬tion of carbon with CO2 was proposed. The rate-controlling step is the carbon oxidation reaction. A kinetic equation, that of random nucleation, was proposed. The activation energy for the reduction was determined to be 55,800 J/mole and is compared to those activation energies determined for other chromite ores.

Jan 1, 2000

By J. R. England, W. J. Taylor

The Sudbury Basin is the scene of the mining operations of the Ontario Division of the International Nickel Company of Canada, Limited. Around the rim of the geological formation and within thirty miles of the City of Sudbury are located twelve operating mines and one open pit operated by the Company. The City, with a metropolitan population of some 100,000 lies 240 miles Northwest of Toronto. In addition, there is one mine in Northwestern Ontario, at Shebandowan, 700 miles Northwest of Sudbury. In 1973 these mines produced 16.5 million short tons of ore of which 14.9 million tons were from underground and the balance from open pit operations. Mining methods include blasthole, sublevel caving, induced caving, shrinkage, cut-and-fill and undercut-and-fill. Raise boring commenced at Inco in 1964 and is now applied at all mines in the Sudbury District (Figure 1). [ ]

Jan 1, 1974

By Don U. Deere

The tunnel boring machine (TBM) can be a magnificent tunneling device under optimal rock conditions. Such ideal conditions would include good Rock Material Characteristics (compact, uniform; low to medium strength, hardness, and abrasiveness); good Rock Mass Characteristics (few joints and shears; unweathered); and good Geologic Environmental Characteristics (above groundwater level and moderate in-situ stress). Such idealized rock conditions would eliminate support problems, fallout at face and grippers, frequent cutter changes, and water problems. Daily advance rates of 50 m would be commonplace. Unfortunately, nature seldom provides the ideal geologic characteristics. The challenge to the geologist, machine manufacturer, and contractor is to provide equipment and procedures to best handle the adverse geologic features, once identified.

Jan 1, 1981

By Wm. Randolph Reed, John A. Organiscak

Haul trucks have the potential to generate large amounts of respirable dust. This respirable dust has been shown to be a health hazard to personnel, especially if it contains a high silica content. Lack of dust sampling data from haul trucks prompted the completion of a study to quantify respirable dust concentrations. These field studies were conducted measuring instantaneous respirable dust at stationary locations from passing haul trucks at a stone quarry and a coal mine site. Fugitive dust levels from haul trucks were analyzed to characterize dust dispersion. This analysis will indicate safe following distances for haul trucks and other heavy equipment to avoid over-exposure of respirable dust from the lead haul truck.

Jan 1, 2005

By Thomas E. McNider

On July 20, 1990, a Spontaneous Combustion Control Plan was approved by MSHA for Jim Walter Resources, Inc. No. 5 Mine. The mine operated under the plan for twenty-nine shifts before MSHA revoked the plan. A total of fifty-five seals were constructed during the process of implementing the plan. The major difficulty in applying the control concept resulted from problems controlling leakage at the numerous seals. The number of seals was a direct consequence of attempting to merge the traditional bleeder system, used in all the Blue Creek Mines, with the bleederless system Jim Walter Resources proposed as a means of controlling the spontaneous combustion hazard. This paper discusses Jim Walter Resources experience with spontaneous combustion control and the new safety standard which applies to underground coal mines that demonstrate a history of spontaneous combustion and how this standard would apply to our No. 5 Mine. The new Ventilation Standards were published in the Federal Register on May 15, 1992, and scheduled to go into effect August 16, 1992.

Jan 1, 1993

By Elza F. Burch

Feeding 600 pm X 0 raw coal to heavy media cyclones, along with the +600 pm size coal, produces an efficient separation of both the +600 pm and 600 pm X 150 pm sizes. Major advantages of the process include the elimination of desliming screens and secondary fines circuitry for cleaning the 600 pm X 150 pm size coal, and result in a very simple circuit. Incorporating four 660 mm diameter heavy media cyclones, the Providence Plant of Island Creek Corporation has operated efficiently for ten years with a magnetite consumption rate of less than 0.45 kg per ton of raw feed at a feed rate of 454 tph.

Jan 1, 1988

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 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 Peter Keppler, Stephen D. Bundy

"Due diligence" is a review or audit of a facility or business to assess and quantify risks and operating status before an acquisition. Due diligence findings can be used to negotiate the price, general terms, and indemnification provisions in the purchase and sales agreement. In addition to assessing out- standing liabilities, necessary capital improvements, and the adequacy of operating budgets, due diligence should include "nontechnical" considerations, such as local community acceptance and relations, and the effect on the company's public image and operations. This paper will discuss how these considerations can be addressed in the due diligence process and factored into the transaction. Also, innovative means for risk reduction and risk transfer, during and after the transaction, will be discussed.

Jan 1, 2001

By Wen-Long Cai, A. Frederick Banfield

This paper investigates, through case studies on a porphyry copper and a coal deposit, the differences and relevances between an approximate production schedule approach, i.e., the best case and the worst case schedules and a practical production schedule approach. The comparisons were with regards to: 1) choosing an optimum ultimate pit size, 2) determining processing capacities, 3) selecting 'optimum' cutoff grades, and 4) blending. The comparison criteria was to maximize the project net present value. Conclusions were drawn based on the study results.

Jan 1, 1996

By Robert C. Bates

Published information on costs of radon-daughter control in uranium mines was analyzed to develop estimates of the cost per ton for any level of radiation exposure control. All data were converted to 1967 cost of living index to provide a common analysis base. Results of the analysis show that the cost per ton increases exponentially as the radiation level is lowered. A linear relationship with the cost of living index is assumed, and equations and graphs are provided to estimate control cost per ton for any exposure control level and cost of living index.

Jan 1, 1981

By S. Bhattacharya, M. M. Singh

The Surface Mining Control and Reclamation Act of 1977 (SMCRA) requires under-ground coal mine operations to prevent "material damage" to renewable resource lands caused by subsidence. However, what constitutes material damage is not defined. This paper discusses the applicable criteria for agricultural lands, forests and grazing lands, surface water bodies, and ground water aquifers. Although data on the subject are limited, an attempt is made to present quantitative guidelines to distinguish between moderate and severe damage due to subsidence.

Jan 1, 1988

The importance of factoring mining dilution into the estimation of ore reserves in an open pit mine is discussed. An example that relates the issue of mining dilution to the size of the smallest volumes that can be mined selectively is given. The relationship between the size of the selective mining units (SMUs) and the variance of their average grade is presented. The concept of variance reduction and its use in factoring mining dilution into geostatistical ore reserve estimation is described. An approach to estimate a variance reduction factor by way of conditional simulation is introduced.

Jan 1, 1998

By Adam Feiler, John Ralston

Optical reflectometry was used to study the attachment and subsequent detachment of silica particles (diameter 25 nm) from the surface of titanium dioxide wafers under well-defined hydro- dynamic conditions. Atomic force microscopy was used to measure the interaction between silica spheres (diameter 7 pm) and titanium dioxide wafers under the same solution conditions. In addition to repulsive electrical double layer forces, adsorbed polyphosphates provide a short-ranged steric layer that reduces the lateral interaction between the surfaces. The use of these two complementary techniques has given valuable insight into the process responsible for fine particle detachment and has particular application to surface cleaning.

Jan 1, 2003

By Y. Lin

The objectives of this investigation were to study the zeta potential characteristics of a Powder River Basin coal in water and to study the effects of zeta potential on the agglomeration of coal particles. The electrokinetic measurements show that the zeta potential of the coal is dependent on pH, temperature, coal concentration and contact time with water. The effects of various additives for changing the zeta potential of the coal were also evaluated. It was found that the strength of the coal agglomerates is increased when the zeta potential diminishes. Neutralizing the zeta potential enhances agglomeration. Therefore, it is important to control the zeta potential of coal to achieve optimum performance in coal-particle agglomeration.

Jan 1, 1997

By R. J. Manser

A mathematical model of a shaking table is being developed, for inclusion in a package for the simulation of gravity concentration. The general form of the modules and how they fit into the package is briefly described. The separation on a shaking table is controlled by a number of operating variables and the importance of these variables in the model development is discussed. The influence of wash water, feed pulp density, deck slope, deck amplitude and mass feed rate are reported. The form of the model is described being based on the probability of a particle of defined size and density reporting to a specific discharge site. The mathematical relationships which relate size and density distributions to variations in the operating parameters are presented. The use of these functions in the prediction of the performance of a shaking table is outlined.

Jan 1, 1986

By David Jenkins

Grefco Inc. operates two diatomite mines in the western Santa Ynez Mountains. The larger of the two mines, the Palos Colorados Mine, is located approximately seven miles southeast of Lompoc. The Miguelito Mine is located about two miles south of Lompoc on the west side of the Miguelito Canyon. Diatomite from the Palos Colorados and Miguelito mines is trucked to the Grefco plant at Lompoc for processing (Figure 1). HISTORY Grefco, Inc. evolved from the originating Dicalite Company which in 1929 began operations at the Walteria plant in the Palos Verdes Hills south of Los Angeles. In 1942 Dicalite leased the Palos Colorados mine at Lompoc. In 1944 the Dicalite Company was purchased by Great Lakes Carbon Corporation.

Jan 1, 1995

By Park. D. W., Y. M. Jiang, L. A. Morley, W. Keeton

Underground room-and-pillar mining operations in the Warrior Coal Field in Alabama frequently suffer instability due to soft floors and thinly-laminated immediate roofs. This investigation concerns a mine that was experiencing ground-control problems with weak floor conditions. Several roof falls occurred locally, and as much as 0.6 m (2 ft) of floor heaves have been experienced. The paper presents the results of comprehensive analyses conducted on floor heave, roof sagging, pillar- penetration and floor bearing capacity using instrumentation and numerical modeling.

Jan 1, 1993

By Y. H. Chia, P. Somasundaran

Carrier flotation of anatase from clay using coarse calcite is investigated, together with relevant basic properties of the system including aggregation and zeta potential, under different chemical and hydrodynamic conditions The roles of carrier sue and amount also are considered Mechanisms responsible for selective aggregation and flotation are reviewed

Jan 1, 1983

By J. J. Schwoebel

Resource Enterprises Inc. (REI) is exploiting the coalbed gas resource by working in unison with active underground mining operations. At REZ7s pilot project at the Soldier Canyon mine, Carbon County, UT, RE1 has drilled nearly 15.25 km (50,000 ft) of horizontal in-seam and slant boreholes during the initial two years of drilling activity. Produced gas has been sold to a natural gas transmission company on a continuous basis since mid 1983.

Jan 1, 1988