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By D. W. Fuerstenau, J. Vazquez-Favela

This paper shows how the efficiencies of size-reduction processes depend on the mode of particle constraint and energy transfer within the comminution device: namely, whether the process consists of single-particle loading, confined-particle-bed comminution or loose- (unconstrained-) particle grinding. The relative efficiency of single-particle comminution, ball-mill grinding and particle-bed comminution in the recently invented high-pressure roll mill is evaluated by making use of the self-preserving nature of the size distributions of comminuted products. The highest energy efficiency can be achieved by utilizing a hybrid two-stage system in which the material is first ground in the high-pressure roll mill and then the ball mill.

Jan 1, 1998

By A. Yehia, J. S. Hu, J. D. Miller, M. Misra

Fluoride activation has been evaluated by Hallimond tube flotation of collophanite in terms of fluoride concentration, conditioning time, pH, and temperature. The results reveal that efficient oleate flotation of collophanite can be achieved by fluoride activation. Experimental results of fluoride adsorption by collophanite suggest that, at low fluoride concentration, a fluoroapatite-type compound may form on the collophanite surface by chemisorption of fluoride ions at calcium sites. At high fluoride concentration, calcium fluoride appears to form at the collophanite surface involving a surface precipitation phenomenon. The formation of CaF2 on the surface of fluoride-treated collophanite is further substantiated by the FTIR spectroscopic measurements, which suggest a metathetic exchange with phosphate from the collophanite lattice during the surface precipitation process.

Jan 1, 1988

By Sukumar Bandopadhyay

In recent years planning of surface mines in general and reclamation and post-mining land uses in particular have become very complex. Due to the lack of suitable techniques, land use plans are rarely based upon structured decisions. Data collection may be conducted in a rigorous manner and certain analyses may be performed on the data; the decision to put the land to a specific use, however, is finally based upon the intuitive judgment of one or several individuals. This paper demonstrates how techniques from fuzzy set theory can be used in order to select an optimum post-mining land use plan. The various land use planning alternatives have been characterized according to both qualitative information and quantitative factors and the "fuzzy" aspects of the collected information are incorporated into the analyses. In a practical application, the methodology is used to obtain the most reasonable solution to a post-mining land use planning problem in Interior Alaska.

Jan 1, 1986

By David McGregor, Ashoke SenGupta, Jerry Darlington

The stability of bentonite clay suspensions against flocculation in the presence of certain anionic polymers was investigated. These polymers included a purified sodium lignosulfonate, a sodium oxylignosulfonate, a potassium salt of humic acid, and a sodium polyacrylate. The polymers differed from one another in molecular weight as well as in carboxylic, phenolic, and sulfonate group contents. The scope of this study is in evaluating the extent of thinning achievable in a bentonite clay suspension in the presence of these anionic polymers under varying electrolyte concentration, presumably as a result of deflocculation of the clay platelets by the polymers. Under certain conditions of polymer dosage and electrolyte concentration, the lignosulfonate seemed to have flocculated the clay suspension, while the other polymers served fairly well as a deflocculating/dispersing agent. The lignosulfonate, however, showed some deflocculating ability when the electrolyte concentration of the suspending medium (water) was increased by adding sodium chloride to the clay suspension. Among the four polymers tested, the polyacrylate was found to be the most effective in deflocculating clay particles, followed by the humate and the oxylignosulfonate.

Jan 1, 2003

By C. P. Lazzara, F. J. Perzak, C. C. Hwang, C. D. Litton

Fire development and spread along conveyor belts in ventilated ducts were investigated experimentally and theoretically. Various types of conveyor belts used in mining applications were ignited and burned in a full-scale gallery under various flow conditions. The flame spread rates depended strongly on the ventilation air speed. The time-temperature traces of gas and belt obtained at 12 feet from the entrance show that a rapid belt surface temperature change takes place prior to a change in the gas temperature, indicating that radiative heat transfer from the flame to the belt surface plays an important role. Further, anomalies in the flame spread rate in the vicinity of 1.5 m/s air speed (i.e., much greater rate than that observed at either higher or lower speeds) can be explained through the mechanism of flame tilt and the resultant view factor between the flame surface and the belt surface. In order to correlate the fire spread with material properties of the conveyor belts (such as the specific heat, the thermal conductivity, and the pyrolysis temperature) and the fire environment (such as the gas temperature and the ventilation air speed), a theoretical model has been developed. This model is based on the experimental observation that the radiative heat transfer is the dominant mode of energy transfer ahead of the flame front. Agreement between the theory and the experimental results is good.

Jan 1, 1991

By J. Felipe Costa, Andrew H. White, Marcot T. M. B. Vilhena

Ordinary kriiing (OK) is an interpolation algorithm mostly used in earth sciences applications where it provides satisfactory results. Robust kriging (RK) is an alternative algorithm which at- tempts to minimise the problems caused by the existence of outlier values within a given data set. Robust kriging essentially consists of an editing step prior to running the traditional OK method. This study compares the interpolation results obtained by OK and RK. Two data sets were used. The first data set consists of 140 samples mimicking a drilling survey named cluster.dat. An additional feature of this sample data is that its parent population, the reference data set, is available, thus permitting direct quantitative assessment of the effectiveness of a given estimation technique. The second data set consists of a grid sampled at 1x1 m. The estimates obtained by OK and RK using cluster.dat were compared to the reference data set. RK provided better results in terms of quality of the estimates than OK

Jan 1, 1996

By M. G. Karfakis

This paper examines the chimney occurrences in the Hanna Coal Field, Wyoming. Chimney caving is defined, previously proposed mechanisms involved in the development of a chimney are critically reviewed, and factors controlling chimney cave are identified. The main portion of this paper deals with the identification and characterization of chimney subsidence due to underground coal mining in the Hanna Mining District. In an attempt to characterize the subsidence, sink-hole occurrences are correlated with the depth of coal, thickness of mined-out beds, mining methods, nature of overburden, structural geology, and hydrology. Most sinkholes in the Hanna Basin appear to be conical in profile, with the apex upward. The average diameter is 15 meters (50 feet), with an average depth of 11 feet. Most have developed above an overburden of less than 61 meters (200 feet). The average mining height to width ratio is 5. Much of the chimney development is governed by the thickness and character of the overburden, the width and height of the mine opening, and the in situ state of stress.

Jan 1, 1986

By F. M. Doyle, Jun Li, Milton E. Wadsworth, Ximeng Zhu, E. Peters

The electrochemical behavior of pyrite in borate/sulfate solutions was investigated using cyclic voltammetry. Three anodic peaks at approximately -0.8 V, -0.1 V and +0.5 V (SCE) were detected along with their corresponding reduction peaks. The first two peaks correspond to the oxidation of surface products. The third peak corresponds to the direct oxidation of pyrite with reaction products FeO oxides. sulfate ion and partially oxidized sulfur intermediates present as a surface film of polysulfides and So. The Few oxides and sulfur intermediates were reduced to ferrous hydroxide and HS during the negative-going scan. The HS interacted preferentially with Fe(OH), on the surface to form FeS. Excess fenous hydroxide continued to reduce to metallic iron. During the return positive-going scan, metallic iron was oxidized to ferrous hydroxide and FeS was oxidized to pyrite. These reactions are characterized by a unique double peak observed in the region -0.8 to -0.65 V. The growth kinetics of the surface sulfur film formed during anodic oxidation were studied using chronoarnperomeay. Potentiostatic measurements were well correlated by a paralinear rate equation, suggesting the formation of an intermediate passive film, associated with the simultaneous dissolution of the outer layer of the film. The reaction rates were affected by applied potential, solution pH and temperature, but were independent of electrode rotation speed. A reaction kinetics model which fitted well with experimental results, was developed.

Jan 1, 1993

By R. Bernard

This paper will discuss innovative strategies that combine the capabilities of an Enterprise Asset Management (EAM) solution, sometimes referred to as a Computerized Maintenance Management System (CMMS) and E-Commerce solutions. Strategies discussed include solutions that minimizes the costs of operations through maximized equipment productivity and availability. Thusly, achieving the ultimate goal of keeping the cost per production unit as low as possible.

Jan 1, 2001

By R. J. Pruett, J. Yuan

Kaolin clays from five different commercial deposits in Georgia were studied to understand the variations of zeta potential and related fundamental properties. The results suggest that higher negative zeta potential is related to exchangeable or soluble calcium ions in the clays.

Jan 1, 1999

By John P. Fillion

This paper will present an overview of conveyor haulage systems. Technical and economic feasibility will be examined as conveyor haulage is applied to large western surface coal mines. Theoretical analysis and actual cases will be presented from NERCO Coal Corp. experiences in bringing this application to their Western mines.

Jan 1, 1989

By V. Nemec

The paper deals with further progress of the space and time models achieved since some of the previous APCOM symposia (1970, 1975, 1980) where original methodology was presented. Various transformations, de- and retectonization of space models, transfer of patterns, interactive time models are among the most important improvements. Enlarged possibilities of practical applications of the developed system are shown.

Jan 1, 1986

By B. D. Nichols, R. Idzorek, W. S. Gregory

A numerical procedure to model flow networks using a node-based approach is discussed, and the analysis encompasses both steady-state and transient solutions. A family of computer codes has been developed using the node-based approach. This technique is illustrated by applying two of the computer codes to mine ventilation networks.

Jan 1, 1987

By Thomas J. Lien

AMAX Coal Company has constructed the first commercial demonstration sub-bituminous coal dryer at its Belle Ayr Mine south of Gillette, Wyoming. This 215 ton per hour facility is projected to produce 165 tons per hour of dried coal at 10 percent moisture and 10,800 Btulpound (6,000 KCIkg). Approximately 43 tons per hour of water will be removed from the coal and seven tons per hour of coal burned as fuel.

Jan 1, 1989

By Conrad Parrish

As originally conceived, this paper was to address the costs of environmental compliance, focus on environmental impact statements, and describe how those costs impact mining projects. The intent was to do wide ranging mathematical analyses to demonstrate the varying impacts on mining projects depending on their size, timing, return on investment and other salient project features. The initial portion of the numerical analysis necessary to this purpose was performed. The results showed a pattern of impacts familiar to the mining industry:

Jan 1, 1991

By J. B. Yianatos, G. S. Dobby, J. A. Finch, A. R. Laplante, R. Espinosa-Gomez

The question is posed as to why columns typically have a collection zone 10 m high (H) by 1 m in diameter (D). Three geometry dependent factors are considered: degree of mixing, Np; volumetric bias rate, B; and volumetric gas rate, G. Increasing H:D decreased Np and B, which improves performance but decreases G, which causes the column to approach overloading. Taking typical column operating conditions, it is concluded that a collection zone H:D of 10:l is a reasonable compromise.

Jan 1, 1987

By A. C. Noble

Ore reserves are often less than 30% of the geologic resource estimates initially prepared by exploration geologists. Differences of this magnitude can lead to serious problems in the early valuation of properties when the geologic resource estimates are interpreted to represent ore reserves but are later found to be misleading and gross overstatements of the actual ore tonnages. The geologist can avoid such difficulties by considering the implications of mining, metallurgical recovery and economics early in the project and by using appropriate qualifiers in the resource statement. Examples using typical deposit characteristics are used to demonstrate how the cutoff grade, stripping ratio, dilution, mining extraction and metallurgical recovery affect ore reserve estimations.

Jan 1, 1994

By I. J. Jansen, C. L. Hooks

Successful soil construction involves prepa¬ration of an adequate base, selection of high quality soil ma¬terials, and placement of those materials by means which will establish a continuous macropore network and modest to low soil strength. Where such has been accomplished, experi¬ments reveal row crop productivity on reclaimed land which is very competitive with that on undisturbed land. Inferior productivity and sensitivity to drought stress are experienced where the soils are excessively compacted during construc¬tion. Some deep tillage practices have been quite successful in improving the compacted soils, but it is preferable to avoid compaction as the soil materials are handled.

Jan 1, 1987

By R. Sripriya, Ch. V. G. K. Murty, N. D. Rao, P. V. T. Rao, A. Ramu

Studies were carried out to improve the performance of hydrocyclones at Tata Steel's chrome ore beneficiation plant in Sukinda, India. The optimal cut point of the hydrocyclones was determined in the laboratory using a stub cyclone. In the tests, the operating and design variables, including spigot diameter, density of feed slurry and inlet pressure, were varied. Subsequently, plant trials were carried out, and attempts were made to develop a model of the hydrocyclone using the Rao, Lynch and Plitt model. The cyclone efficiency was represented by the parti¬tion curve, and the performance was evaluated mathematically from a reduced efficiency curve, represented by the equation:

Jan 1, 2000

By J. Partyka

Fumes produced during blasting operations in underground mines are defined in this paper by an equivalent contaminant source. The primary goal is to establish a method which would allow all those parameters not measured directly to be determined reliably from field data. The parameters to be identified are the diffusion coefficient , and the position and size of an equivalent source. The diffusion-value is computed from the peak concentrations taken by two monitors located in the drift. The first monitor is placed close to where blasting pollutants join the main stream, while a second monitors is moved downstream a some distance from the first point. The position and size of the dust source and the total amount of dust produced during blasting are determined from the data recorded by only one monitor.

Jan 1, 1991