Search Documents

By V. Badaker, R. J. Sweigard, C. D. Barton, J. W. Stringer, J. M. Ringe, A. D. True, D. H. Graves

Field studies have demonstrated the relationship between the growth of high-value trees on surface mined land and the physical conditions of the root growth medium. Specifically, the survival and height of hardwoods grown on less compacted material are far superior to those grown on compacted material. Furthermore, studies have demonstrated that the physical condition of the root growth medium can be characterized by dry bulk density and penetrometer resistance and that these parameters are also related to tree growth measurements. Site indices are useful for evaluating and predicting the productivity and timber yield for a specific location. A method has been proposed to estimate the site indices for various tree species on reclaimed surface mined land as a function of the physical properties of the root growth medium.

Jan 1, 2005

By R. M. Balderrama

Bench-scale laboratory flotation and gravity separation tests were conducted on tailings samples to remove the sulfidic material, mainly pyrite, the source of acid generation. A combination of xanthate collectors, promoters, and frothers were used during flotation. Pyrite recoveries were in the range of 42 to 97%, depending on the tailings being treated. Sulfide sulfur contents of 12.8 to 0.37% in the feeds were reduced to 8.68 to 0.01% in the treated tails. Flotation tests were conducted to evaluate the ARD potential as a function of percent pyrite remaining in the tails. Standard ARD predictive tests were used to evaluate the success of the treatment. In some cases, removal of only 50 to 55% of the pyritic fraction was required, thereby demonstrating the conversion of the waste material from acidic to non-acidic. A laboratory vanning table was used to evaluate the amenability of sulfide-bearing tailings samples to gravity separation. The pyrite recoveries varied from 38 to 86%. The sulfide sulfur content of 12.8 to 0.37% in the feeds was reduced to 6.0 to 0.14% in the treated tails. Predictive ARD tests performed on tailings before and after the gravity removal of pyrite showed that most samples changed from "probably" acid producing to the "uncertain" range. Data reported and analyzed in this paper demonstrate source control for ARD prevention through the removal of metal sulfides from sulfide-bearing wastes using conventional flotation and gravity separation techniques.

Jan 1, 1995

By N. R. Sainath

This paper discusses a laboratory investigation that studied the microscale flow characteristics of copper ores and the variation in flow behavior resulting from flow of leach solution. Fractures in 40- and 100-mm-diam (1.5- and 4-in.-diam) cores were first mapped by visual inspection. The permeability of cores to water-stressed in a triaxial stress field representative of in situ conditions - was estimated. The samples were then exposed to 20g/L (2.7 oz/gal) sulfuric acid and the experiment was repeated. The porosity and the rate of recovery of copper from the specimen during leaching were also studied. The measured permeability of unleached samples with no visible fractures ranged from 10-16 to 10-19 m2 and it increased as leaching progressed. The porosity increased significantly with leaching, while the rate of copper recovery decreased.

Jan 1, 1994

By Slavoljub D. Maksimovic, Steve J. Page

The Bureau of Mines measured respirable dust emission rates from overburden drilling at a surface coal mine and the transport of this dust to downwind locations. The emission rates were estimated by using multiple gravimetric dust samplers mounted on a cross-shaped tripod located immediately downwind of the drill. The transport of this dust was measured at more distant downwind locations by a combination of respirable gravimetric sampling and integrated bag sampling of sulfur hexafluoride (SF6), which was used as a tracer gas. Two modes of sampling were used: (1) At five sampling locations arranged in a semicircle around the drill. The radius of this arc ranged from 15.85 m (52 ft) to 71.32 m (234 ft). (2) In-line sampling at downwind locations with samplers located at intervals of either 10.67 m (35 ft) or 15.24 m (50 ft) for a total distance of 76.20 m (250 ft). Samples were taken 1 .22 m to 1.52 m (4 to 5 ft) above ground level. Test results for the semicircular test arrangements showed that at any downwind location, the maximum contribution of respirable dust due specifically to the drilling operation was 42%; the average for eight tests was 13.6%. In general, there was no correlation between the downwind distance of this maximum contribution and the maximum contribution itself because of changing wind direction. Test results for the in-line arrangements indicated that the transport of the dust from the drilling operation usually decreases rapidly with distance and that, even though the drill dust may produce significant health hazards for the drill operator and drill helper (or other personnel in the immediate vicinity), the exposure of downwind personnel to drill-generated dust may not be a significant problem.

Jan 1, 1987

By John Nadolski

Intensive hydrologic monitoring of the Powder river basin has been on-going since the early 1970's. Data were used in environ- mental assessments and for determination of hydrologic consequences associated with coal mining activities. For most coal mine operators, data collection has continued in this baseline mode with little or no statistical analysis of the data and with no statistical procedure established to detect changes in groundwater quality. For the past four years Powder River Coal Company has studied several statistical techniques to analyze groundwater quality. Three objectives were pursued: 1) to determine the baseline water quality for key aquifers; 2) to determine which wells could be deleted from the monitoring program without reducing monitoring effectiveness; and 3) to define a statistical test to determine water quality changes. Knowledge of the regional geo-hydrologic system was combined with an analysis of the water quality monitoring in order to identify homogeneous aquifer zones. All wells within an aquifer zone were treated as one population, and a t-test was used to determine the minimum number of samples needed to define the water quality for each aquifer zone. Results indicate that the data for each aquifer zone were nor- mally distributed and that groundwater quality could be defined using a fairly small number of samples. Because of the minimum sample size test, groundwater quality sampling was reduced by between 75 and 85 percent.

Jan 1, 1989

By J. M. Mutmansky

This paper outlines the results of a study of the opinions of practicing engineers concerning the value of environmental engineering courses in a mining engineering curriculum. One hundred engineers with significant experience in mining-related engineering work were carefully chosen. Of the 67 responses, about half were from mining engineers, and the other half were from environmental engineers. In this paper, the results of the survey are outlined. The number and type of courses recommended by the respondents are summarized as well as the specific topics recommended for inclusion in a mining engineering curriculum. The survey form also asked for the stages in the mine life when environmental experts were needed and the percentage of environmental engineering performed by outside experts for many mining-related environmental tasks. The results of this line of questions are provided. Finally, the paper offers a comparison of the results for environmental engineers and mining engineers and analyzes the differences.

Jan 1, 2003

By H. K. Lin

Cyclic voltammetric and potential step chronoamperometric techniques were used to study gold dissolution in cyanide solution. Three distinct anodic peaks and one cathodic peak appear on the voltammogram between -0.50 and 0.80 V vs. SCE. The corresponding reactions were proposed to explain the peaks and the passivations. The proposed reactions were in agreement with the effect of pH and cyanide on the magnitude of the peak currents. Cyclic voltammetric tests, with various vertex potentials, were also conducted to examine the proposed reactions. Steady-state currents at various potentials were obtained by potential step chronoamperometric technique and were compared with transient currents obtained by the cyclic voltammetric technique.

Jan 1, 2002

Political events during the past decade have caused businesses throughout the world to think globally. Countries once closed to free market enterprises are now open and seeking out foreign investment to help improve the well being of their populations. The mining industry has always been a global one. Today, though, the industry has become even more global. The driving forces behind this include the opening up of higher grade, lower cost mineral deposits in undeveloped and developing nations. In addition, permitting delays in the United States, coupled with stricter environmental guidelines and a general anti-mining attitude, have forced the mining industry to look outside US borders. The Mineral Economics and Management Society (MEMS) took as the theme of its seventh annual professional program "Economic Globalization of the Mining Industry." About 100 people attended the conference held in Arlington, VA in late March. Speakers included members of the investment community, academia, government and the mining industry.

Jan 1, 1998

By M. Abdel-latif, R. W. Bartlett, P. R. Taylor

A cyclone reactor system for the partial reduction and melting of taconite concentrate fines was designed and operated. A nontransferred arc plasma torch was employed as a heat source. Taconite fines, carbon monoxide and carbon dioxide were fed axially into the reactor, while the plasma gas was introduced tangentially into the cyclone. The average reactor temperature was maintained above 1673 OK (1400°C), and reduction experiments were performed under various conditions. The influence of the following parameters on the reduction of taconite was investigated: carbonmonoxide to carbon dioxide inlet feed ratio, carbon monoxide inlet partial pres- sure and average reactor temperature. The interaction of the graphite lining with carbon dioxide and taconite were also studied.

Jan 1, 1995

By A. Vargiu, R. Ciccu, G. Massacci

Based on the current results of field practice and on experimental data obtained in the laboratory with a suitable testing apparatus, the industrial operation of diamond wire cutting can be simulated by means of a mathematical model capable of predicting the cutting velocity and the wear rate of the tool, and thence the cost figures, achievable for a variety of conditions (kind of rock, size and shape of the cut, position of the equipment) according to a predetermined setting strategy (peripheral velocity, pull- back force). The paper gives a short outline of the model and discusses the simulation results obtained in a number of cases aiming at singling out the most favourable conditions for a cost-effective use of diamond wire.

Jan 1, 1996

By D. D. Harbuck, G. K. Green

The Bokan Mountain area on Prince of Wales Island, AK, contains vast quantities of heavy rare earth minerals. To lessen the US dependence on foreign sources, the US Bureau of Mines (USBM) investigated yttrium recovery from this ore. By sulfating the ore at 250 ° C for 1 hr at an H2S04:ore ratio of 1:1 and then water leaching the sulfated material for 1 hr at 20% solids and 25ºC, over 74% of the yttrium, cerium, and lanthanum were solubilized. Solvent extraction (SX), using a synergistic combination of OPAP and DEHPA, selectively loaded 100% of the yttrium. Yttrium was stripped directly as a solid using a 2M, 35 ° C NaOH liquor. When the OPAP/DEHPA mixture was tested in a continuous SX circuit, yttrium loading and stripping were 100% and 96%, respectively. The organic showed excellent recyclability properties with minimal solvent loss.

Jan 1, 1996

By Bob Gordon, Allen Furth, Dan Dobbels

A 4.8 m (16 ft) diameter hard rock tunnel was driven through granite bedrock to create the 1.7 kilometer (1.1 mile) long Hampton McCloy Retention Tunnel for the city of Richmond, Virginia. During the work the tunnel encountered narrow seams of partially decomposed granite that were not self supporting and could be dealt with using ribs and lagging. However, as the tunnel approached the receiving shaft, it encountered a large seam of highly decomposed rock, alluvial deposits and running sand which resulted in soil loss into the machine. As a result of this condition, a jet grouting program was quickly developed to allow the tunneling to continue. This paper will describe the manner in which jet grouting was used to solidify and stabilize the decomposed bedrock, alluvial soils, and running sand to allow the TBM to continue tunneling.

Jan 1, 2003

By R. Mensah-Biney, M. T. Hepworth, K. J. Reid

The kinetics of gold-bromide loading onto activated carbon was investigated in a batch stirred reactor. Based on a second-order equation, the amount of gold adsorbed by the carbon was correlated with time. From a 30ºC solution containing 25 ppm Au and 0.8 g/L carbon, the rate constant for gold-bromide species onto activated carbon ranged from 0.27 x 10-3 to 1.2 x 10-3 (kg/t)-1 min-1. The equilibrium saturation capacity (Qe) was 36 ±3.0 kg/t from the same system. The rate of loading increased with increasing temperature and decreasing particle size, pH and solution gold concentration. The calculated activation energy (Ea) was 8.8 kcal/mole, significantly higher than those reported for physical adsorption. The equilibrium saturation capacity (Qe) increased with increasing concentration of gold in solution but was independent of other variables such as temperature, agitation speed, particle size and pH. These rate constants and equilibrium saturation capacity for the gold-bromide species are higher than those reported for the gold-cyanide systems.

Jan 1, 1998

By R. J. Matetic, Peter G. Kovalchik, Jeffrey Shawn Peterson

The National Institute for Occupational Safety and Health (NIOSH) has initiated a study of a roof bolter to reduce noise exposure to mine roof bolter operators. An important segment of this research entails determining the affect of various drilling configurations on the performance (penetration rate) and sound power emissions when drilling into granite. Test conditions included various combinations of rotational speeds and thrusts; hex and round drill steels of one inch (1.) and one and three-eighths inch (1 3/8.) diameters; vacuum and wet conditions; and using drill media of differing compressive strengths. This paper will detail the affects of each of these on the performance and sound power level emission. When drilling into granite, it was found that wet drilling generated lower sound power levels and performed better than vacuum drilling.

Jan 1, 2005

By S. Subbarayan, S. Chander, M. S. Klima

A laboratory study was conducted to investigate the potential for recovering anthracite from coal preparation-plant tailings. The study included washability analyses, cyclone simulations and froth flotation testing Samples were collected from either the tailings streams or the slurry ponds of five anthracite-cleaning plants. From each sample, a washability analysis was conducted on the 28x100 and 100x200-mesh fractions. Using the above data, along with published partition data, simulations were performed with various cyclone-staging arrangements for both water-only and dense-medium cyclones treating the 28x200-mesh fractions. Separate froth -flotation tests were conducted on the 28x100- and 100x200-mesh fractions from three of the plant samples. The washability, simulation and flotation results are presented as grade-yield curves.

Jan 1, 1996

By R. M. Damodaran

The flotation performance of Florida phosphate rock was evaluated in terms of the mixing behavior of reagents and particulates during anionic conditioning of phosphate slurries. The various conditioning variables that influence mixing, namely, solids loading, agitation speed and conditioning time, were investigated to determine their effect on reagent coating of the particles. The phosphate recovery was used to monitor the conditioning efficiency. The mixing characteristics of the phosphate feed were evaluated in terms of the ratio of the mixing power (P) to the minimum power (Pm) required to keep the slurry in suspension. It was found that mixing conditions govern the conditioning time required to obtain a high recovery. Reagentization was slower at lower P/Pm ratios. At higher P/Pm ratios, the flotation recovery was optimized, and the agitation speed was found to have no significant effect. Optimum mixing conditions were obtained for a74 wt% slurry at an agitation speed of 450 rpm (47 radians/sec). Under these optimum mixing conditions, the collector dosage required for an improved recovery was lower and the conditioning time was shorter.

Jan 1, 1997

By M. T. Ityokurnbul, M. P. Trubelja

Concentrate flow rates were measured for the flotation of -100-mesh Lower Kittaning coal in a computer-controlled 0.076 x 3.5-m pilot flotation column. The variables studied were recovery zone height, airflow and solid feed rates. The specific projected surface areas of the feed, concentrate and tailing streams were determined from the measured particle size distributions. The results obtained show that the concen¬trate flow rate was independent of recovery zone height but was dependent on the hydrostatic pressure setting (measure of froth depth), gas flow rate, solid loading and particle size. New correlations for column carrying capacity and yield are provided as a function of bubble surface area flux and the specific particle projected surface area.

Jan 1, 1999

By J. Hanna, I. Anazia

Selective fatty acid flotation of carbonate gangue from sedimentary apatites was achieved under acidic pHs without a specific apatite depressant and without conditioning the pulp with the collector. Concentrates (35% to 38% P2O5, 0.8% to 1% MgO) with high recoveries (80% to 85%) were produced from Indian and Chinese dolomitic ores. The calcareous and/or dolomitic-siliceous phosphate ores of South Florida and Utah required two flotation stages: one for carbonate removal, as mentioned above, and the other for phosphate recovery from siliceous gangue. Preliminary tests on the South Florida ore gave concentrates analyzing 29% P2O5 and 0.8% MgO, with a P2O5 recovery of 76%. A concentrate obtained from the western US phosphate ore from Utah assayed 30% P2O5 and about 1% MgO, with a P2O5 recovery of 89%.

Jan 1, 1988

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 Cliff G. Paton, Sheldon B. Bland, Roger E. Melley

This paper looks at four critical lubricants used in the conveyor systems of the northern Albertan oil sand facility. The requirements for the lubricants used in the electric motors and gear boxes of the drive systems, the pulley bearing and the idler bearings are discussed in terms of the applications and the environment. A number of developments that have occurred in recent years are presented. Data from the field and from custom designed testing in the laboratory are used to support the role of simulation testing in problem solving in this area of technology.

Jan 1, 1996