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By F. W. Petersen

In the precious metal industry, activated carbon is used extensively for the recovery of gold and silver from cyanide solutions, particularly from slimy pulps and unclarified solutions. However, carbon can easily become fouled by inert particles in the pulp, thus decreasing the activity or gold loading of the carbon. This paper attempts to quantify the distribution of fine inert particles in activated carbon. Furthermore, a possible mechanism for the intrusion of fines will be postulated. Precipitated silica and ground silica sand were used to simulate pulp conditions and their loadings on activated carbon were determined by ashing. The kinetics of intrusion of fines into the pores of carbon were relatively fast, and were dependent on the concentration in the pulp. Results indicated that particle size of the solids and zeta potential of the fines influenced the loading of inert species on carbon. Scanning electron microscopy and secondary ion mass spectrometry showed a decrease in solids concentration to the centre of the carbon particle.

Jan 1, 1995

By B. Moudgil, M. Bogan

A bench-top centrifuge was used to study the consolidation behavior of phosphatic clays. A mathematical model (based on, first-order kinetics) was developed to describe the relationship between the void ratio (at any time) and the effective stress. The permeability of the sediment as a function of the void ratio is also described. The results of this analysis are then compared to data obtained by other consolidation testing methods. The centrifuge results indicate that consolidation data may be developed in a short period of time (hours) as compared to days or weeks when other techniques are used.

Jan 1, 1997

By W. H. McDonald, D. D. Carr

The use of stone in building construction predates written history. From the time that stone was first used, builders have constructed stone buildings predominately from local or regional materials. However, since World War II, the stone business has become increasingly global. For example, French limestone is now sold to builders in the United States, and American granite is shipped to Japan. The internationalization of architectural and construction firms has encouraged this trend. Differences among nations in trade practices, environmental demands and the level of knowledge of dimension-stone characteristics make international trading in stone a risky and potentially disastrous business for unwary participants.

Jan 1, 1997

By Andrew J. Neale, Mark Franklin, Mike Cooper

Although recent advances have significantly improved our understanding of flotation fundamentals, disturbance variables combine to make it difficult to maintain steady state operating conditions over either the short or long term. One of the major concerns relates to knowing how much reagent to add to the flotation system, how to monitor the addition rate, and how to determine when to adjust the reagent addition rate in the presence of these disturbances. This paper will look at the development and installation of process control systems that address these issues. The economic benefits that accrued from the implementation of these strategies is described.

Jan 1, 1994

By Angus M. Henderson, Charles R. Lilley

Underground mining at Kanowna Belle commenced in July 1998, using a sublevel open stoping method. The use of this stoping method necessitated the use of a cemented fill material for filling primary and secondary stope voids. A detailed engineering study recommended the construction of a cemented aggregate fill (CAF) system for Block A, in favour of paste fill. The CAF system consisted of a crushing and screening plant, a surface binder preparation plant and an underground fill station. Conventional underground dump trucks were used for CAF delivery. Since CAF plant commissioning in March 1999, 1.2 million tonnes of CAF have been placed underground. CAF segregation was the most significant quality control issue during CAF system operation. At the hangingwalls of filled stopes, CAF segregation sometimes occurred to such the extent that the resulting fill material was essentially uncemented coarse aggregate. This caused some CAF dilution during the extraction of adjacent secondary stopes. Numerous CAF were prepared on site for strength testing. A relationship has been formulated that allows estimation of the CAF uniaxial compressive strength in MPa, based on the cement content (c) and porosity (n), as follows. [ ] Practice at Kanowna Belle has confirmed that laboratory testing results cannot be applied for optimising the mix design of cemented rock fills that do not exhibit debris flow behaviour during placement. The grain flow characteristics and consequent marked segregation dominate the in situ fill strength. A detailed review of backfill requirements for the lower mine indicated that the total net present cost of CAF and paste systems was similar. Several significant operational advantages offered by a paste system have resulted in its selection for the remaining mine life. The construction of a paste fill system at Kanowna Belle is currently in progress.

Jan 1, 2001

By Xi Huang

The coal workers' pneumoconiosis (CWP) has been considered as the most serious health problem in the coal mining industry. The development of CWP in a worker lung depends on the average concentration and toxic components of the coal dust and the exposure length. Toxicity studies on coal dust shows the bio-available iron (BAI) in the coal dust plays an adverse role in the CWP development. It is also found that presence of calcite in the coal seams can significantly reduce the CWP cases as evidenced by the significant difference between the coal miners in the western and Appalachian coal regions. Based on this finding, it is proposed to artificially introduce calcite to BAI -containing coals in the effort to mitigate the CWP disease in coal industry. This paper introduces the scientific bases, the main geological factor that makes the differences, the proposed methods to introduce calcite to coal dust or to coal seams. Feasibility for the proposed methods is also discussed.

Jan 1, 2013

By R. D. Schmidt, M. J. Friedel

Unsaturated permeability and flow capacity exist where copper mineralization is disseminated in segmented, very-low-permeability ore blocks. The US Bureau of Mines (USBM) investigated this condition for application to in situ, copper-leach mining at the Cyprus Casa Grande mine site. Moisture retention properties are derived and combined with scanning-electron-microprobe data to characterize the host rock's mineralogy, texture, pore size, distribution and permeability. Finite element modeling is used to estimate saturated permeability and the ambient degree of saturation and to gain insight into appropriate in situ leach design. Recommended design modifications for optimized solution distribution and maximum recovery from the Casa Grande ore require: • well pressure injection exceeding 1500 psi and recovery wells operating in a suction mode, or • secondary, permeability enhancement by explosive rubblization. In the former, the lack of conditioning and the use of lesser pressures will result in leach solutions confined to the macrofractures. With the latter requirement, pressures can be reduced to 500 psi, with improved recovery and solutions containment.

Jan 1, 1993

By John A. Herbst, Per-Olaf Samskog, Jan Bjorkman, Yi Chang Lo

The study described here is concerned with the development of a model for the simulation and optimization of a rod milllpebble mill circuit. A series of laboratory tests was conducted to investigate the effect of critical operating variables. The pebble mill model structure used was a population balance type which accounta for impact breakage and fines production from pebble wear. Model parameterization and verification were performed using data obtained in batch tests and in a plant test campaign. The model developed was found to provide accurate predictions of plant-scale grinding. The prediction errors are less than 21 for the product size and 31 for the mill power required to achieve that product with a mill volume scale-up of 14,000 to 1. These results indicate that accurate extrapolations from laboratory batch data to plant scale performance are poaaible using the population balance model and scale-up prediction procedures for pebble mill circuits as well as ball mills. Preliminary indications are that the new model developed here will provide vital input for pebble mill optimization and process control as well as pebble mill design.

Jan 1, 1990

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 Charles Fisher

When considering the biodiversity of fauna endemic to hydrothermal vents or hydrocarbon seeps one must consider not only the numbers of unique species, but also the physiological diversity (and potential biochemical/physiological uniqueness) of the fauna. The deep ocean ridge system is home to some of most extreme animal habitats found on Earth. In addition to the high pressure, low temperature, and lack of light characterizing the deep-sea in general, hydrothermal-vent environments are characterized by toxic chemicals and temperatures that would be hostile to most other animal life. Perhaps even more challenging than the absolute levels of chemicals, dissolved gases, and temperature with which vent animals contend are the extreme gradients in time and space of all of these parameters. For example, temperatures around some vent animals can fluctuate from ice-water to hot-tub levels over seconds and can exceed 350°C only inches away. Specially adapted animals not only tolerate these conditions, they often thrive under them. As a result, the biomass of many deep ocean ridge ecosystems rivals that of coral reefs and tropical rain forests. In the Gulf of Mexico, hydrocarbon seepage through the sea floor driven by salt tectonics results in environments that are geologically very different from hydrothermal vents, but are geochemically similar enough that closely related animals are found in the two habitats. This includes seep mussels, clams, shrimp, worms, and other animals whose close relatives are found in hydrothermal vent environments. Although many aspects of the biology of the animals from the two environments are very similar, there are also significant differences in their life histories and physiologies that reflect the fundamental differences in the geology of their habitats.

Jan 1, 2008

By D. N. Thompson, R. L. Sayer, K. S. Noah

Economical remediation of acid rock drainage (ARD) at secluded high-altitude western ore mines is difficult given the current treatment technology. Several passive-engineered systems that are based on wetland technology were tested in the laboratory with three western ore mine ARDs (Co, Cu and Fe mines) and with a copper leachate effluent. These systems used well-weathered lodgepole pine sawdust as the sole carbon source and mud from a pond at one of the mine sites as the source of sulfate-reducing bacteria (SRB). Simple one-pass flow-through systems removed 44% to 99% of the vari¬ous heavy metals front the Co and Cu mine ARDs and increased the pH from 3 to 7 after 28 days of SRB acclimation with a five-day residence time. Carbohydrate utilization rates were generally low, except for one 437-day run, which consumed 25%, 30% and 21 % of the cellulose, hemicellulose and lignin, respectively. Initial pH, amounts of toxic heavy metals and the degree of predegradation of the sawdust were found to significantly affect both remediation potential and acclimation time. Engineered SRB systems, alone or in combination with other passive technologies, offer promise for the economical remediation of western US ore mine ARDs.

Jan 1, 2000

By William N. Fitch, Valois R. Shea-Albin

In 1976, the Resources Conservation and Recovery Act (RCRA) aroused concern in the mining community about the regulation of mine waste streams under RCRA. In response, the Bureau of Mines initiated research in the late 1970's that addressed mine and minerals processing waste. Research included investigating improved environmental technology for metal, coal, non-metal, and emerging industries such as oil shale, tar sands, peat, and lignite. Environmental issues escalated in the 1980's. Proposed regulations addressing control technology for mining and mineral processing wastes prompted the Bureau of Mines to become involved in 1985 in an advisory capacity to the regulatory agency, the Environmental Protection Agency. In Fiscal Year 1988, the Bureau of Mines initiated a research program designed to provide the minerals industries with cost-effective solutions for ameliorating environmental effects of mining. Bureau research has led to advances in the areas of acid mine drainage control and mitigation, subsidence prediction and control, and control and treatment of solid wastes resulting from mining and mineral beneficiation. The Bureau also conducts research seeking new methods to remediate abandoned mine lands. A discussion of the mine waste issues is presented, followed by a summary of past and present research conducted by the Bureau of Mines.

Jan 1, 1991

By Waclaw Dziurzynski, Janusz Tracz, Danny Wooton, Andrzej M. Wala

The purpose of this paper is to present validation studies of the mine-fire simulator using data gathered from an actual mine fire which occurred in November 1991 at the Pattiki Mine. This study evaluates the suitability of the computer software package for modeling underground fires. The paper also discusses the importance of the on-line monitoring system for the validation process.

Jan 1, 1995

By Peter Maltby

A $20M pressure oxidation facility is under construction at the Nerco Con Mine, Yellowknife. Plant commissioning will start in the third quarter of 1992. Roasting of arsenical auriferous concentrates prior to 1970 left 45,000 tons each of highly toxic gold-bearing arsenic trioxide sludge and roaster calcine at the minesite. Safe disposal of these wastes has been a high priority. In 1983 an arsenic trioxide plant was built by the former owner to re-treat the sludge and to sell the product. Due to a poor market and high operating losses, the plant was closed by Nerco in 1989. Mine production in the future will revert increasingly to refractory ore as a replacement for free-milling ore which has been the mill feed since the roaster was shut down. With this fact in mind, Nerco management saw the potential of a proven process to recover the gold from a combined feedstock of refractory flotation concentrate, sludge, and calcine waste. A further requirement was the stabilization of all the arsenic as an insoluble ferric arsenate. By the end of 1989, after the completion of a literature search and a study of process economics, pressure oxidation was selected. Extensive bench and pilot plant work was completed in 1990 and early 1991 to develop the process parameters and to complete environmental testing of the autoclave products. Management approval for construction of a pressure oxidation facility was made in December 1990. Plant capacity is 96 tpd requiring a 40 tpd VSA oxygen plant on site. Detailed engineering began in March 1991. The pressure oxidation building was completed by the end of 1991. The autoclave arrived on site and was mounted on its foundation in December 1991.

Jan 1, 1992

By Gerrit V. R. Goodman, Fred N. Kissell

The issue of miner safety in case of an underground mine fire has been extensively examined by both government and industry. These efforts have intensified in recent years following a number of fatal fires at underground coal mines. As a result, there is an increasing interest in the reliability of coal mine escapeways during a mine fire. This paper discusses the use of fault tree analysis for evaluating escapeway reliability. A fault tree is developed using standard logic formulations. It is later evaluated using commercially available software. The computer model uses Boolean reduction to obtain the minimal cut sets and minimal path sets of the tree. A brief analysis is also conducted to determine the occurrence probability of the TOP event. This study shows that fault tree analysis is a viable means of analyzing escapeway reliability. The cut and path sets reveal those event sequences leading to fatalities. Such information is useful in safety training and accident prevention. The probability of the TOP event shows the frequency of occurrence for fatalities in an underground mine fire. The usefulness of this value, however, is limited by the accuracy of the data for the initiating events. For mining events, the data is difficult to estimate precisely.

Jan 1, 1989

By C. L. Karr, D. E. Goldberg

This paper considers optimization of the design and operation of an air-injected hydrocyclone (AIHC) via a genetic algorithm (CAI. The AIHC is a mineral separating device, developed by the U.S. Bureau of Mines, that combines the selectivity of flotation with the capacity and simplicity of hydrocyclones. GA's are search procedures based on the mechanics of natural genetics. Computer results demonstrate the ability of a GA to rapidly locate design and operating parameters that improve AIHC performance. A computer model of the GA-designed AIHC predicts improved recovery over that currently being obtained with an AIHC in operation at the U.S. Bureau of Mines Tuscaloosa Research Center.

Jan 1, 1990

By A. E. Stewart

Slope design in an open pit mine includes determining bench height, bench face angle and berm width. Case histories are presented of two highwall slopes (160 and 220 m or 525 and 720 ft high) excavated in dipping strata in an op¬erating coal mine. These examples illustrate the influence that bench face angle can have on the stability of an entire slope. The two highwall slopes, the lower of which experienced significant instability, were excavated in approximately the same lithologic and structural environment. The main differences between the slopes were the angle at which the bench faces were excavated and the excavating methods that were used. Relevent aspects are also described of the engineering geology, slope design and excavation procedures.

Jan 1, 1998

By S. Odell

The Bureau of Land Management (BLM) has constructed two biochemical reactor systems (BCRs) to treat mining influenced water from the Forest Queen Mine near Silverton, CO. The bioreactors coupled with a natural wetland provide treatment to the Forest Queen Mine drainage. The central objective of this paper is to review the performance of the bioreactors and wetland treatment system. The bioreactors have been in operation for nine years and along with the natural wetland are still removing a high percentage of the influent metals.

Jan 1, 2010

By Y. M. Jiang, D. W. Park, S. M. Lee

A vast majority of longwall operations in the US use shield-type hydraulic supports to provide ground control along the longwall face. The three-dimensional, finite-element technique combined with a progressive failure approach was utilized to simulate interaction between shields and surrounding strata and determine various loading conditions. In addition, a separate finite-element model of the shield structure was made to study responses of each longwall shield to the different loading conditions. Shield responses under various loading conditions and the shield characteristics, such as shield stiffness, the ability of resisting horizontal forces, and the effect of shield height, were studied based on the results from finite-element analyses. The results can provide the basis of effective shield design and be used for evaluation of the shield performance. It is suggested that a technique incorporating the finite-element method be developed to evaluate real-time shield performance for the purpose of effective ground control.

Jan 1, 1993

By Wang Dianzuo, Luo Lin, Hu Yuehua, Qiu Guanzhou

This paper introduces a novel classification approach named the flotation classification approach which works by controlling interactions between particles. It differs considerably from the conventional classification processes operating on mechanical forces. In the present test, the micro-bubble flotation technology is grafted onto hydro-classification. Selective aggregation and dispersion of ultrafine particles are achieved through governing the interactions in the classification process. A series of laboratory classification tests for -44 pm kaolin have been conducted on a classification column. As a result, about 92 percent recovery for minus 2 pm size fraction Kaolin in the final product is obtained. In addition, two criteria for the classification are set up. Finally, a principle of classifying and controlling the interactions between particles is discussed in terms of surface thermodynamics and hydrodynamics.

Jan 1, 1995