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By Xun Zhang, Hang Qiu, Andrea R. Gerson4, Shaomin Lei, Yubiao Li, Yu Meng, Zhenyu Pei, Min Lin

Efficient separation of trace muscovite from the surface/interface of quartz grains was accomplished during oxidizing calcination and catalytic pressure leaching of the hydrothermal quartz. Experimental results suggest that 98.97% or more of the muscovite was separated when quartz sand was calcined at 900 °C for 5 h and then leached by hydrochloric acid and ammonium chloride solutions as substitutes for leaching agents containing fluorides. The chemical processing techniques show high selectivity in purifying quartz sand by transforming mineral muscovite into active structures during oxidizing calcination, and then dissolving the active substances during catalytic pressure leaching

By M. K. Mohanty

One of the main objectives of this study was to evaluate a fine-coal cleaning circuit using an enhanced gravity separator specifically for a high sulfur coal application. The evaluation not only included testing of individual unit operations used for fine-coal classification, cleaning and dewatering, but also included testing of the complete circuit simultaneously. At a scale of nearly 2 t/h, two alternative circuits were evaluated to clean a minus 0.6-mm coal stream utilizing a 150-mm-diameter classifying cyclone, a linear screen having a projected surface area of 0.5 m2, an enhanced gravity separator having a bowl diameter of 250 mm and a screen-bowl centrifuge having a bowl diameter of 500 mm. The cleaning and dewatering components of both circuits were the same; however, one circuit used a classifying cyclone whereas the other used a linear screen as the classification device. An industrial size coal spiral was used to clean the 2- x 0.6-mm coal size fraction for each circuit to estimate the performance of a complete fine-coal circuit cleaning a minus 2-mm particle size coal stream. The ?linear screen + enhanced gravity separator + screen-bowl circuit? provided superior sulfur and ash-cleaning performance to the alternative circuit that used a classifying cyclone in place of the linear screen. Based on these test data, it was estimated that the use of the recommended circuit to treat 50 t/h of minus 2-mm size coal having feed ash and sulfur contents of 33.9% and 3.28%, respectively, may produce nearly 28.3 t/h of clean coal with product ash and sulfur contents of 9.15% and 1.61%, respectively.

Jan 1, 2008

By J. J. Carlson

Studies were carried out to determine whether filtration rate changes observed in an iron ore concentrator were due to variations in particle shape. It was confirmed that ores mined from different locations differed in filtration rates by as much as 60%. However, when image analysis was used to quantify the shapes of the individual particles in the filtration feed, it was found that the particle shapes showed almost no variation, and the shapes did not correlate with the filtration rate. It was also determined that the filtration rate variations were not caused by changes in particle size distribution. These results suggest that the differences in filtration rate are due to factors other than size and shape, such as surface chemistry.

Jan 1, 2008

By B. Spigarelli

Carbon dioxide sequestration by conversion to carbonates has become a promising option for CO2 storage. Experiments were conducted to determine the feasibility of CO2 sequestration at ambient conditions using a Ca-rich industrial waste in a carbonate solution. The Ca-rich industrial waste used in this study was lignite fly ash. Fly ash was chosen because it is cheap, available near large CO2 point sources, already in powder form, and reactive due to amorphous properties. In the experimental set-up, CO2 absorption was inferred by monitoring feed and exhaust gas CO2 concentrations. The addition of an alkali to a fly ash-distilled water solution provided a 50% increase in CO2 absorption of the solution. Absorption time also increased by 50% compared to a fly ash-distilled water solution. TGA analysis was used to determine the extent of CO2 sequestration in the carbonate form. At a liquid to solid ratio of 20:1, the conversion of ?free? calcium to carbonates was 75%. A CO2 balance on the system concluded that at the current operating conditions 42% of the total CO2 fed to the system was sequestered in the carbonate form. SEM-EDS analysis of the fly ash particles before and after reaction with CO2 indicated that the carbonate compound being formed was calcium carbonate. The analysis identified rhomboidal structures on the surface of the fly ash particles after reaction with CO2, but not before. These rhomboids are characteristic of calcium carbonate formation and they had higher Ca, C, and O concentrations than the host spheres, suggesting calcium carbonate formation.

Jan 1, 2012

By D. F. Machuca-Mory

A change of support model consists of a procedure to change a stationary histogram at a small data scale to represent a larger scale; typically a distribution of sample drill-hole data is changed to represent a chosen selective mining unit (SMU) scale. Most grade variables average arithmetically. Thus, the mean stays the same for different scales, and the variance changes according to well-established theory using average variogram values. The longstanding challenge has been to predict how the shape of the histogram changes. The discrete gaussian model is widely used because it appears reasonable and introduces few artifacts; there are no artificial minimum/maximum values and the target mean and variance are reproduced exactly. The resulting distribution shape, however, is strongly dependent on a multivariate gaussian distribution. The authors generalize the approach by taking advantage of a property of the isofactorial model, which allows one to specify where the random function falls on the spectrum between a low-entropy mosaic model and a maximum-entropy diffusion model. A measure of dissemination (MD) is computed using a ratio of the madogram and the variogram. The change of support algorithm is developed that uses a variable measure of dissemination (VMD) that is easily calculated and fit to data from the deposit. The resulting VMD change of support model is very flexible to represent different mineralization styles encountered in practice; global predictions of recoverable reserves are more accurate and decision-making is improved. A number of real examples are shown to demonstrate the approach.

Jan 1, 2008

By David Hake, David Salisbury

The Drainage Services Department (DSD) of the Hong Kong SAR Government commissioned the design and construction of the West Kowloon Drainage Improvement, Stage 2, Phase 2, Kai Tak Transfer Scheme (KTTS) project in 2000 to relieve potential flooding in Mong Kok caused by the insufficient capacity of the existing storm water drainage system. The KTTS involves construction of a 1.5km,4.4m drainage tunnel and a 450m long box culvert, running from Waterloo Road near Hereford Road to the existing Kai Tak Nullah in San Po Kong. This paper describes the design and construction of; the bored tunnel through both hard rock and soft ground using a slurry Tunnel Boring Machine (TBM), six associated access shafts, a connection structure at Waterloo Road and the box culvert connecting the bored tunnel to the outfall at Kai Tak nullah. Details will be provided on the contractor’s alternative designs adopted during the contract including the use of fibre reinforced shotcrete as one-pass temporary and permanent support for three of the shafts and modifications to the Engineer’s design for the box culvert structure.

Jan 1, 2005

By R. Kaushik

According to the U.S Department of Energy (DOE), mineral processing activities including comminution (size reduction) uses 4% of the world electrical energy consumption. Such numbers reinforce the need to invest in energy savings initiatives in order to produce more using less. ENERGY EFFICIENCY OPPORTUNITIES AND CHALLENGES IN MINING OPERATIONS In addition, DOE, in its Mining Industry Energy Bandwidth Study, has identified huge potential for energy savings for the coal, metals and mineral industries. Even knowing the overall causes of energy waste and some potential tools for remediation, mining companies may struggle to apply such tools and get the desired results due to the following reasons: ? Limited staff ? Lack of accurate economic and investment analysis to justify energy savings projects ? Lack of knowledge to identify low or no-cost savings opportunities ? Internal competition for resources According to the workforce and talent management experts, the Talent Strategy Advisors, the demand for mining engineers is expected to exceed supply by 30% by 2013. Mining personnel are likely to be burdened with increasing and varied workloads with limited training. This will result in the need for automated and simple tools to support energy efficiency activities. Mining engineers will simply not have the time and resources to create such tools, collect and analyze the data to make decisions, and track results.

Feb 27, 2013

By John A. Breslin

The year 2010 will mark the 100th anniversary of the beginning of the research efforts by the U.S. government to improve the health and safety of miners working in the United States. This research began in 1910 with the establishment of the U.S. Bureau of Mines (the Bureau) and it has continued during the past 10 decades, even after the closure of the Bureau in 1996. The research on safer mining technology, formerly done by the Bureau, has now been combined with National Institute for Occupational Safety and Health (NIOSH) studies of miners? health to form a unified federal research program to improve the health and safety of miners. This article describes this research and places some of the accomplishments into perspective with other activities in the U.S. Mine Safety and Health Time Line (insert).

Jan 1, 2010

By William R. Yernberg

The 2003 Rapid Excavation and Tunneling Conference (RETC) was held at the New Orleans Marriott, New Orleans, LA, June 15-18. The New Orleans conference was the 16th since the RETC was formed in 1971. This year’s conference was sponsored by the Society for Mining, Metallurgy, and Exploration, Inc.(SME), with co-sponsorship of the Construction Institute of ASCE. Attendance at the meeting was 1,178, a conference record. This was up significantly from the771 attendees at the 2001 meeting in San Diego, CA. The RETC was formed to “advance the engineering and scientific knowledge of rapid underground excavation and tunneling through interdisciplinary meetings, publications, technical-educational exhibitions and encouragement of research.” The RETC conferences are now held every other year. They provide an opportunity for individuals to meet with designers, contractors and manufacturers associated with the tunneling industry to share experiences in all phases of tunnel design and construction.

Jan 1, 2003

By C. D. Ashley, X. P. Garzon-Villalba, R. M. Lopez, T. E. Bernard

Federal standards for refuge alternatives (RAs) mandate that they not exceed a Steadman apparent temperature (AT) of 95 °F (35 °C) at an assumedmetabolic rate of 325W, a limit that appears to be arbitrary. Occupants in an RA spend most of their time at rest (a metabolic rate less than 325 W), and thermal equilibrium can likely be maintained at an AT > 35 °C. The purpose of this study was to examine the upper limit of sustainable heat stress during 4- and 8-h exposures at rest. Five men underwent five 4-h trials (phase 1: AT range 39 to 49 °C, 90% rh) and five 8-h trials (phase 2: AT range 46 to 56 °C, 90% rh) in a semi-recumbent position. Descriptive statistics for gastrointestinal temperature (Tgi), heart rate (HR), systolic and diastolic blood pressure (SBP and DBP), sweat rate, fluid intake, urine color, urine specific gravity (USG), and changes in body mass are reported. Mean Tgi for all trials ranged from 36.9 to 37.3 °C, and mean HR for all trials ranged from 61 to 75 bpm. To determine the effects of increased heat exposure, differences in heat strain between 4- and 8-h trials were examined via repeated measures analysis of variance (ANOVA). As AT increased, there were no significant changes in ?Tgi and ?HR from 1 to 4 h in the 4-h and 8-h trials. During the 8-h trials, as AT increased, there was a difference in ?Tgi between 4 and 8 h. In conclusion, there was support for sustainable exposures resulting in no significant increase in physiological strain at an AT greater than 35 °C AT, with a sustainable limit (no increases in Tgi due to increases in AT) below 46 °C AT. Although the participants were not representative of coal miners, the results provide support for sustainable exposures greater than 35 °C AT at an average metabolic rate of 155 W.

Nov 8, 2019

Barrick Gold plans to have four new gold mines in production by 2006. Together, the mines would increase the company’s output by 40 percent. The projects include Veladero in Argentina, Alto Chicama in Peru, Cowal in Australia and Tulawaka in Tanzania. All of them are scheduled to begin production between the first quarter of 2005 and the first quarter of 2006. They are expected to drive Barrick Gold’s growth profile to a target of 211.5 to 217.7 t (6.8 million to 7 mil-lion oz) of gold production in 2007. The company’s projected output for 2004 is 152.4 to 155.5 t (4.9 million to 5million oz) in 2004. Overall, higher production and lower costs are expected in the early years from the new mines.

Jan 1, 2004

By T. McCallum

Crud is a common concern in SX processes and is formed as a complex solid stabilized emulsion of aqueous and organic.1,3 Crud formation is highly dependent on the amount of solids entering the circuit and is influenced by a number of other operational factors. A common practice for crud processing is interfacial pumping, wherein crud, organic, and aqueous are pumped from the settlers for treatment and utilizes a variety of equipment. These mechanical means of crud processing are effective, however, require significant processing time and require oversight to prevent the return of contaminated organic. Cytec has developed a unique crud treatment process utilizing both chemical and mechanical means to enhance the solid/liquid separation. The use of ACORGA CB? 1000 crud busting reagent allows a rapid separation of solids from the organic phase and provides similar volume recovery to current practices. The process allows operations to return clean organic back to the plant more efficiently and may enable operations to process more crud. In addition, the organic quality of the recovered organic is higher than that recovered by typical means, which can lead to operational cost savings.

Feb 27, 2013

By J. D. Miller, C. L. Lin

Appropriate software and hardware necessary to adapt a x-ray CT analyzer for determination of coal washability has recently been developed and sucessfully tested for well characterized samples under laboratory conditions. Evaluation of the CT-based analyzer under simulated on-line conditions is also presented to verify the on-line capabilities of the newly developed x-ray CT analyzer for the control of coarse coal cleaning circuits. The investigation shows that the data obtained from CT washability analyses compare favorably with experimental sink-float data. Further, image frequency was considered to evaluate the CT-Based coal washability analyzer for simulated on-line conditions. Specifically the number of observations (image spacing) needed for accurate sampling and the total time required to perform the calculations for a representative data set were determined.

Jan 1, 2001

By J. E. Friant

The Mini-DiscTM cutter drill bit is a radical design departure from the traditional tri-cone rockdrill bit. Miniature disc type cutting tools as small as 3.25 inches (82.5 mm) diameter are fitted to a bit body to cut individual concentric kerfs. The action is the same as that commonly used on large tunnel boring machines but miniaturized. The high performance rate and efficiency of a disc cutter are the result of producing a large proportion rock chips rather than sand or powder. The Mini-DiscTM drill bit, referred to as the “Disc Bit” has other unique features as well. It can be re-greased between runs. It can be rebuilt in the field in about 15 minutes, cutters can be replaced and the Disc-Bit appears to require less down hole hydraulic power than conventional bits. Thoroughly tested in the laboratory, the bit has recently been undergoing field trials in well drilling, blast hole drilling and shaft drilling. As any engineer knows, the laboratory can not shake out all the problems but it eliminates the more glaring weaknesses. Performance results have been exhilarating, and a few mechanical problems were discovered and largely overcome. This paper is a progress report.

Jan 1, 1999

By Christian Wawrzyniak

An analysis method for modeling compensation grouting based on the finite element method is presented. By this method the design parameters of compensation grouting, grouting pressure and grouting volume, can be evaluated. Also the subsidence of a building due to tunnel driving as well as the lifting of the building by compensation grouting can be simulated. The stress changes in the tunnel lining and in the foundation of the building are computed as well. The application of the analysis method is demonstrated on two examples for compensation grouting in combination with construction of tunnels.

By Lloyd M. English

During the past 30 years, the research arena has changed significantly in all fields, mining included. The relative representation of the topics of research, how the research is performed and who has performed the research have all changed. Although there are a lot of subjective ideas and anecdotal "analyses" concerning these changes, there has been no actual study of these trends to verify the facts. This study was divided into six five-¬year periods for the purposes of comparison. Some of the trends analyzed are co-authorship, research areas, research sponsors and cooperative efforts. In today's research arena, 30 years is a long time. Technology has advanced more rapidly than in any time previously and that pace continues to increase. There are more researchers, more tools for research and an increasing number of companies, agencies and institutions engaged in research. The pace of change and its impact is often discussed and debated at professional meetings and in institutions that engage in research. These conversations will often influence the research decisions of the participants in directions to take or subjects to pursue.

Jan 1, 1995

By T. W. Peglas, J. Doherty, R. A. Day

The South East Transit Project is a $520 million project in Brisbane, Australia which includes the construction of a 32 km Busway to access the south-eastern suburbs. Close to the centre of Brisbane, tunneling techniques have been used to minimise surface disruption. This paper describes some of the features of the longest driven tunnel on the project, the Vulture Street Tunnel. The Busway is a two lane expressway for buses which requires a 10.2 m finished width and a 12.6 m excavated span of driven tunnel. The Vulture Street Tunnel carries the Busway at minimal cover beneath the operating Vulture Street Railway Station, beneath a three storey office building and beneath the roadway to the Mater Hill Busway station. Halfway along the route, a Y-junction has been constructed to enable future connection with a light rail route. Key features in the design and construction of the Vulture Street Tunnel include: Use of canopy tubes to drive a 12 m wide tunnel beneath operating railway tracks with less than two metres of cover in highly weathered rock. Underpinning the office building in the route of the tunnel construction from within the building carpark. Construction of a 24 m span Y-junction with 7 metres cover of weathered and faulted rock. Use of predictive analysis as an adjunct to traditional back analysis to estimate the tunnel settlements from pressuremeter test results. This paper describes the design methodology with particular reference to settlement prediction, as well as construction innovations used to complete the tunnel. This paper will be of interest to all designers who have to create large spans in minimal cover in weak rock in urban areas and who have to predict the settlement

Jan 1, 2001

By A. Dale Wunderlich

Since Sept. 11, 2001, the author has been asked by several mining companies and mining publications to share some of his insights on how the terrorist attacks on the World Trade Center (WTC) and Pentagon might affect the mining industry globally. Until now, the author has been reluctant to express his thoughts in a publication that could possibly fall into the hands of terrorists and give them some ideas that they may not have been previously considering. However, the author discussed the contents of this article with several friends and acquaintances in the international intelligence community. They said that nothing commented on here is new to the terrorists. Potential terrorist targets Sources within the worldwide intelligence gathering community have told the author that current intelligence data indicates that it is likely that the Islamic fundamentalist groups responsible for the attacks on Sept. 11, 2001will likely be directing their effort at foreign business entities. Any overseas or any domestic businesses of highly visible companies that are part of the anti-terrorism alliance should consider themselves a potential target.

Jan 1, 2002

By Kerry Lahti, Bryan Ulrich

On Feb. 11, 2005, more than 20 mining professionals gathered in Elko, NV for a day-long round-table discussion on heap leaching. Attendees included project managers, operators and environmental professionals. They represented 10 mining organizations. Knight Piésold sponsored the special event. Its seven representatives included three staff members from the company’s Elko Operation, and one each from its Denver, Cajamarca (Peru) and Vancouver offices. The roundtable format was chosen to allow people from the mining industry to share ideas and experiences in an open forum. Rather than presenting prepared talks, spontaneity was encouraged. This resulted in a lively and enjoyable discussion.

Jan 1, 2005

By Gordon M. Matheson

The factors which control chimney subsidence sinkhole development in weak rock were assessed by analyzing the characteristics of approximately 3000 chimney subsidence features along the Colorado Front Range. The area of study included features developed over abandoned mines in the Colorado Springs Coal Field, the Boulder Coal Field, and the Foothills District. The approximate locations of the areas studied are shown in Figure 1. Data were collected for sinkholes occurring over both room and pillar, and retreat mining areas in coal seams with a wide range of dips. The location, size, and approximate time of development of each sinkhole were documented. From these data, relationships were developed which describe the time rate of observable sinkhole development and the relative location of sinkhole development with respect to mined height, overburden thickness, and type of mining for relatively flat-lying coal seams. In addition, the observed locations of sinkhole development over steeply dipping coal seams were assessed for portions of the study area.

Jan 1, 1986