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By H. Walqui

This paper describes operating gains resulting from standardizing operating and maintenance practices to improve the performance of the pebble crushing circuit at he Empire Concentrator. Past efforts have led to improved operating time but no additional throughput gains. New Operating standards and checklists were developed and introduced. The content and frequency of the review process indicators was then changed to take advantage of the new practices resulting in an increased feed rate and availability through the pebble crushing circuit.

Feb 27, 2013

By Yosry A. Attia

One of the most significant advances in Mineral Processing in recent years, is the development of the selective flocculation technology. The technology is primarily aimed at recovering the mineral values from ultrafine ore suspensions. This is achieved by selectively aggregating the mineral particles in question to such size as to enable their effective separation from the suspension. Selective flocculation utilizes the differences in the physical-chemical properties of the various mineral components in the mixed suspension. It is based on the preferential ad- sorption of an organic flocculant on the particular solids to be flocculated, leaving the remainder of the particles in suspension. In order to understand the mechanics of this process, selective flocculation may be divided into four major sub processes; these being: ore slurry dispersion, in which all the particles are stably and uniformly distributed in the suspension with the individual particles being essentially separate; flocculant selective adsorption and floc formation; floc conditioning, which aims at obtaining flocs with desire properties for their subsequent separation and with minimum entrapment of dispersed particles; and floc separation from the suspension. These sub processes will be reviewed later in this article.

Jan 1, 1982

By William R. Yernberg

Most citizens take it for granted, but minerals produced in the mines of the western United States, including Colorado, are crucial to nation’s standard of living and quality of life, said Colorado’s Gov. Bill Owens in his welcoming remarks at the 106th National Western Mining Conference. The conference, which was organized by the Colorado Mining Association (CMA), was held Feb. 4-6, 2004, in Denver. Attendance was425, up substantially from last year’s meeting. The meeting included the CMA annual membership meeting as well as the CMA chairman’s and president’s reports. The meeting also included awards presentations in which companies were recognized for their efforts in pollution prevention, health and safety, and reclamation. The conference also included a tradeshow.

Jan 1, 2004

By D. J. Gilbert

As a preventive action, the geotechnical department at the mine analyzed the original topography overlying a conveyor tunnel at the mine. Several dewatering drains were installed to intercept water collecting from an old lakebed. Subsequently, 20 steel arches were installed to provide additional support in an area of tunnel where original geological mapping indicated Type IV rock. This project was completed ontime with no loss to production. Construction schedules had to be developed to half hour precision, to accommodate the installation.

Jan 1, 2011

By S. J. Schatzel, K. M. Ajayi, E. N. Rubinstein, Z. Khademian

This study simulates the impact of a shale gas well casing breach near a longwall mine. Field studies are conducted to measure mining-induced permeability changes over the abutment pillar of a longwall mine, and a geomechanical model is developed in 3DEC, a three-dimensional numerical modeling code, to predict the aperture of fractures in the overburden at the study site. The predicted aperture values are used to determine mining-induced permeabilities and the results are compared with the field measurements. These aperture values are provided as inputs into fracture flow code (FFC), which generates a stochastic discrete fracture network (DFN) model for the study site and predicts the potential shale gas flow to the mine. Results from 100 DFN realizations are statistically analyzed using the bootstrapping method to compensate for notable variation in fracture geometry. The results show a significant difference between the gas inflow for nearby panels due to increase in the induced permeability during mining of the second panel. The average gas flow to the mine was calculated as 4.72×10−2 m3/ s (49 cfm) for a hypothetical breach at the Sewickley horizon during the first panel mining, 8.97×10−3 m3/ s (19 cfm) for a hypothetical breach at the Uniontown horizon during the first panel mining, 2.16×10−1 m3/ s (458 cfm) for a hypothetical breach at the Sewickley horizon during the second panel mining, and 8.07×10−2 m3/ s (171 cfm) for a hypothetical breach at the Uniontown horizon during the second panel mining. Depending on the mine ventilation system, this could result in methane concentrations exceeding regulatory limits. Hence, these findings provide insights into the potential risk of an unconventional gas well casing breach near a longwall mine under shallow cover.

Feb 15, 2023

By J. A. Lombardi

Acid-Minesite-Solutions (AMS) are defined as copper-containing pit lake, tailing pond, acid-mine-drainage, and heap and waste dump irrigation solutions. All of these solutions are characterized by copper, acid and water contents that have value as individual commodities. HW Process Technologies, Inc. (HWPT) has developed nano- and hyper-filtration membrane methods for the separation of copper and other base metals, acid and water from AMS. These treatments are collectively called HWPT?s Engineered Membrane Separation® (EMS®) systems. The EMS® method of copper recovery produces small volumes of higher-concentration copper solution from large-volume, copper-dilute AMS. A case study of the 4,000 gpm Cananea EMS®-AMS plant for the recovery of copper from an acid-pit-lake resource is described. The EMS® method of copper removal from AMD and tails pond waters has been bench-scale demonstrated and are described, complete with projected budgetary capital and operating costs. Additional treatments for the recovery of sulfuric acid and high-quality water from the permeate (membrane passing) waters for the above-described AMS treatments are presented, with budgetary capital and operating cost estimates. [ ]

Jan 1, 2009

By S. P. Taite, A. R. Charest, P. D. Lewis

The El Sauzal deposit is a classic, high sulfidation, epithermal gold system located in southwestern Chihuahua State, Mexico. The prospect was discovered by a Francisco Gold Corp. geologist in1995. El Sauzal was encountered as a result of an extensive grass-root exploration program in the rugged, dissected volcanic terrains of the Sierra Madre Occidental, around the historical Batopilas Silver Camp. At El Sauzal, high grade gold is hosted within a series of more permeable, low-dipping, lithic and fine-grained dacitic rocks of early Tertiary age. The mineralization appears to be both structurally and lithologically controlled. The alteration characteristics are typical of a high sulfidation system including kaolinite, illite, alunite, dickite and pyrophyllite. The deposit’s gold distribution, as recorded from drill-hole data and surface samples, varies from 0.2 to 650.0 g/t. The estimated geological resource, as calculated from an independent study completed in 1998, was 3.0 million oz @ 2.03 g/t including a minable reserve of1.8 million oz @ 3.3 g/t.

Jan 1, 2004

By Jean-Michel M. Rendu

Increasingly, geologists use geostatistical methods to evaluate drilling programs. The complexity of the methods varies with the nature of the available sample information, the objective of the statistical analysis and the geologist's experience. Occasionally, estimating the average sample grade is all that is required. In other instances a semivariogram calculation may be considered. If sufficient data is available, the geologist may wish to estimate blocks or panels of complex shape, using the kriging method of evaluation. Historically, the use of geostatistics by geologists has been limited by a number of factors, most significant being the difficulty in accessing and using computer programs needed to complete the necessary studies. Geologists are often working in remote areas from which electronic communication is unreliable, if not impossible. Even when access to computer programs is technically possible, the costs incurred in accessing and using these programs are often considered prohibitive. In many instances using the programs requires an understanding of computer systems far beyond that which a field geologist can justifiably be interested in acquiring and maintaining.

Jan 1, 1984

By J. A. Organiscak

Water spray applications are one of the principal means of controlling airborne respirable dust in coal mines. Since many coals are hydrophobic and not easily wetted by water, wetting agents can be added to the spray water in an effort to improve coal wetting and assist with dust capture. In order to study wetting agent effects on coal dust capture, laboratory experiments were conducted with three wetting agents used by the coal industry on -325 mesh sized Pocahontas No. 3 coal dust. Significant differences in coal dust sinktimes were observed among the three wetting agents at water mixture concentrations of 0.05%, 0.1%, and 0.2%. The best wetting agent as identified by the coal dust sink test was only tested at the lowest 0.05% water mixture concentration and was found to have a negligible effect on spray airborne dust capture. Water spray airborne dust capture results for all three wetting agents tested at a 0.2% water mixture concentration showed that all three wetting agents exhibit similar but small improvements in dust capture efficiency as compared with water. These results indicate that the coal dust sink test may not be a good predictor for the capture of airborne dust. Additional research is needed to examine if the coal dust sink test is a better predictor of wetting agent dust suppression effects during cutting, loading, conveying, and dumping of coal products by comparison to airborne dust capture from sprays.

Feb 27, 2013

By Peter Loehr

Full-face tunnelling machines were introduced into German coal mines 12 years ago. It was aimed to utilize these highly efficient systems to drive mine tunnels in rock so that the large demand for development work in some mines could be met. A characteristic feature of coal deposits in Germany - and particularly in the Ruhr Area - is a thick overburden strata. Access is therefore only possible through vertical shafts. A network of horizontal drivages leading from these shafts open the deposits between the different mine levels. The hardcoal-bearing formations are multi-folded and heavily tectonically stressed. Apart from a few extensive fault zones there are many single faults of different natures in the carboniferous strata. During the course of decades coal mining has penetrated to ever increasing depths. Nowadays coal is mined from depths of between 600 m and 1,200 m. The effects of ground pressure in connection with extremely varying rock strengths and high temperatures are particular difficulties which have to be overcome during drivage work. The first full-face tunnelling machines to be applied in the mines had originally bee deigned and developed for tunnelling projects. Not only the machines themselves, but also the back-up equipment had to be adapted to meet the special demands of German coal mines.

Jan 1, 1983

By R. E. Scheffel

Most supergene copper heap leach operations today employ forced-aeration, irrespective of ore grade. Unfortunately, there is little published quantification of its benefit. There is a natural desire to strive for the ideal chemical kinetics. The reality, however, is that physical mechanisms control the commercial extraction rate. This paper presents the performance of a number of operations, their operating conditions and physical ore characteristics, which contribute to non-ideal solution distribution and variable extraction rate. Regardless whether one uses forced-aeration, commercial experience to date suggests it is prudent to design for longer leach cycle times to ensure the production target is met.

Jan 1, 2006

By Z. T. Mathe, M. A. Vera, M. C. Harris

This contribution presents a methodology how to quantify froth zone recovery in a continuously operated laboratory mechanical flotation cell. The methodology consists of relating the overall flotation rate constant to the froth depth of the flotation cell. As a result, a froth zone recovery factor (Rf) can be extracted. This froth performance parameter has been studied as a function of the flotation cell operating variables. By understanding the effect of these operating variables on Rf, an integrated methodology for modelling froth zone performance in batch and continuously operated laboratory flotation cells has been proposed. The Rf modelling is based on a semi-empirical approach which considers a number of parameters to be used. Some of these parameters may have physical significance, i. e. they may be easily and physically measured. The modelling approach consists of taking into account the interaction between the pulp and froth zones. This interaction allows froth zone recovery (Rf) to be predicted. The whole modelling exercise process lies on auxiliaries relationships which indicate the dependence of the parameters with the operating conditions of the flotation cell. This contribution is part of a larger project that deals with the modelling and optimisation of flotation plants (Project P9L, 2000).

Jan 1, 2001

By Robert M. Matyas, P. E. Sperry, Robert J. Smith, A. A. Mathews

INTRODUCTION The first Dispute Review Board (DRB) was utilized on a tunnel project 20 years ago. Increasingly utilized on a wide range of construction projects, DRB's are becoming the norm on tunnel and underground projects. This paper summarizes the growth in this usage, uses observations and experience to establish that barriers to the utilization of DRB's are more perceived than real and that many arguments against the DRB concept are not valid, and notes some of the salient elements that should be considered in practice to optimize DRB effectiveness. The purpose of the paper is to provide an annotated checklist for current and prospective users. The basic concept, structure, and operation of DRB's are described elsewhere and will not be repeated here (ASCE, 1991). DISPUTE REVIEW BOARD USAGE A compilation of Dispute Review Board usage for tunnel and underground projects to January 1994 indicated use on 63 contracts with a cumulative construction value of $3.8 billion and a total of 60 disputes settled. As of that same date, DRB's were planned for another 63 contracts with an estimated construction value of $4.7 billion. (A listing of these 126 projects is available from the authors.) This success and popularity have spread to other civil projects as well as process and building construction. The increase in DRB usage has been exponential. See Figure 1.

Jan 1, 1995

By I. A. Costa, Y. Fouquet, F. Barriga

"Lucky Strike and Menez Gwen are two hydrothermally active sites located along the border of the Azorean plateau, southwest of the Azores islands where the alteration processes affecting basaltic rocks are prominent (Costa et al., 2003). Here we report on a slabby brecciated rock, abundant at both Lucky Strike and Menez Gwen, composed mainly of basaltic fragments cemented by hydrothermal precipitates from warm fluid circulation system. Research reveals that hydrothermal alteration takes place mainly by replacement processes, in which silicification is dominant (Costa et al., 1997 and Costa, 2014).Petrographic observations, including scanning electron microscopy (SEM), microprobe analysis, and mass balance studies made on basaltic fragments within the breccia show that silicification is one of the main processes resulting from hydrothermal fluid circulation. This alteration process leads to complete replacement by silica, in extreme cases, forming an impermeable cap that may contribute to the formation of sub-seafloor sulphide deposits, including examples in the geological past."

Sep 1, 2014

By T. W. Beck

Drilling into coal mine roof strata to install roof bolts has the potential to release substantial quantities of respirable dust. Due to the proximity of drill holes to the breathing zone of roof bolting personnel, dusts escaping the holes and avoiding capture by the dust collection system pose a potential respiratory health risk. Controls are available to complement the typical dry vacuum collection system and minimize harmful exposures during the initial phase of drilling. This paper examines the use of a bit sleeve in combination with a dust hog-type bit to improve dust extraction during the critical initial phase of drilling. A twisted-body drill bit is also evaluated to determine the quantity of dust liberated by comparison to the dust hog-type bit. Based on these laboratory tests, the bit sleeve may reduce dust emissions by one-half during the initial phase of drilling before the drill bit is fully enclosed by the drill hole. Because collaring is responsible for the largest dust liberations, overall dust emissions can also be substantially reduced. The use of a twisted-body bit has minimal improvement on dust capture compared to the commonly used dust hog-type bit.

Feb 27, 2013

Many states rely upon the Pennsylvania 1957 “Gas Well Pillar Study” to evaluate the coal barrier surrounding gas wells (Commonwealth of Pennsylvania, 1957). The study included 77 gas well failure cases that occurred in the Pittsburgh and Freeport coal seams over a 25-year span. At the time, coal was mined using the room-and-pillar mining method with full or partial pillar recovery, and square or rectangle pillars surrounding the gas wells were left to protect the wells. The study provided guidelines for pillar sizes under different overburden depths up to 700 ft. The 1957 study has also been used to determine gas well pillar sizes in longwall mines since longwall mining began in the 1970s. The original study was developed for room-and-pillar mining and could be applied to gas wells in longwall chain pillars under shallow cover. However, under deep cover, severe deformations in gas wells have occurred in longwall chain pillars. Presently, with a better understanding of coal pillar mechanics, new insight into subsidence movements induced by retreat mining, and advances in numerical modeling, it has become both critically important and feasible to evaluate the adequacy of the 1957 study for longwall gas well pillars. In this paper, the data from the 1957 study is analyzed from a new perspective by considering various factors, including overburden depth, failure location, failure time, pillar safety factor (SF), and floor pressure. The pillar SF and floor pressure are calculated by considering abutment pressure induced by full pillar recovery. A statistical analysis is performed to find correlations between various factors and helps identify the most significant factors for the stability of gas wells influenced by retreat mining. Through analyzing the data from the 1957 study, the guidelines for gas well pillars in the 1957 study are evaluated for their adequacy for room-and-pillar mining and their applicability to longwall mining. Numerical modeling is used to model the stability of gas wells by quantifying the mining-induced stresses in gas well casings. Results of this study indicate that the guidelines in the 1957 study may be appropriate for pillars protecting conventional gas wells in both room-and-pillar mining and longwall mining under overburden depths up to 700 ft but may not be sufficient for protective pillars under deep cover. The current evaluation of the 1957 study provides not only insights about potential gas well failures caused by retreat mining but also implications for what critical considerations should be considered to protect gas wells in longwall mining.

Jul 28, 2020

By William J. Robinson

What is the cummulative rate of recovery of copper from a sulfide leach dump? This is one of the most frequently asked questions today. We, in the industry, ask it of each other when we meet; however, the technical answers may vary from "I don't know" to 'quite good" from people within the same company. Management also poses this question because it plays a vital role in our planning for future production. The answer is difficult because of the many variables between different operations such as physical construction of the dump, topography of the original site, characteristics of dump material, mineralization, water application, etc. Each has a bearing on the rate of recovery. OPERATIONAL DATA Our method of water distribution is unique in that each dump is drilled to allow physical injection of water into the dump. The in¬jection holes are drilled vertically, on 251 centers, from the surface of the dump. Normally, the holes are drilled 40' deep and cased with 4" PVC perforated pipe.. The pipe is perforated at one-foot intervals with four V diameter holes at 901 spacing on the pipe circumference. We formerly alternated shallow holes (20'-40') with deep holes (80'-l80') in an effort to cover the entire dump and hasten oxidation. The shallow hole depth varied according to the compaction thickness. The deep hole depth varied according to the height of the dump and the original ground profile, We prefer to have the deep holes end 20'-30' above the original ground level. This generally allows us to penetrate the coarse material at the bottom of the dump. We had to discontinue the deep holes_ in order to cover more dump area in a shorter period of time to meet increased production requirements.

Jan 1, 1972

Newmont Gold's methods for deposit modeling vary, depending on geology, mining and processing methods, economic feasibility and availability of historical information. It is argued that successful modeling requires understanding these factors, knowing the strengths and weaknesses of the various modeling techniques and being flexible in selecting the appropriate methods. Newmont is one of the world's largest gold mining companies, with operations in the United States, Peru, Mexico, Indonesia and Uzbekistan. And it is active in exploration worldwide. At the end of 1996, Newmont declared a total reserve of 1.15 equity kt (37.1 million equity oz) of gold and 2.17 equity Mt (2.39 million st) of copper. The gold deposits managed by Newmont totaled 752 Mt (829 million st) of ore containing 1.28 kt (41.3 million oz) of gold averaging 1.71 g/t (0.05 oz/st). In addition, Newmont is developing a porphyry copper-gold deposit that totals 9.1 Gt (1 billion st) of ore containing 380 t (12.1 million oz) of gold and 4.82 Mt (5.32 million st) of copper. (In May 1997, Newmont Gold Co. merged with Santa Fe Pacific Gold Corp., thus increasing Newmont's reserves to 1.72 kt or 55.2 million oz of gold and 2.17 Mt or 2.39 million st of copper.)

Jan 1, 1998

By D. H. Carlson, J. H. Johnson, C. F. Renders

Introduction Diesel-powered vehicles are used extensively in underground mines throughout North America. The bulk of the diesel vehicles found in underground mining operations are used for loading and ore haulage, as well as for transportation of personnel and supplies. Along with the advantages of using diesels underground is the disadvantage associated with diesel-tailpipe particulate-matter emissions (DPM). The concentration of DPM in the ambient air of US underground metal mines is not now regulated by the Federal Mine Safety and Health Administration (MSHA). However, recent studies have shown DPM to be mutagenic (National Institute of Occupational Safety and Health, 1988), and the American Conference of Governmental Industrial Hygienists (ACGIH) has recommended that the exposures of per¬sonnel to DPM be limited to an 8-hr time-weighted average concentration (threshold limit value or TLV) of 0.15 mg/m3 (Anon., 1995). The authors, while making measurements in a number of US underground mines that use diesel haulage equipment, found mine air DPM concentrations ranging from 0.2 to 2.36 Mg/M3 (McCawley and Cocalis, 1986; Watts et al., 1989; Cantrell et al., 1991; Haney, 1992; US Bureau of Mines, 1992; Watts, 1992; Watts et al., 1995). If the proposed DPM TLV were to be adopted as a permissible exposure limit (PEL) for US underground mines, the proposed limit of 0.15 mg/m3 PEL would be lower than any of the concentrations measured in the earlier studies and would represent more than a 15-fold reduction from the maximum 2.36 mg/m3 concentration. A 0.15 mg/m3 PEL would also represent a 4.5-fold reduction from the average 0.68 mg/m3 measured mine ambient air DPM concentration reported in this paper. Other diesel tailpipe emissions that are now regulated underground include carbon monoxide (CO), with a PEL of 50 ppm; nitrogen dioxide (NO,), with a PEL of 5 ppm; nitric oxide (NO), with a PEL of 25 ppm; and sulfur dioxide (SO,) with a PEL of 5 ppm. Because the concentrations of these gaseous pollutants and DPM are affected by the state-of-maintenance (Waytulonis,1992), it is important that a means be developed to measure emissions from engines that are now in service to determine when maintenance is needed. The current study was the result of an inquiry by mine¬maintenance personnel who had been receiving complaints about high concentrations of diesel soot (DPM) in mine headings from load-haul-dump (LHD) vehicle operators. Mine-maintenance personnel were searching for an objective test to determine if the diesel tailpipe particulate emitted was excessive. The mine was also evaluating electronically controlled, two-cycle, naturally aspirated, direct-injection diesel engines on some of their JCI (John-Clark Inc.) load-haul-dump (LHD) vehicles. These LHD vehicles were used to haul freshly blasted ore from mine headings to a feeder breaker. The feeder breaker breaks down the larger chunks and feeds the broken ore onto a conveyor. Michigan Technological University, in past studies, developed an emissions-measurement apparatus (EMA) ca¬pable of measuring diesel vehicle tailpipe pollutant concentrations (Chan et al., 1992; Chan et al., 1993; Carlson et al., 1994). At the time of the study reported here, most of the mine's LHD vehicles used a 12-cylinder, four-cycle, naturally aspirated prechamber diesel engine. The study was undertaken in cooperation with mine maintenance supervisors from late 1992 through July 1993. The objectives were to compare diesel exhaust emissions between the 6-cylinder, two-cycle, electronically controlled, direct-injected diesel engine and the 12-cylinder, four-cycle, prechamber diesel engine and to, then, use the data collected, in conjunction with mine ambient air measurements, to demonstrate the application of the "deterioration factor" (Chan et al., 1992), which is a measure of the state-of-maintenance of mine-vehicle engines that are now in service. The information would be used to identify vehicles that need maintenance to reduce emissions. The data reported here are unique in the sense that they combine underground diesel vehicle ambient and tailpipe

Jan 1, 1999

By S. Addie

In the early 1990’s the British Columbia (Canada) mineral industry frequently discussed the need to participate in, and compromise with, public environmental interests in order to ascertain long-term stability. However, as the decade progressed the mineral industry withdrew from almost all meaningful public participation. As government protected areas policy in the past year has illuminated, there is a continued need for long-term land access stability. This paper historically analyses the public engagement policies of the British Columbian mineral industry while it participated in long-term consensus-based multi-stakeholder land-use planning processes. From this analysis the paper recommends that the mineral industry reengage the public and institute a new working relationship with environmental advocacy groups so as to ensure British Columbia becomes the most sustainable mineral producing jurisdiction in the world.

Jan 1, 2011