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By F. D. Mendes, A. H. Martins

The high copper grade in the Igarapé Bahia (Brazil) gold-copper ore restricts the direct application of the classical cyanidation process. Copper oxide and sulfide minerals react with cyanides in solution, causing high leach-reagent consumption, raising processing costs and decreasing gold recovery. According to studies, a feasible solution would be to pretreat the ore to remove copper minerals prior to cyanidation. The goal of this experimental work was to study the conditions for the removal of copper from the Igarapé Bahia gold-copper ore by sulfuric acid leaching, applying a statistical approach to the experimental design. By using the Plackett Burman method, it was possible to select the variables that exhibited the largest influence on copper extraction at the sulfuric acid leaching stage. These variables were leach solution temperature, stirring speed, sulfuric acid concentration in the leach solution and ore particle size. The individual effect of these variables and their interaction influences on the experimental response were analyzed by applying the replicated full-factorial design method. Finally, the selected variables were optimized by the ascending-path statistical method, which determined the best leach experimental conditions for maximum copper extraction. The optimized leaching conditions resulted in a copper extraction of 75.5%. Keywords: Copper, Gold, Extraction, Sulfuric leaching, Optimization

Jan 1, 2003

By Robert A. Haney, Scott G. Vail, Kenneth G. Fields

The Mine Safety and Health Administration, in cooperation with IMC Global Operations, Inc., conducted a joint study to determine the effectiveness of the technology currently in use at the mine to control diesel particulate exposures. IMC Global operates an underground potash mine using diesel-powered equipment to extract minerals. IMC uses a variety of technologies to control worker exposures to diesel particulate. These technologies include: ventilation, low sulfur fuel, oxidation catalytic converters (OCC), maintenance and work practices. The study was conducted over a two-week period, two shifts per day. During the first week (six shifts), baseline data on exposures and diesel particulate emissions were obtained. New OCC's were installed over the weekend on all equipment on the test section. During the second week (six shifts), data were collected to assess the effectiveness of the new OCC devices. In addition to exposure and diesel particulate emissions data, mine ventilation, engine exhaust temperatures and mine operational data were obtained. The primary means of determining diesel particulate concentrations was the respirable combustible dust (RCD) method. Gas concentrations carbon monoxide (CO), carbon dioxide (CO,), and nitrogen dioxide (NO,) were measured using passive dosimeter badges and gas bottles. Results of measurements of diesel particulate, gases, and air- flows were analyzed to determine the effectiveness of airflow and oxidation catalytic converters for controlling diesel particulate exposures. The use of oxidation catalytic converters resulted in reductions of both workers' exposures and diesel emissions.

Jan 1, 1997

Traditional fine-grinding mills in mineral processing rely on the use of steel medium for particle size reduction. The IsaMill (a horizontal stirred mill with a 3, 000-L net chamber volume and a rated motor power of 1,120 kW) has successfully adopted a novel product-separator design, which has led to a major revision of medium use in fine grinding. The IsaMill separator has successfully operated with a wide variety of medium types, such as silica sands, river gravel, smelter slag, run-of-mine ore fractions and steel shots, with sizes ranging from 0.5 to 10 mm. Great flexibility in the IsaMill operations has been achieved for processing feed as coarse as 120 µm to a product as fine as 5 µm. This paper discusses the performance of two inert grinding media in the IsaMills that are used at Mount Isa Mines Ltd. for the processing of galena- and sphaleritebearing ores to below 10 µm. They are the copper reverberatory furnace slag (CRFS) and the heavy-medium plant rejects (HMPR). A methodology was also demonstrated for comparing the medium performance and for scaling up the IsaMills from a 1.5-L laboratory batch mill to a full-scale 3,000-L mill.

Jan 1, 2002

By Jorge Gutierrez C.

CODELCO-CHILE, the world's largest copper producer, began an integrated study of the informatics situation in the corporation at the end of 1980. As a result, a five years strategic Systems Plan was elaborated and approved by top Corporate management. Main points in this plan were: a systems architecture with information integration to the top level management; a higher degree of information technology in the production areas, an optional systems development resources utilization and a high profitability of the plan itself. During the study phase a series of theoretical definitions were fixed and used as a basis for the plan's design. A "common systems" approach was chosen as the development strategy instead of corporate systems or separate divisional efforts. Top management should be highly involved in the revisions of the plan, as well as qualified users should be chosen as project managers. The systems architecture should grant the information integration to the corporate level, in order to support an integrated planning and administration environment for the corporation. A total of 15 projects were defined, involving 570,000 man-hours and shifting the development efforts towards the production and production services areas. The paper presents a critical evaluation of the whole process, showing its good and bad aspects and a positive global balance. It also points some suggestions and hints to any corporation who wishes to get involved in a similar experience.

Jan 1, 1989

By M. Polat, G. Ahuja, S. Chander, M. S. Klima

A study was conducted to investigate the use of flotation in combination with dense-medium cycloning utilizing ultrafine (-10 um) magnetite, as an integrated process for high-efficiency cleaning of fine coal. The objective was to produce a high-quality (low-ash, low-sulfur) coal, while reducing the amount of non-magnetic material that would need to be removed by magnetic separation. Three dense-medium cyclone tests were performed using different underflow diameters to produce feed material for the flotation separations The use of different underflow configurations caused a variation in the pulp and solids splits, which changed the clean-coal yield and the magnetite-to-coal ratio of the cyclone products, and hence, the composition of the flotation feed. Flotation was used to separate the clean coal and to recover the magnetite contained in the cyclone overflow stream. Any ultrafine refuse material, which may have reported to the cyclone overflow stream, was also removed in this step, further upgrading the product. In addition, flotation was used to improve the overall yield by recovering a middlings fraction from the cyclone underflow stream. It was found that flotation was very effective in separating the coal (or middlings) from the ultrafine magnetite, even under variable feed conditions. Magnetite recoveries approaching 99% were possible using rougher-cleaner separations in a laboratory flotation cell. This paper presents the results from this study.

Jan 1, 1995

By Nico Bezuidenhout, André M. van Niekerk, Jan J. G. Vermaak

This paper documents empirical evaluations of geochemical data that was recorded during a seven year pilot scale experiment. The experiment was aimed at assessing the effectiveness of natural soil covers for rehabilitation of coal discard facilities. Ten test cells were constructed using different natural soil cover materials and configurations. Results of the evaluation indicate that, although a pH breakthrough was not recorded for the single layer soil cover cells as was the case with the uncovered cells, single soil covers were not effective in preventing ARD oxidation processes. Multi layered soil covers were found to be able to create anaerobic conditions leading to a reduction in ARD oxidation processes and an improvement in leachate quality.

Jan 1, 2000

By Bruce S. Brown, Jeremy P. Haile

The construction of tailings facilities and heap leach pads for gold mining operations generally requires the installation of one or more impermeable liners beneath the structures to satisfy environmental regulations and prevent the leakage of gold bearing solutions. Liners are usually constructed using clay soils or synthetic membranes, such as high density polyethelene. Low permeability soil liners can be constructed from natural clays, well graded soils with only a small clay content, or sandy soils blended with a small quantity of imported clay such as bentonite or kaolinite. The permeability of such materials, prgperly pped with good quality control, generally lies in the range of 10- to 10- cm/s, and can be designed to meet minimum prescriptive standards set by regulatory agencies. Important benefits resulting from the use of clay liners include the slow rate of penetration of a saturated wetting front, the decrease in permeability of the liner as it consolidates under the applied load of tailings or ore, and attenuation of potential contaminants in the process solutions. Synthetic liners can be attributed a finite permeability as a result of minute perforations and seaming deficiencies, and possess none of the above properties. Synthetic liners are also, by their nature, relatively thin and even a small head build-up above the liner will result in a large hydraulic gradient across it.

Jan 1, 1988

By J. A. Chermak, D. D. Runnells

Sulfide-bearing waste rock, ore and tailings have the potential for generating acid rock drainage (ARD) when exposed to an oxidizing environment. The possibility exists of utilizing the acid produced to react with lime and/or limestone to form a self-sealing cap on the reactive waste rock and tailings. Laboratory column experiments were conducted using acid-generating waste rock with a surface amendment of limestone and/or lime. Artificial rainwater was introduced and allowed to drain through the columns. Results demonstrated that the limestone and lime reacted with the acidic rock, resulting in the precipitation of a hardpan layer of gypsum and amorphous iron oxyhydroxide at the surface. The hardpan layer significantly reduced the effective permeability of the column. Based on the results of this study, it should be possible to create hardpan layers as chemical caps to significantly reduce the infiltration of rainwater and snowmelt into acidic waste rock or tailings material in the field. Unlike traditional capping methods, e.g., clay and high-density polyethylene (HDPE) covers, chemical caps should be self-healing.

Jan 1, 1998

By R. Mohan Srivastava

In any operating mine, especially in precious metals operations, immediate improvements in profitability m readily achievable through more effective grade control. Just as the oil industry has come to recognize that enhanced oil recovery (EOR) in existing oil fields yields a higher return on investment than exploring for new oil, so too must the mining industry recognize the benefits of enhanced metal recovery (EMR). Current grade control practices are generally dismal. The very word "control" suggests a willingness to make the best of a bad situation -- as in "damage control" or "disease control" -- and a failure to perceive the opportunities for improved profit. While damage and disease can merely be controlled, success and improved profit can be engineered. This paper presents one approach to enhanced metal recovery. It shows how existing methods can be used to address the issue of ore/waste discrimination. The following sections outline the problem, describe the current state of the practice of grade control, propose an alternative approach and. illustrate the application of the proposed alternative to actual blasthole data from an operating gold mine.

Jan 1, 1992

By L. Shevenell

Nevada now has, or will have, 35 pit lakes resulting from open-pit mining below the water table. State regulators are requiring that the ultimate pit lake water quality be predicted as part of the permit application process. Water balances/pit lake filling rates must be esti¬mated in support of the geochemical modeling. In Nevada, analytical and numerical methods have been employed for the study of pit lakes. In the current work, analytical solutions are investigated for one pit lake, the Getchell south pit lake, which previously filled be¬tween 1968 and 1982 during a hiatus in mining. Water levels vs. time are available for this lake and these data have been fitted with a hyperbolic curve. This water-level-vs.-time curve was used in simple water-balance computations to find the net inflow rates by forcing computed water levels and volumes to match those of the known water levels and volumes through time. The model described here provides realistic volume fluxes into and out of the lake on a monthly basis as the pit lake filled.

Jan 1, 2000

By V. R. Degner

Given: the process tonnage, performance objectives, and plant floor area, the paper will outline the metallurgical and machine hydrodynamic scale-up procedures for translating the lab flotation test results to the design of a full size flotation machine installation, including the machine number, size, and arrangement. Machine selection considerations for rougher, scavenger and cleaner duty, and special considerations relative to specific applications, will be summarized where appropriate. The value of kinetic modeling in quantitative metallurgical (lab to full size machine) scale-up will be reviewed considering a coal installation, and design information for additional applications such as copper, molybdenum, iron, phosphate, and potash will be discussed.

Jan 1, 1986

By Etienne Simode

When a fire breaks out in a mine access road, the hot smoke, due to heat transfer with the surrounding strata, progressively cools as it moves forward. Depending upon the resulting temperature distribution, the density of the fluid changes. This change will bring about: Firstly, a variation in the resistance of the roads, a static factor which will affect ventilation flow rates; Secondly, the appearance of extensive aerodynamic driving loads in the vertical and angled roads, a dynamic factor which can have an extensive impact on ventilation. Because of the appearance of combustion and distillation products, the vaporization of water, which wets the timbering and strata, and the expansion of gases, fluid rates can at times be increased tenfold in the area of the fire. These disturbances may cause explosions and ventilation inversions, which fill other working areas with smoke toxic to workers, and which can come up upon rescue teams from behind. Due to the progressive heating of the surrounding rocks, which will slow down heat transfer, these dangerous conditions change over time. At the Lorraine Basin Coal Mines, programs have been set up and employed for the computer simulation of these phenomena over time. They serve to anticipate or to understand such phenomena, the input data being the characteristic parameters of the mine ventilation network, the operating curve of the main fans, and measurements or estimates of some temperatures. Two programs, employed together, have been developed for these studies: One program, called RESO, calculates the distribution of flow rates and pressures throughout the entire network; The other, called FEUMIN, determines smoke temperatures over their entire path.

Jan 1, 1980

By V. B. Achanti, A. W. Khair

This paper deals with the effects of various bit geometric parameters on the failure characteristics of rock material. Improving the rock-cutting efficiency of continuous mining machines has proven to be an interesting research topic during the last few decades. In the current study, an automated rotary rock-cutting simulator, duplicating a continuous miner, was used to study these parameters in the laboratory. The improvement of bit performance in terms of its life, cutting efficiency, dust production and energy consumption has drawn widespread attention. Research has demonstrated that optimizing bit parameters can result in efficient fragmentation of rock. Indiana limestone rock material was used in this study. The bit tip angle, bit tip size, bit spacing, depth of cut and cutting velocity of the rotary drum were varied to investigate the failure characteristics. The cutting pressure, penetrating pressure and the depth of cut were monitored on the simulator during the cutting process. Airborne dust and settled dust were measured for each experiment. Then, the specific airborne dust and specific energy were determined for each type of bit. Triaxial tests were carried out to correlate the failure angle of the rock in the static case to the dynamic cutting process failure. The physical and mechanical properties of the rock were also determined to assess their influence on the wear characteristics of each bit.

Jan 1, 2000

By Richard Stoltz, Gary Smith

This paper presents the findings of a face ventilation investigation, conducted by the Ventilation Division, Pittsburgh Health Technology Center, at a underground coal mine operating in the Illinois No. 5 coal seam. The purpose of the investigation was to evaluate the effectiveness of a blowing face ventilation system in controlling methane liberation in the face area while mining with brattice distances up to a maximum of 40 feet from the face (extended cut). The continuous miner on this section was remotely controlled and equipped with a machine mounted dust collector. Data collected during this investigation included methane concentrations, intake and return air quantities in the face area, and scrubber air quantities. In addition, a time study was conducted to correlate the methane peaks to activities in the face area. In conjunction with the face study on Section A, separate methane liberation studies were conducted on three additional sections: B, C, and D. This was done in order to compare intake methane concentrations and methane liberations from other sections in the mine to the test section. Calculations indicated that the minimum intake air quantity necessary at the inby end of the line brattice for the section investigated was 7,000 cfm. Due to the higher intake methane concentrations and average methane face liberations measured on three other sections, the minimum air quantities necessary at the inby end of the line brattice were determined to be 13,900 cfm, 11,100 cfm, and 15,000 cfm, respectively.

Jan 1, 1991

By Keith G. Wallace, Daniel J. Brunner

The traditional approach to mine ventilation planning involved making estimates of airflows, including leakage routes, and summing the corresponding pressure drops along consecutive paths in order to determine the fan pressures required. This methodology changed completely with the availability of computers. Mainframe digital computers began to be used for mine ventilation network analysis in the mid-1960's. Their use spread rapidly throughout the world in the 1970's. Mainframe machines were employed owing to the need for high speed numerical procedures and substantial storage requirements. However, during the past decade, the growing availability of low cost but powerful microcomputers has allowed the development of net- work analysis programs that can handle ventilation systems of hundreds of branches, and which can produce results within a few minutes. This paper discusses recent advances in software and hardware development specific to mine ventilation planning. Software developments include interactive data and output manipulation, graphical representation of output, internal checks on input parameters to preset ranges and subroutines which calculate the gas distribution throughout the network from known gas sources. Hardware advances have led to significant increases in memory to facilitate the analysis of large ventilation models, math co-processor chips which greatly shorten run times, and plotter hardware for graphical output displays. Recent software developments make it possible to graphically display output on printers faster than on standard plotters.

Jan 1, 1989

By R. L. Grayson, N. P. Reddy, D. A. Kinzler, S. Yuan, W. R. Myers, R. A. Wells

An examination was conducted on the impact of roof conditions and the mining cycle in determining a representative respirable mass concentration at the mid-shearer location on a longwall panel. Multiple personal gravimetric dust samplers, operated at a flow rate of 2.0 lpm, were used at different locations along the face to isolate the concentrations and variances associated with good and bad roof conditions under both the cutting and cleaning mode of operation. The number of samples needed to estimate the population variance at a given confidence level was analyzed. In addition, the statistical analysis showed that the coefficient of variation of dust concentrations at different locations and under different conditions ranged from 0.185 to 0.475, with an average value of 0.283. The estimates of the average dust concentration for a shift and the variance of the dust concentrations were calculated. A total of 48 data points were available for an [a x b] factorial ANOVA (analysis of variance). The estimates of the variance components were determined. The results from F-tests indicated that both the roof conditions and mining operations had a significant effect on the respirable dust concentration. There was no significant interaction effect between mining operations and roof conditions. In conclusion, this study shows that not only should sampling and analytical errors be considered in determining the required number of samples for a good estimate of the long-range exposures of miners, but also fluctuations of concentrations due to mining operations and geological conditions should be taken into account.

Jan 1, 1991

By John J. Reed

The 1945 fire at the Braden (El Teniente) Copper Mine in Chile took 354 lives, and ranks as the most lethal metal mine fire in history. The mine was developed in the wall of a canyon over 900 m (3,000 ft) deep. Principal entrance was through a main haulage adit at the canyon bottom, and up through two internal shafts. Mining was by block caving from the top of the orebody with most of about 900 men on shift working in three production areas. Ore was transferred by gravity to the haulage level through a complex system of ore passes with associated ladderways. Normal mine ventilation was incast through numerous level portals and up- cast through the shafts and raises. The fire was confined to a maintenance shop just inside the portal of the lower production level. Smoke, gases and flammable vapors were drawn into the mine, and a subsequent explosion of the gases destroyed an air door and injected carbon monoxide into the workings. Falling water in a drainage raise near the fire made it downcast, which carried gases down to all the lower levels where they were drawn into the levels and then up connecting raises. Miners attempting to escape by climbing down the ladderways from the production levels were met and killed by the rising gases.

Jan 1, 1989

By Steven A. Tesdahl

Maintenance means keeping equipment running or restoring it to operating condition. However, the 21st century will usher in a broader need for equipment management, a cradle-to-grave strategy to preserve equipment functions, avoid the consequences of failure and ensure the productive capacity of equipment. Profitable future mining operations will have reduced the 35% of operating costs typically spent on maintenance and the unfavorable impact of downtime that often multiplied these costs by 300%. They will survive those operations that tried to carry outdated "maintenance" thinking beyond the year 2000. These surviving operations will have applied modern management techniques, technology and information to align the efforts of people with the needs of equipment. Future managers will use equipment management as an integral part of an overall production strategy. They will see it as a means of raising productivity, improving performance and minimizing downtime to maximize profitability. This global thinking will characterize all operations planning to survive in the competitive world of mining of the next century.

Jan 1, 1998

By C. McLean, S. G. Kolb, A. J. Erickson, S. C. Moore

The Grossschloppen vein-uranium deposit, Bavaria, West Germany, was examined with underground workings during 1980-82 by Esso Erz GmbH, an affiliate of Exxon Minerals Company (EMC). Geologic evaluation entailed dense drilling of a portion of the deposit from workings constructed specifically for the program. Discovered in 1977, the deposit was initially explored by surface diamond drillholes which allowed definition of a 30-60 m wide vein system discontinuously mineralized along a 1000 m strike length and to at least a 450 m depth. The underground program was conceived as a cost-effective procedure to answer questions on vein correlation, grade continuity and variability. A 1200 m decline allowed access for detailed sampling of approximately 10% of the known area of mineralization. Fanned drillholes, logged by gamma probe, were spaced to provide intersections of veins at 10 to 20 m intervals. Six cross-cuts also penetrate the pitchblende and uranophane mineralization which occurs in 0.1 to 2.5 m thick quartz veins. Detailed cross-sections and level plans were constructed for resource estimates of the intensively studied portion of the vein system. The program resulted in the discovery of local, high grade areas and an average grade in the evaluated area nearly double that expected from surface drilling.

Jan 1, 1992

By Donald G. Wieland, James H. Meinholz

INTRODUCTION The Milwaukee, Wisconsin Metropolitan Area provides an ideal opportunity to review the advancement of the art and science of mixed face tunneling in the past 65 years. Although there were earlier tunnel projects in the Milwaukee area, by other agencies, the majority of those driven in the Twentieth Century have been done under contract with the Milwaukee Metropolitan Sewerage District through the agency of the Sewerage Commission of the City of Milwaukee and the Metropolitan Sewerage Commission of the County of Milwaukee. Legal Description of District The Milwaukee Metropolitan Sewerage District was created by the Wisconsin Legislature in 1921 together with the Metropolitan Sewerage Commission of the County of Milwaukee. This concept of subregional wastewater control was an outgrowth of an investigation and report from a commission appointed by the Common Council of the City of Milwaukee in 1909 to study final sewage disposal for the City. In 1911 that Commission, comprised of J. W. Alvord, George C. Whipple and Harrison P. Eddy, recommended that the City construct a water filtration plant, construct a Menomonee River flushing works, expand the intercepting sewer system and, after a thorough study of the then existing and developing methods of sewage treatment, construct a sewage treatment plant. In response to those recommendations, the Wisconsin Legislature, in Chapter 608 of the Laws of 1913, created the Sewerage Commission of the City of Milwaukee. Recognizing that the improvement of surface water quality would require action on a watershed basis, the Legislature, in Chapters 554 and 590. of the Laws of 1921, created the

Jan 1, 1979