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Semiautogenous (SAG) ball mills are being increasingly used today for the coarse grinding of a range of ores, including gold, copper and iron. Larger mines are demanding mills with larger throughputs. This has led to some remarkable developments in mill diameters and installed powers. Conventional design principles - mills with trunnion bearings - have reached their limitations. This article describes one SAG mill with a slide-shoe arrangement and Krupp Polysius' Combiflex twin drive. In August 1997, the world's largest SAG mill with a slide-shoe arrangement was commissioned in Queensland, Australia, operating as a wet mill. The inside diameter is 10.4 x 5.1 m (34 x 17 ft) effective grinding length. The 1.36-ktlh (1,500-stph) SAG mill is driven by two Combiflex drives (twin drives with 2 x 5,500-MW or 7,375-hp installed motor power) in conjunction with a girth gear (outside diameter 11,890 mm or 468 in.). Commissioning of the SAG mill was completed with no notable technical difficulties. The plant runs continuously except for planned maintenance stoppages and process-specific reasons. As this article is written, the machine has been in operation for about 8,000 hours without major problems.

Jan 1, 1998

By J. Bigu

Use has been made of several theoretical models to predict radiation levels in underground uranium mines. The models used are the Evans model, the Thomas-Epps mine model, the isolated mine model, the mine tunnel with no air flow and the mine tunnel with air flow (Beckman and Holub). Calculations based on the above models have been extended to include thoron gas and its progeny, a common occurrence in some Canadian uranium mines. Theoretical predictions include radon and thoron progenies WLs and concentrations, and some ratios of great practical interest. The main differences between the models are pointed out and comparison is made with experimental data gathered during the last three years in several Canadian underground uranium mines.

Jan 1, 1981

By K. Burke, G. Zhan, A. Mayer

A cover with capi1lary barrier effects (CCBE) is being constructed an the AA leach pad at the Barrick Goldstrike mine near Carlin, Nevada. The purpose of the cover is to eliminate/minimize infiltration of meteoric waters into the leach pad. Laboratory and numerical analyses indicate that Carlin Formation siltstone (TCS), a locally available material, has the necessary hydrologic characteristics when placed on the leach pad to act as a CCBE. A pilot study was conducted on a mall-scale test cover placed on the AA leach pad to examine the cover performance under irrigated conditions. The preliminary test results demonstrate that the designed cover is capable of preventing meteoric water infiltration.

Jan 1, 2002

By R. Q. Honaker, D. P. Patil, A. Sirkeci

Because of increasing production of fine coal during mining over the past century and because of inefficient fine-coal recovery technologies, a vast reserve of high-quality coal now exists in refuse ponds. A novel finecoal circuit, consisting of a hindered-bed classifier, an enhanced gravity concentrator and a flotation column, was evaluated for the recovery of fine coal from refuse ponds. The treatment of a pond derived from Pittsburgh No. 8 seam coal resulted in the production of a premium fuel containing less than 5% ash and a calorific value of about 30,170 kJ/kg with 60% mass yield. Results from the treatment of two refuse pond materials are presented in this paper.

Jan 1, 2002

By Mark R. Stanton, Douglas B. Yager

Integration and synthesis of mine-site topography, geophysical, and geochemical data yields both two- dimensional and three-Amensional perspective models for the May Day mine located in the Cement Creek drainage near Silverton, Colorado. Induced polarization, geophysical data are spatially registered with geochemical data acquired from drill hole cuttings that are contoured m three-dimensional space, thereby permitting determination of the most metalliferous and sulfur rich zones of a waste pile. This spatial modeling application was developed to be a visually intuitive tool to aid in mine waste reclamation.

Jan 1, 2000

By F. M. Doyle, K. Osseo-Asare, E. Peters

With the aid of molecular orbital theory, a discussion is presented of the relationship between the electronic structures of ions and molecules, and the elementary steps involved in homogeneous electron transfer reactions. An electronic theory of the reactivity of oxidants and the mechanism of action of oxidation catalysts is then presented, with emphasis on the oxidative decomposition of metal sulfides. For model oxidants, two molecular reagents: O2 and Cl2, and two ionic reagents: Fe3+ and CU2+ were selected; silver (1) was chosen as the model catalyst. The reactivities of these reagents are rationalized in terms of constraints on orbital overlap, the availability of unoccupied d orbitals, and the rearrangement of electronic configurations.

Jan 1, 1993

By Dirk van Zyl, Clint Strachan

A study was conducted to assess the feaeibility of increasing the heap height above one lift at the Alligator Ridge Mine. This study concentrated on the physical aspects of the heap and liner performance. Two principle aspects were addressed during this investigation: (a) the adequacy of heap permeability under present and future loading conditions; and (b) the adequacy of the liner to limit seepage losses. Field and laboratory test a were performed and their details and results are presented. It was concluded that the permeability of the heap would remain adequate for higher heap. The geometry of the heap will be the major constraint. It was also concluded that the liner would perform satisfactorily beneath higher heap.

Jan 1, 1987

By K. Hanumantha Rao, P. K. Sharma

A pure strain of Paenibacillus polymyxa and mineral- adapted strains are used to bring about surface chemical changes on pyrite and chalcopyrite and, thus, theirflotation. Paenibacillus polymyxa was adapted by repeated subculturing in the presence of pyrite and chalcopyrite. The surface chemical changes of bacteria due to adaptation and of minerals after their interaction with bacterial cultures are evaluated by electrokinetic and infrared spectroscopy and are discussed with reference to their flotation responses. Interaction of bacterial cells, bacterial metabolites and whole bacterial cultures affected the Hallirnondflotation behavior of the sulfide minerals. The Xanthate flotation results show that pyrite, but not chalcopyrite, is depressed when the tests are carried out after interaction with chalcopyrite-adapted Paenibacillus polymyxa. This investigation demonstrated that the surface chemical properties of bacteria can be manipulated successfully to achieve the desired effects in the flotation process.

Jan 1, 2000

By William H. Pomroy, Annie M. Carigiet

This U.S. Bureau of Mines report is an analysis of underground coal mine fire incidents occurring in the United States during the 15 years from 1978 through 1992. The fire data used in this analysis were obtained from Federal Mine Safety and Health Administration (MSHA) mine fire investigation reports. Fires were analyzed by year, state, coal bed thickness, mining method, evacuation measures taken, ignition source, burning substance, location, equipment involved, detection method, time of day, number of injuries and fatalities, and method of extinguishment. In all, 164 fires are reported, or an average of 10.8fires per year. The most common ignition source was electricity, the most common burning substance was coal, the most frequent fire location was the belt entry, belt conveyors were the most common equipment involved in fires, and water was the most common extinguishing agent.

Jan 1, 1995

By X. Cui, H. Ding, J. Wen, Q. Gu

This study is a continuation of previous work designed to further explore the mechanism of the bioleaching of sulfide concentrate at neutral pH by heterotrophic bacteria Bacillus megaterium QM B1551. The concentrate contained 13.2 percent nickel (Ni) and 0.2 percent cobalt (Co), which presented primarily as pentlandite and pyrrhotite. Contact and noncontact bioleaching experiments were conducted with finely ground ore at an initial pH of 6, resulting in 44.7 percent of Ni and 38.2 percent of Co leached in the contact-bioleaching treatment. Oxidation experiments of sulfur, thiosulfate (S2O32−) and ferrous ions (Fe2+) by cell membrane were performed to verify whether sulfur transferase, thiosulfate quinone reductase and enzyme cytochrome B558 on the surface of the bacteria could be expressed to oxidize the sulfide. The results show that thiosulfate quinone reductase and cytochrome B558 could be expressed to oxidize S2O32− and Fe2+ to SO42− and Fe3+, respectively.

By Stefan Zanon, Ty Faechner, Clayton V. Deutsch

Secondary data are important in geostatistical simulation of continuous variables. Geophysical data and geological trends are used for modeling porosity and permeability. Multiple mineral grades must often be modeled for mining applications. Sequential Gaussian simulation (SGS) is often used because of its relative simplicity and robustness. The two most common approaches to integrate secondary data in Gaussian simulation are with (1) locally varying mean, or (2) collocated cokriging. A significant problem with both of these techniques is variance inflation, that is, the variance of the resulting simulated values is too high because of an inappropriate decision of stationarity or an artifact of choosing a single secondary data in presence of many. We introduce a self-healing procedure for dynamic correction of this problem. The dynamic correction is different for the locally varying mean approach and for collocated cokriging since there are different reasons why each of these methods causes variance inflation. The reasons for variance inflation are discussed and the self-healing is applied to a number of data sets.

Jan 1, 2002

By John Waggoner, Steve Klein, John Townsend, Jay Arabshahi

The Riverside Badlands Tunnel is a 13 km (8 mile) long segment of the Inland Feeder Project. This 3.65 m (12 ft) finished diameter water tunnel presented many challenges that had to be overcome to take the project from concept to reality, not the least of which were the diverse ground conditions. Construction of the tunnel was carried out by a single tunnel boring machine (TBM) in one tunnel drive. The project is considered a success due to the accurate baseline established for the ground conditions; the approaches used to mitigate adverse conditions; and the appropriate use of TBM excavation methods, which achieved rapid advance rates despite the challenging ground conditions.

Jan 1, 2003

By R. W. Barbaro, R. V. Ramani

Generally, production planning is concerned with the best use of fixed resources to determine a production schedule for one or more production units supplying one or more markets. Production scheduling determines when each production unit will be used and its production level. However, the production scheduling problems are intimately associated with the location of existing or new production units and processing facilities. Normally, mine location allows only a limited choice; processing plant types and locations are considerably more flexible. This paper presents a generalized multiperiod MIP model as an aid in determining the mine production schedule and the processing plant types and location to satisfy multiple markets. A brief description of MIP and how it has been applied in the mineral and other industries is discussed. A complete description of the model with an application to a coal preparation plant system is presented.

Jan 1, 1987

By J. L. Gent

Compressed air distribution networks are essential for powering equipment in many mines even though some mines are replacing them with electrical power for hydraulic drills. Compressed air can be costly especially if the system is poorly designed and maintained. This paper outlines a technique for proper compressed air system design that will help mine managers reduce compressed air power costs; an important topic in today's highly competitive international minerals market. Compressed air system design is complex. It requires specifying: 1) air quantity and pressure in all branches of a large network, 2) proper location and types of valves and fittings, 3) the network solution that determines compressor requirements, 4) optimal hose and pipe, diameters, 5) receiver and compressor accessories, and 6) required capital and operating costs.

Jan 1, 1989

By T. W. H. Parker, S. B. Sadleir

ABSTRACT A comprehensive program of air flush core and reverse circulation drilling, trial mining and beneficiation test work was carried out in 1980-1982 to re-assess the potential of the Mitchell Plateau bauxite deposit. The results generally confirm previous work by Amax Corporation. The bauxite is a medium available alumina and reactive silica deposit which responds well to wet screen beneficiation. High grade pockets have developed locally, with the potential for refractory grade extraction. A major feasibility study of the Mitchell Plateau bauxite deposit was completed in 1983. Due to the unexpected severity of the downturn in the alumina market, development of the project has been deferred.

Jan 1, 1984

By Ken A. Pfaff, Ray Daigh

This paper will discuss state-of-the-art applications of GPS automation in mobile conveying systems. Robotic mobile conveying systems increase profitability, optimize stacking and reclaiming operations, and control complex interfaces more accurately than other systems. We will also discuss the application process in machine-to-machine coordination, selection of the appropriate GPS system, and Ethernet considerations. As the leading supplier of GPS-controlled mobile conveying systems, we'll draw on our experience at Morenci, Radomiro Tomic, Zaldivar, El Abra (Figure 1), and El Tesoro mines in the US and South America to demonstrate system reliability and the lessons we've learned through analysis of these projects.

Jan 1, 2002

By T. Ko, K. N. Han, C. S. Park, N. S. Kim, C. Yoon, H. Yoon

Quantitative analysis of Platinum Group Metals from ore samples and industrial materials using Inductively Coupled Plasma-Mass Spectrometer (ICP-MS), Inductively Coupled Plasma-Atomic Emission Spectrometer (ICP-AES), Atomic Absorption Spectrometer(AAS), and X-ray Fluorescence (XRF) techniques was conducted and the performance of various techniques was compared. The effects of different matrices in the sample materials were compared and discussed for each analytical technique. The ICP-AES technique exhibited better accuracy than AAS but showed limitations in its application due to strong spectral interference in the presence of common matrix elements such as iron. The ICP-MS showed the lowest detection limit and less spectral interferences than the previous two techniques. The XRF technique was also applied to examine the total amount of PGM from industrial materials. Results from each analytical method on various sources were presented and discussed.

Jan 1, 2003

By N. R. Billette

In 1982 and 1983, a study was undertaken to analyse the applicability of Elbrond?s analytical model to suit the needs of Lake Asbestos of Quebec in their computerized open pit planning and scheduling strategy. The immediate goal was the assessment of the optimal allocation of trucks and the determination of the extra cost of in-pit blending. Data from 45 tonne trucks was used to estimate the mine capacity based on a fixed assignment policy. The tonnage yielded by the analytical model was compared with the results of a simulation program. Another point that the study high- lighted was the definition of efficiency parameters for the haulage system: shovels-trucks-crusher. The efficiency, both of the utilization of financial resources and of the operations, for the overall system reaches optimal values in very precise conditions for the number of pieces of equipment in operation. Such a parameter is proposed as a standard for the definition of an optimal number of trucks and shovels in operation. Deviations from this optimum do occur in a well-planned system for qualitative goals. These can then be quantified in terms of costs to the mining company.

Jan 1, 1986

By R. Bruno

The problem of testing different production strategies has been studied in relation to reserves selection and a computer programme for ore production management has been developed. The case study presented concerns an underground rock salt mine in Sicily with different product lines and variable ore characteristics. A geostatistical block model of the deposit was constructed on the basis of the physical and chemical parameters that ultimately determine the type of end-product in operations according to different selection strategies were simulated using the model and taking account of both technical and 'commercial constraints. The structure of an ore production management programme running on a PC to select both the mining unit and the end-use of the ore is described.

Jan 1, 1989

By L. E. Krys, K. D. Harrison, C. G. Anderson

Since 1984, nitrogen-species catalyzed pressure leaching has been utilized at Sunshine Mining and Refining Company for the recovery of precious metals from a refractory sulfide concentrate. The process operates without the use of cyanide. The plant is now the only industrial-scale commercial application of this technology. Since the inception of the process, changes have been implemented to improve efficiencies and throughputs. Two of these changes, the replacement of nitric acid by sodium nitrite and a concentrate regrind, have recently been implemented. This paper discusses the development and potential mechanisms involved in these recently patented plant-process changes. A companion publication (Anderson et al., 1996) covers the plant integration and potential applicability of the technology.

Jan 1, 1997