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By M. J. Beus

Researchers at the U.S. Bureau of Mines have developed personal-computer-based data acquisition, instrumentation, and mine visualization and modeling techniques to evaluate a mine accessway in a deep hard-rock mine in northern Idaho. These techniques were applied to a mine shaft in a large silver mine that has been in operation for many years. A very deep, rectangular, timber-supported shaft extending to depths exceeding 2.3 km (7,500 ft) had been deforming continuously as a result of nearby mining, resulting in operational problems. Preliminary visual observations and rock and support monitoring confirmed that severe diagonal distortion was occurring. Extensive field measurements and data analysis confirmed initial observations, provided insights into the cause of deformation, and defined a general approach to structural modeling. Computer analysis of the problem was initiated by developing a three-dimensional model of the terrain. This represented a volume of rock approximately 80 km3 (40 x 1010 ft3) and an area on the surface surrounding the mine 9 km2 (3 square miles). Based on this model, a three-dimensional, finite- element analysis was conducted to establish boundary conditions for sequentially more detailed two- and three-dimensional submodels of the shaft area. Results from the computer study are being used to develop new approaches to mine design and to provide design guidelines for deep mine accessways subject to severe rock-mass loading conditions.

Jan 1, 2010

By L. Martins

To increase zinc recovery in the concentrate, this investigation performed mineralogical characterization, dispersion studies, bench and pilot-scale flotation experiments and an industrial flotation trial. The objective was to verify the flotation behavior of the silicate zinc ore (calamine type) in the presence of slimes, with the aid of dispersing agents. Characterization studies identified the major minerals in the flotation feed as hemimorphite (calamine), quartz and dolomite. Dispersion tests showed that enhanced dispersion of the particles in the pulp in the absence of reagents occured at a pH range between 8.5 and 12.0. Bench-scale flotation experiments were planned using the statistical tool of complete factorial design at two levels, replicated once. These experiments showed, and were confirmed at the pilot-plant scale, that higher doses of sodium sulfide and polymeric dispersant combined with sodium silicate favored a higher metallurgical recovery. At 6,800 g/t (218 oz/st) sodium sulfide and 6,992 g/t (224 oz/st) polymeric dispersing agent combined with sodium silicate, a zinc grade of 38.4% in the final concentrate was achieved, at an average metallurgical recovery of 72.4%. The industrial trial confirmed the pilot scale results, leading to zinc recovery of 76.1% and a 37.3% zinc grade in the concentrate. Key words: Froth flotation; Flotation reagents; Flotation depressants; Zinc/ zinc ores

Jan 1, 2010

By C. L. Karr

U.S. Bureau of Mines (USBM) research has shown that fuzzy logic and genetic algorithms (GA's) have great potential for industrial process control. A technique has been developed by the USBM in which GA's are used to substantially reduce the time needed to design fuzzy logic controllers (FLC's).This technique shows promise as an efficient, robust approach to developing control systems. The research described in this report is twofold. First, the basic approach to developing an FLC using GA's is presented. The GA-designed FLC is developed for a specific physical system, a pH titration system. Second, empirical results are presented in which variations in the FLC implementation are compared. Specifically, the effects of altering five aspects of the pH FLC are considered: (1) membership function form, (2) number of fuzzy classes, (3) the center-of-area method, (4) implication operator, and (5) fuzzy rule form. Results indicate that (1) the technique in which GA's are used to design FLC's is effective, and (2) when this technique is used, variations in FLC implementation have little effect on FLC performance in a chosen control problem.

Jan 1, 2010

By T. E. Sedysheva

The study of Co-rich manganese crusts has reached the level which allows to start prospecting works in the observable future, and furthermore, probably, exploitation of ore deposits. In this connection, among other goals, the necessity to analyze a distribution of ore bed parameters in details is quite urgent. Foremost, these are crust thicknesses in connection with landforms and elements of submarine mountains relief. This report is based on representative sampling made in course of research cruises run by SSC Yuzhmorgeologiya over guyots of the Magellan Seamounts. Crustal covers could overlie seafloor surfaces which are confined to a various landforms and elements of relief under the condition, that they are free of sediments. These are planed parts of a summit surfaces, edges, spurs, rectilinear parts of slopes, intermountain saddles and volcanic edifices. It is known, that crustal thicknesses are different at a various forms of relief [1]. We processed statistically the data around crustal thicknesses, which were sampled by dredging and submersible drilling (Tables 1, 2).

Jan 1, 2010

By Rodrigo Toro, Ivan Yutronic N

"The Copper Concentrator Plant of Compañía Minera Doña Inés de Collahuasi (CMDIC) is composed of three grinding lines, the third one being the largest. Due to the capacity feature of the third line, specially its SAG mill, it is a priority that the advanced process control team of the Company deploys a supervisory control strategy that allows this unit to operate in an optimal way, in order to achieve the maximum productivity at minimum cost. It is in this kind of tasks where advanced control applications play a key role in obtaining the best economic profit of the process.The advanced process control team, formed by people from Informatics, Automation and Operations of CMDIC have assumed the challenge of generating the transition from a manual SAG Mill 1011 operation (40 x 22 feet, the largest copper SAG mill of the world), to a fully automatic SAG Mill using a multivariable control strategy instead of a rule based on expert control system (widely used in industrial mining process control applications).Therefore, CMDIC decided to work together with Honeywell APC Team implementing an advanced automatic control strategy for the SAG Mill 1011, using for this purpose a technology called Model Based Predictive Control (MPC), based on a variety of control methods that uses dynamical models of the process, obtained from input/output data, in order to print the process knowledge into a group of mathematical relationships that links the constraints (controlled variables) with available commands (manipulated variables) and measured disturbances.The main objective of the advanced control strategy is to ensure process government, tending to throughput stability and optimization, by the execution of coordinated control actions, proactively avoiding measured disturbances effects and the SAG mill overloading.The most important benefits of using a multivariable control strategy are: the automated operation of SAG mill 1011 (that was manually operated before the implementation of this application), a safer, more coordinated and more stable process operation, achieving through this an increase of throughput and a decrease of specific energy consumption, controlling the amount of oversize material production, power consumption, mill loading, noise and torque. In addition to the operational results, this challenge has consolidated a control team, with the participation of engineers and operators, diminishing the typical implementation time and achieving a greater use of the application in a short time."

Jan 1, 2010

By M. Rodgers

Dow Water & Process Solutions (DW&PS) was approached by ASARCO Inc. to attempt to recover cobalt and copper from their copper solvent extraction (SX) raffinate. Cobalt is added to many copper electrowinning tankhouses to help to prevent lead electrode corrosion. With cobalt?s high price this can be a large expense. ASARCO has ore that contains a small amount of naturally occurring cobalt. Currently they have no way of capturing this high value metal from their leach or raffinate streams. DW&PS has some chelating resin technologies that should be able to help solve this problem.

Jan 1, 2010

By A. J. Dudzik

In 2006 Arch Materials initiated the development of an underground limestone mining complex. The decision to proceed with the project was the end result of several years of market research and geological reconnaissance. The scope of the project included the construction of two declines to the mining horizons located approximately 900 feet below the surface, the means and methods of this phase will be the primary focus of this discussion. The design, fabrication and erection of a state of the art crushing and screening processing plant which when completed will have the primary crushing located on the mine level allowing uniformly sized material to be brought to the surface by means of a highly efficient conveyor system and a surface portion of the plant where material would be additionally processed, screened and stockpiled into specific product types. Also included in the scope of the project is the construction of offices, warehouse and shop facilities necessary to support the operations, commercial sales and distribution of the finished products.

Jan 1, 2010

By Laxman S. Sundae

Laboratory tests were conducted at the U.S. Bureau of Mines to determine the effects of roof-bolt drilling parameters on penetration rate in sandstone using tungsten carbide alloy (WC-Co) and polycrystalline diamond compact (PDC) drill bits. During the tests, water pressure of 552 kPa was found to be adequate for removing the cuttings from the tops of drill holes. Test results show that for both types of bits, penetration rate increased when thrust was raised from 227 to 1,588 kg. When water pressure rose from 554± 120 to 1,344±350 kPa, the effect on penetration rate was not significantly different. Conventional WC-Co bits became dull when one or two holes were drilled, after which the penetration rate dropped dramatically. Microscopic examination shows that the cutting edges of PDC bits also become somewhat dull, but at a much lesser rate than WC-Co tips. Microscopic examination also reveals that the wear mechanism of WC-Co and PDC bits is quite different, which may explain the longer life of the PDC bits.

Jan 1, 2010

By W. H. Strickland

Ultrasonic ranging sensors are inexpensive, have no moving parts, have no lenses to clean, are normally small and unobtrusive, and can measure distances through moderate amounts of dust, smoke, and humidity, so they are well suited to underground mines. In the work reported here, conducted by the U.S. Bureau of Mines, researchers tested ultrasonic ranging sensors for their ability to define rib line features for computer-aided navigation of underground mine mobile equipment. The investigation began with laboratory tests of field of view, angle of incidence, intersensor variation, and ranging accuracy of the individual rangers in a ring array produced by Denning Robotics of Wilmington, MA, The results showed that the sensors have good accuracy and low variability. Additional experiments at AMAX'S Henderson Mine showed the sensors could accurately and reliably measure the distance to mine features, including convex and concave corners and rib intersections. The results showed that when used properly, the ranger data are accurate enough for reliable mine vehicle navigation. When used incorrectly, ultrasonic rangers do not provide the anticipated data. Therefore, this report explains the principles of ultrasonic range measurement, describes the ranger's strengths and weaknesses, and explains proper ranger use and data analysis.

Jan 1, 2010

By R. L. Levens

The Underground Injection Control program was promulgated in 1981 by the U.S. Environmental Protection Agency under the provisions of the Safe Drinking Water Act. Placement of mine waste backfill underground is considered underground injection under the provisions of this program. A major issue is whether mine waste that is regulated as a contaminant source on the surface should be disposed of underground. The U.S. Bureau of Mines conducted research to investigate the impacts of mine waste sandfill on the quality of ground water. Analyses of water samples collected before and after contact with sandfill in a 10-year-old stope, as well as samples of the sandfill itself, were used to ascertain the influence of the sandfill after mine closure and subsequent flooding. Computer models supported the hypothesis that oxidation of pyrite by oxygen, accompanied by dissolution of carbonates, was the predominant reaction controlling the quality of the water being discharged from the stope. Concentrations of metals released as a result of acid production remained near or below detection limits. Metals release after mine flooding is expected to remain low as a result of the buffering by the sandfill and the reduced rate of oxidation.

Jan 1, 2010

By W. P. Stroud

In this U.S. Bureau of Mines report, the conditions required for the direct reconstruction of a tomogram from observed line integrals are examined. Because of the limited access to the working faces in coal mines, the special case of access to only two opposite faces is emphasized. Classical matrix methods were used for small dimensional (2 by 2, 3 by 3, and 4 by 4) applications to determine the limitations and the requirements for a solution. The results for large (n by n) grids were then inferred and generalized from those of the smaller grids and matrices. Limited access tomography is found to be appropriate for in-seam hazard detection from seismic and microwave data, but it is shown that additional data must be added to obtain a direct solution.

Jan 1, 2010

By Tony Lipiec, Greg Gosson

"When it comes to new mines being developed, there is a general industry consensus that most low-hanging fruit has been picked. Many projects currently in the mine development pipeline have been around for decades, but were held back because of technical challenges. Future development of these deposits will likely require access to the public capital markets, and in Canada that means providing scientific and technical disclosure on these deposits in compliance with NI 43-101. As many of these “challenged” projects have metallurgical issues, the companies that own the projects need to ensure their metallurgical Qualified Persons provide transparent disclosure regarding proposed solutions to those issues.This paper provides an overview of the disclosure requirements under NI 43-101 that are pertinent to metallurgists, and other Qualified Persons who prepare technical disclosure regarding the metallurgical characteristics of a mineral project. It lists the triggers for a technical report under NI 43-101 and Canadian stock exchange policies, and identifies the sections of the report that should involve input from a metallurgist or process engineer. It briefly outlines new civil liabilities under Canadian securities laws that increase the possible consequences for not complying with the technical disclosure standards.These materials are provided for general information purposes only and do not constitute legal advice. Readers are advised to seek specific legal advice from their own legal counsel in relation to any decision or course of action contemplated."

Jan 1, 2010

By T. Eggenberg

Mechanization and automation of logistic equipment has become one of the main key factors in raising productivity and competitiveness especially for complex and larger mining or tunneling projects. The Lake Mead Intake Tunnel #3 shaft mucking installation is a good example to demonstrate the potential that is found in an overall optimized logistic. It starts with the planning and results in using customized installations which fulfill the specifically defined requirements for the project. Rowa developed a solution and supplied a shaft mucking system using a discontinuous double drum hoisting concept with shaft buckets, loading, and unloading devices. With this fully automated system a continuous muck flow of 437t/h can be achieved.

Jan 1, 2010

By Craig C. Hustwit

A pilot-scale treatment study was conducted on a copper-zinc bearing metal mine drainage using a pipeline treatment system called the In-Line System (ILS). The objective of this U.S. Bureau of Mines study was to determine whether the ILS could be extended from the treatment of coal mine drainages to the treatment of metal mine drainages. Hydrated lime (Ca(OH)2), quick lime (CaO), and caustic soda (NaOH) were used to neutralize the drainage. A novel reagent slurry of Ca(OH)2 and type C fly ash was also evaluated. Except for Ca(OH)2-fly ash slurry, treatment performance was evaluated for all reagents at pH values of 7,8,9, and 10. The Ca(OH)2-fly ash slurry was evaluated at a pH of 10. All reagents tested neutralized the metal mine drainage and substantially reduced the dissolved metal concentrations. It was concluded that the ILS could be useful in the treatment of metal mine drainages.

Jan 1, 2010

By William P. Stroud

Chemical alteration of the compressive strength of sandstone has been investigated by the U.S. Bureau of Mines (USBM). Successful development of this technology would offer an attractive alternative to the methods now used for stress control in mines. Sandstone cores were stressed to failure under uniaxial compression at two different strain rates. Specimens saturated with either distilled or tap water showed an average 14% reduction in stress at failure compared with those dried in vacuum. Samples saturated with dilute solutions of aluminum chloride, hydrochloric acid, and polyethylene oxide showed no statistically significant difference in failure stress compared with those saturated with water. By contrast, compressive strength of the cores was increased some 7% by saturation with the nonpolar solvent carbon tetrachloride. No correlation was found between zeta potential and compressive strength.

Jan 1, 2010

By Charles D. Litton

This U.S. Bureau of Mines report details the results of a series of large-scale experiments where small coal fires were used to ignite the conveyor belt at air velocities ranging from 0.76 to 6.1 m/s. In the tests, electrical strip heaters imbedded within a pile of coal were used to heat the coal to a point of flaming ignition. The flaming coal subsequently ignited the conveyor belt located approximately 5 to 10 cm above the coal pile. During the tests, temperature, CO, and smoke levels were continuously measured in order to determine both alarm time and level as the fire intensity progressed through the stages of smoldering coal, flaming coal, and flaming coal plus flaming belt. Analysis of the data leads to certain conditions of air velocity and sensor alarm levels that are required for early detection of conveyor belt entry fires. Two nomographs are presented, which define sensor alarm levels and sensor spacings as a function of belt entry cross-sectional area and belt entry air velocity.

Jan 1, 2010

By P. A. Roberts

A proposal for a modified in situ leaching method for extracting gold from oxidized gold ores using a non-cyanide lixiviant is described. A non-cyanide lixiviant is suggested because of the obvious concerns posed by injecting cyanide-bearing solutions into the subsurface. Oxidized gold ores were chosen as a focus because earlier research on the use of sodium thiosulfate as a lixiviant under anaerobic conditions indicated that the presence of pyrite led to rapid thiosulfate breakdown. A reconnaissance research program involving ore characterization and hydrometallurgical test work on samples from four Australian ore deposits and preliminary reactive transport modeling studies was carried out. This work showed that lixiviant-oxidant combinations of sodium thiosulfate and ferric EDTA and iodide and iodine are both capable of extracting high percentages of accessible gold from the selected samples in bottle roll tests under anaerobic conditions. The ore characterization and reactive transport studies suggested that both physical and chemical methods of permeability enhancement may be required to lift bulk permeability and the availability of gold for dissolution to sufficiently high levels to obtain adequate gold recoveries. Assuming that such methods prove to be both necessary and economically viable, the mining method would no longer be regarded as simple in situ leaching. Therefore, the term ?in-place leaching? has been adopted for the proposed gold extraction system.

Jan 1, 2010

By W. W. Hartley

Following a Major underground coal mine incident there followed a review of the role of mines rescue ? the Queensland Mines Rescue Brigade. It wasn?t until 2002 that the real change started to happen. The issue of geographical distance was addressed by mines rescue sub stations being located on the mines sites with parent rescue stations in a central location. The funding was by means of a levy on the mining industry with legislative standards and performance included. The previous Rescue Brigades were not well organised (central districts) and the application of recognised quality management practices within local management was lacking. The structure was based on other nations models and miners managing miners was an issue for the organisation. The reform was some what painful and the QMRS organisation will still evolve with continuous improvement. Queensland has the National Champion mines rescue team for the eighth year. QMRS is participating at the level in the industry of influencing emergency systems and training senior mine management in ?Emergency Mine Management? coaching the industry in emergency response systems. We have come a long way. We have had some success and there is always the challenge of setting the standards, those we should aspire to and the courage to influence the industry to higher goals of a safer future.

Jan 1, 2010

The extraction and recovery of gold from copper electrorefining slimes by leaching and solvent extraction using dibutyl carbitol (DBC) has been practiced for several decades. Yet, the deportment of some common elements in this process has not been reported. The focus of this paper is to report the behavior of copper, bismuth, silver and selenium during the processing of industrial solutions by batch and continuous extraction on the laboratory scale. It was found that DBC, while an excellent extractor of gold from a highly oxidative chloride leach solution, also loads significant quantities of Cu, Bi, and Se. Silver was not present in significant quantities in the leach solution nor did it load appreciably. The deportment of gold and impurities are reported for batch and continuous operations of a two-stage extraction process using distribution ratios and separation factors.

Jan 1, 2010

By S. Angioletti

This paper addresses strategic investment decisions when they are nested in a project development format where each project is implemented in phases and each phase is approved to move on to the next phase only if certain technical and economic requirements are met. This configuration is sometimes referred to as a ?Project Portfolio?. Mining companies maintain project portfolios in their exploration investment plan. This study proposes a procedure to best manage an exploration project portfolio including technical and economic uncertainties. The procedure may support decision makers in a simple and intuitive way, while maintaining the rigor and precision required by the rather large amount of financial resources typically called for by mining projects. The procedure was tested in a real case study of a gold mining company and its exploration projects portfolio. The procedure uses the following approaches: i) investment valuation methods under technical and market uncertainties based on Option Pricing Model, Real Option Theory and Option Space; ii) portfolio management and Stage Gate®1 method; iii) Monte Carlo simulation.

Jan 1, 2010