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By Kent S. Roessler

The Bureau of Mines is currently investigating the geophysical application of Tomography to monitor leachate during in-situ mining. Determining the location of the leachate is important for both economic and environmental reasons. By analyzing a sequence of tomographic images, we can determine where highly permeable/fractured regions are located and hence, major flow paths. Since BOMTOM (Bureau Of Mines TOMography - Tomographic Reconstruction Program), and BOMCRATR (Bureau Of Mines Curved RAy Tomography - Tomographic Reconstruction Program) are sensitive to user-selected ray path arrival times, we are also investigating the use of neural networks to automate the process of recognizing this feature. This paper presents a technique for detecting fracture zones and their orientations in a region between two boreholes, by using a motion analysis study of a sequence of tomographic images. It also addresses the need for an automated/unbiased method to pick crosshole seismic arrival times using a trained neural network. In exploration geophysics, the picking of first break arrivals represents a pattern recognition task. The neural net paradigm has proved to be a good method of solving this type of task. To pick the first arrival peak of a trace, the network is trained with a set of known (user selected) first arrival peaks by creating a binary image of a set of traces. Once trained, the neural net correctly picked first arrivals of the remaining traces in the set.

Jan 1, 1992

By J. M. Scharer, Bruce E. Halbert, Pettit. Carol M., Lysane Bolduc

The ratio of neutralization potential (NP) to acid production (AP) ratio is often employed for predicting acidic discharges from waste rock dumps. The available NP was evaluated in laboratory studies of limestone dissolution in simulated acidic mine water. The available neutralization potential strongly depended on the particle size. Using limestone particles of 114" (6.4 mm) or greater, less than 20% of the total neutralization potential was exhausted at the onset of acid conditions. Apparently, the dissolution of limestone became mass transfer limited. Under mass transfer limitations, the rate of pyrite oxidation may exceed the rate of neutralization by buffering minerals. The implications concerning the controls on limestone dissolution were examined using a geochemical predictive model for sulphide mineral oxidation in waste rock. The results have shown that in case of heterogeneous waste rock piles the NP/AP ratio is a reliable indicator for short-tam predictions only. Kinetic data on the depletion rate of the neutralizing minerals and geochemical modelling suggest that waste rock environments with NP/AP ratios as high as 5.0 may turn acidic in the long term.

Jan 1, 2000

By S. A. Matthews, M. L. Nave

AC variable frequency motor drives are emerging technology for belt conveyors. The success of the application in mining depends on adequate and timely consideration of drive, motor, and conveyor features. The purpose of this paper is to familiarize and inform possible mining users of AC variable frequency drive attributes.

Jan 1, 1998

By L. Yuan, J. H. Rowland, R. A. Thomas

"Hydrogen (H2) gas released during battery charging can result in cross-interference for carbon monoxide (CO) sensors used for early fire detection and compromise the integrity of the mine atmospheric monitoring system (AMS). In this study, a series of laboratory-scale and full-scale experiments were conducted to evaluate the responses of different CO sensors to H2 gas. In the laboratory-scale experiments, constant H2 concentrations in the airflow, from 100 to 500 ppm, pass through sensors. While in the full-scale experiments, increasing H2 concentrations generated as a byproduct from charging the batteries at the battery charging station rise to the sensors under different ventilation scenarios. The H2 concentrations at the CO sensor location were measured using H2 sensors and were correlated with the CO sensor response. The effects of ventilation and sensor location on the CO sensors responses were also analyzed. The results of this study can help mining companies to select appropriate CO sensors and improve the deployment of these sensors to ensure the safeguard of underground miners. INTRODUCTION As many types of battery-powered mining equipment such as scoops and shield haulers are used in underground mining operations, charging stations are required to charge the equipment batteries. These batteries are of lead acid chemistry. A safety issue exists with the battery charging stations as all lead acid batteries produce flammable H2 gas during the normal charging process. Overcharging or excessive heat can quickly cause batteries to produce even more H2. If H2 is not appropriately diluted or dispersed, it builds up, and the risk of fire and explosion increases. Mine Safety and Health Administration (MSHA) regulation (30 CFR Part 75.340) requires that battery charging stations should be housed in noncombustible structures or be equipped with a fire suppression system. When a fire suppression system is used, the battery charging stations must be ventilated with intake air that is directed into a return air course or ventilated with intake air that is monitored for CO or smoke using an AMS. The monitoring of intake air ventilating battery charging stations should be done with sensors that are not affected by H2."

Jan 1, 2018

By Alena Conrads, Markus König, Markus Scheffer, Markus Thewes, Hannah Mattern

"INTRODUCTION In recent years, the development of tunnel boring machines has revolutionized the tunneling industry. The general structure of a tunnel boring machine (TBM) can be described as a multi-component system. To achieve high performance rates, machine elements have to perform reliably. Performance losses and interruptions of the construction process should be prevented or at least, reduced to a minimum. In order to achieve high advancing rates, cutting tools must be in good condition at any time. Furthermore, failure of individual tools might result in increased and faster wear of remaining structural components. For this reason, maintaining and replacing cutting tools is crucial to prevent project delays due to insufficient boring performance. Precise prognoses concerning the prevailing geology are infeasible and thus, efficient scheduling of maintenance actions is challenging. The intention of this work is to analyze different approaches of TBM maintenance in soft ground. Different strategies are analyzed by the use of a simulation approach. Cutting tool condition is regarded as performance limiting factor. The maximum operation time of the cutting tools is determined using the “Soil Abrasivity Index”. A case study serves to show the effects of different maintenance strategies on total project duration. SCHEDULING OF MAINTENANCE ACTIONS Scheduling maintenance actions of single and multi-component systems concerns numerous fields of industrial production. Concentrating on mechanized tunneling in soft ground, cutting tool maintenance represents the most common reason for intermission of advance (Köppl 2014). In literature, time-based and condition-based maintaining techniques are widely discussed. The following section outlines the principles of time- and condition-based policies. Furthermore, examples for their applications in recent research are given. Time-Based Maintenance In general, the time-based maintenance approach assumes that the failure behavior of the system components is predictable. Maintenance actions are scheduled according to predefined intervals (e.g., hours, days, weeks). A detailed analysis of preventive repair times or interval forms the basis for maintenance decisions. For this approach, an adequate quantity and quality of data is fundamental. Numerous studies deal with the analysis of time-based maintenance for production equipment. In fields of mechanized tunneling, unplanned machine downtimes restrict the applicability of time-based maintenance approaches. Thus, this paper mainly focuses on condition-based maintenance."

Jan 1, 2016

By Robin J. Batterham, Dave J. Robinson

The most significant trend in flotation has been the ever-increasing scale of operations. There is, however, doubt that this ongoing trend is enough to maintain the economics against trends such as falling grades, increasing mining costs, pressure on water supply and demand, rising energy demands needed for mineral processing, and a focus on whole of life value and mine legacy issues. We comment on the ramifications of broader uptake of more sustainable mining for mineral processing methods and address the specific question of whether recent progress in in-place recovery will lead to a timely breakthrough. The answer proposed is that this is possible in the next 10 to 20 years, but in the meantime the focus is just as likely to be on removal of waste (beneficiation) much earlier in circuits. Either way, mineral processing and flotation as we know it will change significantly. 

By K. J. Stanaway

Environmental pressures on waste disposal are forcing pigment producers to use feedstocks with higher Ti02 content and lower levels of trace elements. Despite this, 50% of the world's Ti02 comes from ilmenite concentrates with only 37% to 54% Ti02. An industry growth rate of 25% in the next 10 years, combined with trends to diminishing resources and lower mining grades for rutile (95% P02) and leucoxenized ilmenite (55% to 90% P02), means that unless new discoveries are made soon, the industry will become even more reliant on ilmenite.

Jan 1, 1995

By R. W. Lai

Cyclic voltammetry (CV), flotation response, evolved-gas analysis (EGA), and X-ray photoelectron spectroscopy (XPS) were employed to evaluate the major differences in the surface property and surface reactivity of coal pyrite and mineral pyrite.

Jan 1, 1989

By J. P. McKinney

Benchtop experiments were performed, in which an electric field was used to enhance separation of water from phosphatic clay suspensions from a central Florida mine. A constitutive relationship was established that relates the increase in solids content to operating time and the applied electric field. An upper limit to the degree of separation was found to be a function of electric field, and the time required to achieve this limiting value was also a function of electric field. The energy requirement for removal of water ranged from 1.25 to 175 Wh/kg water removed as a function of the electric field. A mathematical model was developed that provided good agreement to the experimental values and served to validate the constitutive relationship.

Jan 1, 2011

By T. Y. Yan

An effective elution technique has been developed for recovering uranium from ion exchange resins loaded in the carbonate leaching process. The procedure employs direct elution with acid. In comparison with conventional base elution, the procedure yields eluate of higher uranium concentration, results in a more complete elution, keeps the performance of the ion exchange resin at the fresh stage, reduces acid consumption, eliminates carbonate consumption, and reduces waste for disposal. The technique has been successfully demonstrated in the field and patented. It lends itself to commercialization.

Jan 1, 1987

By H. Huang, J. C. Wu, C. H. Xie, Y. Q. Xue, Z. H. Zhang

Two- and three-dimensional groundwater flow models for dewatering in an opencast mine are presented. The models focus on solving special problems using numerical simulations of the opencast mine. These special problems include the drying up of the aquifer, the movement of the model boundary and the prediction of the residual head. These models are used to describe the decline of groumdwater levels in the Yuanbaoshan Opencast Coal Mine and its neighboring area during the drainage period. The simulated values agree very well with the field data. There have been several successful examples of numerical simulation for predicting the mine dewatering rate in an opencast mine. However, The hydrogeological conditions for the Yuanbaoshan Opencast Coal Mine are rather complex, and the total average flow rate is very high at 4.676 x 105 m3/d (1.65 x 107 cu ft/day). In this paper, a two-dimensional groundwater flow model in a large area is developed to solve the problems mentioned above by simulating regional drawdowns of the groundwater level during the drainage period, and a three-dimensional flow model is developed to simulate the residual head near the open-pit bench.

Jan 1, 1998

By J. G. Groppo, D. J. Sung, B. K. Parekh

Hyperbaric filtration for the dewatering of fine coal cleaned by froth flotation was evaluated on a laboratory scale. A laboratory pressure filtration procedure designed to obtain a uniform cake structure from dilute slurries containing a significant amount of coarse material is described. Baseline tests were conducted to determine the optimum operating conditions for the eventual application of the process to a continuous pilot-scale hyperbaric filter. Investigated were filter operating parameters such as driving force, time, cake thickness, percent solids, viscosity and pH.

Jan 1, 1996

The mining industry has indeed gone global. International minerals producers are spending big money to move into countries that were off limits a few years ago. Due mostly to political reasons, these countries' huge mineral deposits - worth billions of dollars - were locked up and mining companies could only sit on the side and wonder "what if." Now much of the world is going the free market route. Once closed countries and developing nations are rewriting their mining and tax laws hoping to attract foreign investment to develop their natural resources. And big businesses - mining companies included - are lining up to get their share. But with new opportunities come new risks. While emerging nations are slowly accepting the free market concept and the privatization that goes along with it, many remain plagued with political instability and violence. Even developed nations carry their unique risks. Some of these include inadequate or contradictory legal and regulatory infrastructures, political patronage and outright corruption. So companies hoping to expand into new regions of the world must do more than examine the market. They must study the political stability and structure of a country, as well as its tax and environmental laws. And they must guarantee the safety of their employees. Control Risks Group is an international management consulting company that assists companies preparing to move into a new country. It employs about 225 people in 14 offices throughout the world. Control Risks personnel include lawyers, bankers and former law enforcement officers and intelligence people. The company held a one-day seminar in Washington, DC to update some of its clients on the state of affairs in various regions of the world. The seminar also covered extortion, corruption and product diversion. About 175 people attended the seminar. Speakers included Control Risks' operators, analysts and investigators. Here is a summary of what some of those people had to say.

Jan 1, 1998

By A. I. Kalugin, A. A. Abramov, D. E. Kozlov

As a result of thermodynamic analysis of a mineral-sodium, oleate-water system, flotation and adsorption tests at various pH values, and sodium oleate concentrations, it has been established that due to regularities of phosphate-containing minerals (fluorapatite, hydroxyapatite, carbonatapatite) flotation cannot be explained by the formation of alkali-earth metal oleates on their surface. This paper presents a novel theory that connects optimal conditions for mineral flotation with zero charge of its surface, which can explain the regularity of minerals flotation observed. The quantitative physicochemical flotation models developed based on the theory are suitable for improving industrial processes, conditioning of recycling waters, and application in automatic control systems at the plants. Key words: apatite, oleate, flotation, modeling, control, and regulation.

Jan 1, 1999

By Norbert Patzelt

The high-pressure grinding roll was introduced about 10 years ago and has established itself in many applications. Most of these machines are used in grinding circuits in the cement industry. A few operate in conventional mineral-processing plants. Polysius has sold more than 350 Polycoms worldwide. An exception is diamond-ore processing in South Africa and Australia. This type of grinding system increases diamond liberation and reduces the capital costs for the downstream processing plant. There are several reasons why high-pressure grinding rolls have not been used more extensively in the mining industry: - The mining industry adheres to conventional grinding technology and regional preference for certain comminution circuits. - Design, scale-up and flowsheet assessment procedures are viewed as being immature and reduce confidence in the potential application of the technology. - Downstream process benefits are unproven on a plant scale.

Jan 1, 1995

By E. M. Van Eeckhout

The National Uranium Resource Evaluation Program (NURE) has produced a mass of geochemical data in the form of data files on tapes. This paper presents a methodology for utilizing those tapes in a simple, practical manner. An example is given of an analysis of the Butte quadrangle, Montana, tape obtained from the Los Alamos National Laboratory (LANL). The example details the sequence of splitting the data file, plotting histograms, cumulative frequency curves, concentration plots, and methods for evaluation. All programs are written in FORTRAN. The case study was performed using a mini- computer (DEC PDP 11/70) and standard plotting subroutines.

Jan 1, 1982

By P. Arell, D. Folkes

This paper presents the basics of EPA’s Hazard Ranking System (HRS), which is used to evaluate sites for possible inclusion on the Superfund National Priorities List (NPL). The paper describes the surface water, ground water, air, and soil exposure pathways and how they are applied to mining sites. Key factors contributing to the site score include the likelihood of a release, waste characteristics, and the targets for each pathway. Waste volumes, definitions of landfills versus surface impoundments, and background concentrations are of particular importance to mining and smelting sites. Because of the presence of metals, large waste volumes, and observable releases, mining and smelting sites often receive high enough scores to be proposed for the NPL based on a single path-way. Neverthess, owners and operators can take steps to reduce the risk of being scored, and to reduce the potential for high scores.

Jan 1, 2004

By Gurses Oner

In situ leaching is a relatively old mineral extraction method; however, historically only a small portion of copper has been produced from small scale operations. Recently, in situ leaching technology because of its intrinsic advantages over conventional mining and milling is being considered as a viable option for recovering copper from both low grade oxide and sulfide deposits. This paper presents the application of computers to investigate in situ technology using large whole core leaching experiments. Computers were applied to three different areas: (1) experimental control and data acquisition, (2) non-destructive evaluation of samples using x-ray computed tomography and image processing and (3) mathematical modelling and data analysis.

Jan 1, 1992

By F. F. Peng, D. C. Yang, G. Yanief, E. H. Cho

This study deals with carrier flotation of cerium dioxide, a surrogate of plutonium oxide, which is the major contaminant at the Nevada Test Site (NTS). The objective of this study was to determine the feasibility of using carrier flotation for remediation of the site. In this study, a - 200-mesh fraction of pure cerium dioxide was used. Oleic acid was used as the collector, while calcium carbonate was used as the carrier. Mechanical-cell tests were conducted to float the surrogate from a mixture containing uncontaminated NTS soil, both in the absence and presence of the carrier. It was found that the addition of the carrier drastically enhanced the flotation recovery of cerium dioxide. The flotation recovery of the surrogate increased from 34% to 65% by adding only 0.5% calcium carbonate (-150 mesh). The recovery further increased to 95% by adding 10% calcium carbonate. The flotation method utilizing a carrier of calcium carbonate seems to have a high potential for the remediation of the soil contaminated with radionuclides at the NTS.

Jan 1, 1998

By Gemei Yang, Pierre Mousset-Jones, Felipe Calizaya, Malcolm J. McPherson

Laboratory tests on controlled airflow recirculation have shown the development of transient states in response to changes in system prevailing conditions such as those generated by a sudden start-up and stoppage of fans. Researchers in many European countries have developed various models to explain these phenomena. However, these models failed to consider some important factors such as diffusion and dispersion of gas in turbulent flows. For both in-line and cross-cut recirculation, tests have shown that after the start- up of a booster fan, the gas concentration in the system fluctuates, reaching high levels at the initial states and slowly dying out with time. These fluctuations cannot be represented adequately by simple step-wise functions but rather by smooth, albeit complex equations. In this paper, the phenomena are explained by the convection-dispersion theory, and represented by a mathematical model. Based on a few simplifications and applying Fourier's Transform Method to the differential equations of the flow recirculation model, an integral form of gas concentration function was derived. The Simpson Integration Method was used to compute numerical results for two laboratory tests. The paper also discusses the range of the dispersion coefficient to improve the accuracy of the model.

Jan 1, 1989