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By O. A. Bascur

An expert process operation advisor system can increase plant efficiency, even in a complex, natural environment where not all elements of the production process can be measured directly. This system, develaped and tested in a Frasch process sulphur mine, monitors key process variables with extended qualitative pattern processing and provides on-line advise to the operators of sulphur production wells. An expert system framework captured common sense rules generated from years of experience obtained in the operation of a sulphur well monitoring system. The existent operating procedures were enhanced by process analysis using a qualitative modeling approach which provided extended rules for on-line classification of a well operational status and an expert alarm system. The methodology for development and implementation of the process advisor is presented in this report. Qualitative process modeling, statistical process control and heuristics were incorpomted into the process advisor resulting in a more efficient use of heat, an extended well operational life and the resulting cost savings. The computer process advisor also allowed the operator to concentrate his attention on the weak wells or wells in trouble. A process management system improved plant operation by automatically storing well data into a commercial database for operator validation. The enhanced relational data base system provided valuable and timely information for planning and decision making. The synergistic combination of on-line process analysis tools, expert control systems and database technology is shown to facilitate the flow of materials, energy and infomation in a modern plant.

Jan 1, 1990

By Jan E. Stache

Commercial software programs are being utilized to create and maintain a mine subsidence database in conjunction with the U.S. Bureau of mines research on mine subsidence in Illinois. A three-year survey net of monitored structures in an Illinois subdivision was entered as textual information (attributes), on an existing AutoCAD drawing. These attributes can be optionally displayed on the corresponding drawing or extracted as a text file for import to a database program. The database program, dBASEIV, allows combinations of multiple database files for extensive querying capabilities. Subsurface database files can be merged with surface database files to enhance the effectiveness of surface response analyses in mine subsidence research. The geographic information system (GIS), pcARC/INFO, was chosen to integrate existing AutoCAD drawings and dBASEIV database files into a relational database with a graphical representation. The relational database allows users to update either the graphical representation or the database, with the changes being reflected automatically in its alternate format. The increased capacity, through use of a GIS, to query combinations of database files and have the results reflected graphically has significant potential for expediting mine subsidence research.

Jan 1, 1986

By Joseph M. Tarantino, Eric F. Perry, Keith B. C. Brady, Michael W. Smith

The Pennsylvania Department of Environmental Protection in 1998 reviewed its permitting process to determine how effective its program has been in preventing pollution and to identify here it could be improved. Of the 1,699 bituminous mine permits issued from 1987 to 1 996, 50 were identified to have current or past postmining discharges with water quality problems. The remaining 1,649 sites had no known current or past postmining discharges problems. The 50 sites were selected for further review. On closer examination, 33 of these permits no longer had water quality problems or the problem had not actually resulted from the permitted mining activity. Only 17 permits, or one percent of the total permits issued, were found to have caused long-term postmining discharges serious enough to require treatment and prevent bond release. Analysis of these 17 sites using current knowledge of mine drainage prediction, revealed that the most common cause of error was inadequate information in the permit application. Errors in interpretation of the application data and in implementing the permit were less common. A very small percentage of all permits issued resulted in postmining discharges for no clearly identifiable reason. Trends over the 10-year study period indicated a decreasing incidence of permits resulting in postmining discharges. Further, with the exception of the first few years of data, most of the postmining discharges were of mildly acidic or alkaline quality and amenable to passive treatment.

Jan 1, 2000

By A. F. Alsobrook

Specialty silica materials, as defined in this chapter, are rocks that consist predominantly of silica (SiO2) and are produced as chunks, round pebbles, and sawed or trimmed blocks and other shapes for nonconstruction applications. The rock types include quartzite, sandstone, novaculite, flint, chert, and vein quartz. Other terms used commercially include jasper, silex, lascas, and rock crystal. In its publication, Minerals Yearbook, the US Bureau of Mines (USBM) reports the production and consumption of some specialty silica materials under several headings. Quartzite, sandstone, and novaculite used in abrasive applications are addressed by the USBM under Abrasive Materials. Lascas, a type of vein quartz used in growing synthetic quartz crystals and in fusing applications, is discussed under Quartz Crystal. Silica gravel used in manufacturing silicon metal and ferrosilicon, as metallurgical fluxstone, and as a filtration medium is covered under Industrial Sand and Gravel. Information on

Jan 1, 1994

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 Colin J. Booth

Hydrogeological impacts of active longwall mining were studied at two sites in Illinois. At the site with the more transmissive sandstone aquifer, aquifer permeabilities increased an order of magnitude due to subsidence. Piezometric levels declined with subsidence due to increased porosity, and ahead of mining due to a transmitted drawdown. Levels recovered rapidly at first and fully over two years. At the site with the less transmissive aquifer, impacts were similar except that recovery has been limited. Local aquifer enhancement through increased yield can occur, but only where the aquifer is transmissive enough for recovery.

Jan 1, 1986

By Hans von Michaelis

Gold metallurgy has advanced remarkably over the last decade. Even more significant progress will be made over the next five years, particularly in the application of advanced comminution techniques and control, preconcentration (flotation, ore sorting and coal gold agglomeration), enhancement of cyanide leaching technology, non- cyanide leaching, treatment of refractory ores and concentrates, and improved recovery systems. Carbon adsorption processes have become standard practice for ores with relatively high gold/silver ratios, but ion exchange potentially offers distinct advantages and has recently been demonstrated to perform better in at least one application. Even in the established zinc precipitation and CIP processes several important practical improvements are emerging as experience is gained at the ever increasing number of operating plants. Improved process control and reduction of reagent consumption costs are two important goals of industry at this time.

Jan 1, 1989

By R. H. T. Garnett

Recovery performance may be measured in absolute terms or in relative ones that relate the actual mining outcome to what was expected. Consideration is possible in terms of the control exercised by the operator. The eventual mineral output is the only figure known with complete certainty. The paradox is that, while performance is judged against the sampling, the reverse also applies. The R/Efactor and its four component factors are the best overall measures of performance. The choice of equipment for sampling and mining is very important. The sampling process may introduce errors and the sample density may lead to poor mining block selection. The resulting recovery performance is most visible on a regression curve. Changes in the cutoff grade must also be taken into account to avoid unrealistic production targets. Estimation methods incorporating different mathematical assumptions and techniques may cause over-or underestimation of the grade and volume. If the selective ability of the mining equipment does not match the size of the reserve blocks, the performance will be compromised. The treatment plant efficiency, the throughput rate and the degree of bedrock clean-up also affect performance. The maximization of throughput does not yield the optimum results. Marine conditions, which are outside the operator's control, affect not only operational availability but also performance. Examples are provided from actual operations for various commodities, showing the relative magnitude of the different effects upon performance.

Jan 1, 1999

By D. J. Brunner, S. Mathur, D. McKinney

With the advent of faster micro-processors, the use of numerical methods to simulate complex fluid dynamic phenomena in three dimensions for use in design has become prevalent in the automotive, and turbo-machinery industries. The Computational Fluid Dynamics (CFD) method divides the region of interest into small control volumes which form the mesh representing the physical characteristics of the problem, and uses the finite volume method to intergrate the equations for the conservation of mass, momentum, energy and species over each control volume. Recent developments in CFD software expedite mesh generation, and enable the use of unstructured grids, comprised of tetrahedral volumes in three dimensions and triangular areas in two. CFD more accurately represents complex geometries and allows for relative movement of meshes enabling simulation of multiple moving bodies. 'ibis paper presents two examples of how CFD simulation can be used to assess mine and tunnel ventilation problems formerly addressed by application of analytical solutions which were developed assuming ideal incompressible conditions. CFD simulation is used to evaluate the impact of varying the airflow in a descentionally ventilated airway on the layering along the roof of smoke and hot gases resulting from a vehicle fire. Control of the smoke layer is required to enable safe egress from the vehicle, particularly if the vehicle is for personnel transport, and to ensure control of the fire contaminants throughout the ventilation system. The airflow required to prevent layering against the ventilation direction, calculated from the Bakke and Leach relations (Bakke and Leach, 1962), is compared with the CFD simulation results. An evaluation of the pressures, generated as a vehicle enters a tunnel portal, using CFD simulation, is also presented for unflared and flared portal configurations. These simulation results are compared with predictions derived using an analytical method which assumes one-dimensional and incompressible flow. Results of the CFD simulation are presented in an animated video format. SIMULATION OF BACKLAYERING In designing a ventilation system for a transit tunnel, the ability of the ventilating air to control and prevent backlayering of smoke and hot gases resulting from a vehicle fire is of prime concern. The buoyant nature of hot smoke causes it to rise relative to the colder, fresh air provided by the ventilation system. If the vehicle fire occurs in a descentionally ventilated tunnel, the smoke may tend to move upgrade in a layer above the incoming ventilation airflow. The layer may become thick enough to engulf a substatntial part of the tunnel cross-section upgrade of the incident that comprises the evacuation route. This effect is termed "backlayering' and it is similar to the development of methane layers in mines for which most studies related to backlayering have been done. Prediction Techniques Analytical A number of studies have been conducted (Bakke and Leach, 1962) to define the characteristics of this phenomena and as a result have produced relations which are used both in the mine and transit ventilation fields to define the air velocities required to control layering. In the transit industry the air velocity required to prevent the backlayering phenomena from occuring during a vehicle fire is called the "critical velocity" (Associated Engineers, 1975) and is dependent upon a number of factors: tunnel height, cross-sectional area and grade; ambient air temperature and density; and the heat release rate of the fire. Common practice in transit ventilation design is to provide an airflow which meets or exceeds the critical velocity. In order to determine whether or not the critical velocity can be achieved with a particular ventilation system, a one-dimensional simulation of the tunnel network is typically performed using programs such as the Subway Environment Simulation program (SES) originally developed in the late 1970's (Associated Engineers, 1980). The results obtained from SES are compared to the critical velocity to determine the adequacy of the ventilation system. Computational Fluid Dynamics For the backlayering simulations, a commercial CFD code which has been used successfully in a wide variety of engineering applications, was used. It provides numerous options for modeling laminar and turbulent flows, multiple turbulence models, definition of multiple species and chemical reactions between them, a variety of boundary conditions (including constant pressure and constant velocity inlets) and the ability to apply user-defined FORTRAN subroutines. It includes the ability to model conductive, convective, and radiative heat transfer. FLUENT also permits the use of "body-fitted coordinates" to match the computational mesh or grid to complex real-world geometries. Computational Fluid Dynamics Model The model developed to simulate the backlayering phenomena is comprised of an airway of rectangular cross-section, 4 meters wide, 4.5 meters high, and 200 meters long. A laterally

Jan 1, 1995

By Sergio Godoy P.

The Los Bronces porphyry copper deposit is located in the high Andes of Central Chile. Ore is mined from several tourmaline breccias and from an earlier porphyry. After years of experience in the geostatistical estimation of reserves in different zones of the ore body, we believe that success lies in considering the evaluation as an integrated process beginning with the analyses of the drilling density and sampling methodology, ending with the critically important reconciliation between the estimated and the actually extracted ore, in general, when errors or differences occur, focus is centered in the calculation stages of geostatistics. However, this paper demonstrates that all the evaluation stages are equally important and require the direct and continuous geologic input to ensure the best possible estimate within the frame of the geologic constraints.

Jan 1, 1992

By Steve Tadolini

Underground roof falls can have devastating effects on the safety of operations personnel, and equipment, and seriously impact production. Immediate steps are usually taken to danger off and secure the area while clean-up efforts are designed and implemented. A critical step, often overlooked due to production demand, is the determination of - why the roof fall occurred so that additional occurrences can be avoided in future developments or what measures can be taken to identify areas that have similar ?symptoms?? Forensic engineering includes the investigation of materials, products, structures or components that fail or do not operate/function as intended. The authors define forensics in ground control engineering as the study of evidence discovered while examining underground roof falls by applying expert observational techniques and established mining engineering principles to determine the probable cause, hypothesize solutions, and design engineering safeguards to prevent reoccurrences. Simply stated, the primary steps in the forensics of underground roof fall techniques are: ?Assess regional and local conditions prior to the event. ? Assess post-event conditions. ? Hypothesize plausible ways in which the pre-event conditions became the post-event conditions. ?Search for evidence that either denies or supports the various hypotheses. ?Apply engineering skill to relate the various facts and evidence into a cohesive scenario of how the event may have occurred. This paper details the proposed technique by utilizing a roof fall case study that required the examination of five primary factors: mine design parameters, excavation geology, method of excavation, method of support, and mining cycle times.

Jan 1, 2009

By Asa Weber

With continuing pressure from stockholders not only to maintain but to increase mineral revenues, producers have increased plant capacity. Depressed mineral prices have accentuated the trend toward higher production rates to maintain consistent cash flow, and these same trends have promoted the development of large-scale processing equipment. In addition to the need to handle increased throughput, larger flotation equipment can result in decreased capital-equipment and operating costs. The development of larger column and conventional flotation equipment relies, in part, on suitable scale-up procedures. To properly scale-up large flotation cells and columns, certain constraints and design parameters must be taken into consideration, including velocities in the vessel, residence time, solids suspension, and lip loading. This paper will review the design constraints and scale-up criteria for WEMCO® flotation cells. Scale-up criteria are augmented with computational-fluid- dynamics analyses and high-speed imaging techniques, as well as multiple regresesion analysis of in-plant operational data.

Jan 1, 1999

By F. Qiming

By means of flotation experiments, potential-pH diagram, electrochemical testing and X -ray photoelectronic spectrum (XPS), the main factors (the thermodynamics and the property of surface products) influencing the separation of sulfide minerals (such as galena and chalcopyrite) in the collectorless flotation are studied. The actual conditions (Eh, pH) of separation are not conformable to the results of thermodynamic calculation. The kinetic behavior of oxidation of sulfide minerals and the property of oxidation products are the decisive factors of the separation of sulfide minerals in the collectorless notation.

Jan 1, 1992

By R. V. Ramani, K. V. K. Prasad

Forecasting mined grade variability from exploration information is a challenging task in mine planning. For effective planning of activities, such as workplace scheduling, ore grade quality control, etc., development of realistic numerical simulation models of in situ variability from exploration information is an essential first step. Geostatistical conditional simulation (GCS) is one of the well known methods to develop such simulations. Recently, stochastic fractal models based on the assumptions of scale-invariance and self-similarity have been used for developing simulations of several natural phenomena. It has been suggested that these models might permit the generation of short-scale variability information from exploration data with greater fidelity when the data satisfies the attendant assumptions. In this paper, stochastic fractal models are reviewed, and their relationship to geostatistical variogram models is examined. A comparison of the two simulation techniques has been performed using coal sulfur data from a mined-out coal property. The results of this comparative analysis are also presented in the paper.

Jan 1, 1993

By Chien D. Ngo, Andre Bachmann, Rainer Bunge

The remediation of contaminated sites has gained great importance in many industrialized countries. One method for cleaning the polluted soils from such sites is "soil washing," the scope of which is the separation of the contaminants from the soil. Soil washing is an outstanding example for a successful transfer of technology from Mineral Processing to Environmental Engineering. This presentation intends to introduce the Mineral Processing Engineer to soil washing through a short review of the fundamentals, and the discussion of an example for a successful soil cleaning operation in Switzerland.

Jan 1, 1995

By L. R. Stoiser

The mineral resource potential of the Los Bronces deposit was successfully evaluated by an intense, coordinated field program over a 37-month period (April 1978 - May 1981). This project was part of a much larger study to determine the economic feasibility of expanding the open-pit, mine-mill operation 10-fold to 80 kt/d (88,000 stpd). The resource project included more than 120 km (74 miles) of core drilling and 64 km (40 miles) of drill rig access way construction under adverse topographic and climatic conditions, detailed geological mapping, and other related activities. The Los Bronces deposit is composed of an earlier mineralized porphyry-type body intruded in part by a large complex of mineralized hydrothermal breccia pipes. The mineralization is hosted by intrusive and extrusive igneous rocks. Various stages of erosion, oxidation, leaching, and supergene enrichment of copper are present. Drill hole indicated geologic reserves are estimated at 1.3 Gt (1.4 billion st), averaging 0.81% copper and 0.016% molybdenum at a cutoff grade of 0.6% copper equivalence decreasing to 0.25% over the life of the mine. Trace amounts of silver are also present.

Jan 1, 1987

By Charles P. Lazzara, Alex C. Smith, Mark W. Ryan

The U.S. Bureau of Mines developed an experimental method to evaluate the relative effectiveness of water additives on the extinguishment of coal fires. The experiments were conducted in the fire zone of the multiple entry section of the Bruceton Experimental Mine. Chambers filled with one hundred and eighty kilograms of Pittsburgh seam coal were ignited and allowed to burn until well developed fires were achieved. Extinguishing agent-water solutions were then applied to the fires and the quantity required to extinguish the fires compared to the amount of water alone required to extinguish similar fires. A 20% diammonium phosphate-water solution required an average of 22 L to extinguish the coal fires, while two commercially available additive-water solutions required an average of 30.6 and 30.3 L, respectively. The average amount of water required to extinguish the fires was 28 L. An analysis of covariance, using the thermal energy of the coalbed, Q, to quantify the fire at the time of extinguishment, showed that the diammonium phosphate-water solution was slightly more effective at extinguishing these coal fires than water alone, while the two commercially available additive-water solutions were statistically equivalent to water alone.

Jan 1, 1992

By G. D. Elliot, R. L. Grayson, G. L. Winn

For the years 1990 and 1991, West Virginia's underground coal small-mine fatality rate was approximately 10 times higher than the national coal-industry fatality rate. Although the number of fatalities went down from 22 in 1991 to 17 in 1992, West Virginia still led the nation in coal-mining fatalities. A team of mining and safety professionals from West Virginia, interfacing with the Mine Safety and Health Administration and the West Virginia Office of Miners' Health, Safety and Training, studied this problem. A clear path for formal intervention was determined and is presented here.

Jan 1, 1996

By Qing Wang

Open pit mines require substantial capital investment at the beginning of the operation and replacement investment at later years. The objective of obtaining the highest possible return on investment in a mining project can only be achieved with an efficient long term production plan. This plan consists of optimally determining four principal elements: 1) the amount of ore and waste to be mined each year, 2) the specific blocks to be mined each year, 3) the optimum mine life, and 4) the ultimate pit limits, which delineate the total reserve to be mined. The existing methodologies only provide solutions to one or two elements, by assuming the others known. Furthermore, the cost of mining each block in the deposit is assumed to be known and independent of the production schedule. The four elements of production planning are interrelated and the cost of mining any block is a function of the production schedule. The ultimate goal of this study, ,whose first steps are' discussed in this paper, is to develop a solution methodology that can simultaneously optimize all four elements of the production planning problem in open pit mines without making a priori assumption on any of the four elements.

Jan 1, 1992

By S. A. Voltura

The Phelps Dodge Miami smelter has smelted copper concentrate using the ISASMELT technology since 1992. The design throughput rate was 591,000 tonnes/year and after a slow start-up, the production rate has exceeded the design after the seventh year of operation. In 2002, the smelter consumed 719,000 tonnes of copper concentrate and has the potential to hit the permitted rate of 772,000 tonnes/year. Improvements to the smelting vessel and the surrounding support processes have allowed for continuous improvement from start up until now. This presentation will outline the chronological events and the improvements completed to accomplish these improvements

Jan 1, 2004