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By Johann Engelbrecht, Stéfan de Bruyn, Petrus van den Heever

A system for the on-stream X-ray diffractometric determination of mineral phases in slurries was developed in response to the mining industry's need for process control during the beneficiation of industrial minerals. The instrumentation for and results from testwork conducted at a phosphate rock beneficiation plant in Florida are discussed. Results show that the concentrations of the minerals apatite (var. francolite) and quartz can be accurately determined every few minutes, so that adjustments to the flotation circuit can be timeously executed from the control room. The on-stream measurements can ultimately be integrated into an automated plant control strategy. Estimates of savings on reagent and staffing costs, as well as the benefits from consistent grades and greater recoveries, have shown that the investment in such a system could often be recovered in less than a year.

Jan 1, 1999

By S. G. Malghan

Flotation circuits of a range of complexity are in use for a large number of ores. Since each ore is different and end-product quality requirements are not necessarily the same, circuit configurations of varying complexity are designed. How- ever, certain basic types of circuit configurations can be identified based upon the flotation behavior of the ores. These basic types can be combined to develop the specific f lowsheet configurations for a given ore. This chapter begins with a brief discussion of basic flowsheet configurations. Examples of the flowsheet configurations for a number of specific ores bearing different minerals are then described.

Jan 1, 1986

By B. Elevli, M. D. G. Salamon

Production scheduling of an open-pit mine is one of the most important steps in open-pit mining. The mine's production schedule defines the distribution of cash flows and, as a result, directly influences the net present value (NPV) and overall economic feasibility of a project. The need to plan and operate a mine with an optimum production schedule has been obvious for some time, but the methods used to obtain such a schedule have not been so obvious. The current practice is to do a trial and error analysis by hand. In an attempt to improve the way production scheduling is currently done, a new computer based production scheduling algorithm was developed. This paper describes the fundamentals of this newly developed heuristic scheduling algorithm and its application to a gold deposit. The results of this case study show that the schedules, based on the new method, provide improved cash flows compared to production schedules done manually.

Jan 1, 1992

By F. Djahanguiri

The US Bureau of Mines con¬ducted research on underground stope leaching of metalliferous ores. Leaching underground would minimize the environmental impact of ore processing on the surface and would maximize minable reserves. An important aspect of this process is the minimization of pregnant solution losses and groundwater contamination by leach solutions. Bulkhead design and construction are important issues for solution control and stope-leaching economics. A reinforced-concrete bulkhead was designed, constructed and tested for solution control in an underground mine near Idaho Springs, CO. This paper presents the bulkhead-design methodology and construction procedure.

Jan 1, 1997

By F. M. Swain

High-calcium limestones occur in the upper part of the New Market Formation, of Lower Middle Ordovician age, in Franklin and Cumberland Counties, Pennsylvania. The high-calcium facies of the New Market Formation is represented by sublithographic limestone or vaughanite, which probably formed in quiet water; low-energy environments such as intershoal lagoons, or in protected bays similar to the present-day Florida Bay environment. Rapid facies changes are characteristic of the strata. The better grade of stone lies in the upper 100 to 125 feet of the New Market Formation and averages 95-97% calcium carbonate. Silica and magnesia are about equal in amount as impurities. One high-calcium belt extends from the Maryland state line through Chambersburg and Newville to beyond Carlisle. The strata in this belt are structurally complex, which requires careful field study' and core-drilling prior to exploitation. Stone suitable for blast-furnace flux is present in relatively large amounts, but stone for open-hearth use or portland cement requires more selective quarrying.

Jan 1, 1966

As discussed previously, total cost is the sum of the direct materials, direct labor, and production overhead costs. The assignment of direct materials and direct labor costs to individual activities is generally straightforward. The assignment of overhead often is not. Overhead costs frequently contain allocations that only approximate the demand the activity has made o; the overhead resources. The inaccuracy of the overhead calculation can create erroneous production cost information and lead to suboptimal management of the operation. This problem is particularly acute when determining the production cost of individual products in multiproduct firms. Pricing, process management, and product mix decisions are especially susceptible to errors in product costing. The problem of properly determining production cost is complicated by the fact that few if any alternative methods exist to identify the inaccuracies in overhead allocation. To avoid errors, some firms simply ignore overhead costs in their product cost calculations, particularly those resulting from marketing and distribution of the final product.

Jan 1, 1999

By W. X. Wang, O. Stephansson

In the mining and quarry industries, rock fragments are often transported by conveyor belt. To estimate the qualities of the rock fragments (i.e., size distribution and shape), an operator must take samples from the conveyor and manually perform a sieve analysis, which is time-consuming and tedious. Alternatively, an image-analysis system can be used to monitor the fragment quality on a fast moving conveyor belt. However, images of fragments on a fast moving belt vary to such a degree that the quality of any two successive images are not the same, and some of the images are of such poor quality that they are unrecognizable by human eyes. If poor-quality images are directly analyzed by a segmentation algorithm, the analysis will not be satisfactory. To resolve this problem, it is necessary to use an image-classification program for the automatic selection of fragment images with good quality. Because of this need, an image-classification program was developed and tested both in the laboratory and in the field Testing of the system on different types of fragments showed that the system works reasonably well.

Jan 1, 1997

By D. J. Shields

This paper describes a dynamic short-nun mineral supply model that incorporates secondary processing, transportation, mineral market structure, and direct mining and milling costs. The method employed is network flow programming. Empirical tests utilizing domestic phosphate industry data have been conducted by the Bureau of Mines, U.S. Department of the Interior. In the model, nodes represent physical locations such as a mine or port. Arcs represent either a process, such as mining, or movement, such as rail or barge transport. Each arc is described by lower or minims allowable flow bounds, upper or maximum possible flow bands, and variable cost. Mines and previous period inventories represent potential supply. The model is optimized via a cost minimizing algorithm, which attempts to fulfill stated total demand at the minimum possible system cost given the arc constraints. An optimal solution of the model will predict production patterns by mineral property for each prespecified level of demand. A mineral property is defined as a separate accounting entity such as a mine. The results of serial optimizations are used to construct the short-run supply curve. Dynamic policy analysis can be conducted by altering the arc constraints.

Jan 1, 1986

By John K. Hollmann

The use of the direct method of determining coal methane content has grown in the last decade from a research technique into a practical coal exploration tool. However, the literature available on the subject is somewhat lacking in site-specific guidance and observations on the conduct of the method and the use of the resulting data. This study discusses some practical lessons learned in conducting a large scale direct measurement project at an operating mine, describes the initia1 interpretations and uses of data from the project, and presents observations from subsequent mine operations into the success and limitations of using direct measurement data in mine planning. The site studied is in central Pennsylvania on the Appalachian Plateau and includes coal seams in the Allegheny series.

Jan 1, 1987

By Boris M. Vorobjev

The paper in question discusses a wide range of topics on the coal mining environment in general and on computerized coal mine environment systems in particular. The emphasis is being made on methodological aspects of coal mine environment with reference to computerized monitoring systems Classification of computerized coal mine environment monitoring system is suggested by the author with specific reference to coal mining operations. Coal quality control system at all levels (coal face to regional levels) is also discussed briefly hereunder, since coal quality is one of the major factor for environmental management. An integrated coal mining economic and environmental management super-system is presented in this paper Review Of the UN/DTCD, UNDP European Regional project "Computerized Coal Mining Systems" is presented here. Conceptualization of a new European Regional project on Coal Mining Environment and Economic Management is also a topic discussed in the paper.

Jan 1, 1992

By F. W. Petersen

In the precious metal industry, activated carbon is used extensively for the recovery of gold and silver from cyanide solutions, particularly from slimy pulps and unclarified solutions. However, carbon can easily become fouled by inert particles in the pulp, thus decreasing the activity or gold loading of the carbon. This paper attempts to quantify the distribution of fine inert particles in activated carbon. Furthermore, a possible mechanism for the intrusion of fines will be postulated. Precipitated silica and ground silica sand were used to simulate pulp conditions and their loadings on activated carbon were determined by ashing. The kinetics of intrusion of fines into the pores of carbon were relatively fast, and were dependent on the concentration in the pulp. Results indicated that particle size of the solids and zeta potential of the fines influenced the loading of inert species on carbon. Scanning electron microscopy and secondary ion mass spectrometry showed a decrease in solids concentration to the centre of the carbon particle.

Jan 1, 1995

By Haydn H. Murray

The three major catalyst markets that utilize industrial minerals as raw materials are petroleum refining, chemical processing, and emission control. Because of economic, competitive, and regulatory pressures, catalyst producers are pushed to develop products with improved performance to meet changing environmental standards. Also, refiners are demanding new families of cracking catalysts that will crack residual fuels. In 1987, worldwide cracking catalyst sales amounted to $457 million (Occelli, 1988a). Recently enacted federal and state laws to improve air quality have prompted strong growth for environmental catalysts, which in 1989 accounted for more than a third of the $1.9 billion catalyst market in the United States (Farrauto, Heck, and Speronello, 1992). A catalyst is a material that promotes or enhances a chemical reaction but does not itself enter into the reaction. One of the more important mineral groups used as catalysts is clays. The first recorded use of clay as a catalyst was its use in the dehydration of alcohol (Bondt et al., 1797). Clay minerals that are used as catalysts are kaolinite, halloysite, smectite, palygorskite, and sepiolite. Minerals used as catalysts, catalyst supports, or as a raw material to make zeolites are kaolinite, halloysite, sodium montmorillonite, calcium montmorillonite, hectorite, palygorskite, sepiolite, talc, calcined kaolinite, gibbsite, chlorite, and titanium dioxide.

Jan 1, 1994

By A. C. Noble, D. E. Ranta

Orebodies with intricate three-dimensional shapes (such as porphyry molybdenum deposits) are difficult to model using geostatistics or other computer-assisted methods. The strong trends in their spatial grade distributions occur as mathematically complex shapes and prevent the customary assumption of local stationarity that is required for accurate ore reserve estimation. "Zoned Kriging", a new method developed by AMAX, solves this problem directly by using the geologist's interpretation of the ore zones as a parameter in the kriging equations. The geological basis and methods used in the Climax ore zoning technique are reviewed and discussed relative to their application in zoned geostatistical modeling. The Zoned Kriging technique is described and demonstrated using data typical of mineral deposits.

Jan 1, 1992

By Danqing Xu, A. W. Khair

This paper presents an analysis of mechanism of secondary fragmentation and respirable dust generation due to regrinding. In continuous miners, the recovered coal and uncleaned coal from the previous cutting cycle have to be transported through the circumference of the cutting drum, subjecting the coal to regrinding. Such regrinding comminutes the coal material utilizing kinetic energy, thus creating a great amount of respirable dust. The mechanism of a single particle subjected to regrinding is analyzed. A mathematical model is developed to describe regrinding in field conditions. The important factors influencing the comminution process are discussed in detail. Utilizing three types of coal seams, laboratory experiments are being carried out with an Automated Rotary Coal Cutting Simulator (ARCCS) to quantitatively evaluate the effects of some particular parameters, such as cutting velocity, depth of sump and properties of coal material, on breakage and on the amount of respirable dust generated. An orthogonal fractional factorial experimental arrangement is used to optimize experimental design. Preliminary experimental results are presented.

Jan 1, 1991

By H. Bernatowicz

The Nucoalyzer (On-Line Nuclear Analyzer) is a new method recently made comercially available for monitoring the elemental composition of a process stream. Applications for the Nucoalyzer include grading ore on a conveyor belt before or after it has gone through primary crushing, monitoring the slurry being transported in a pipe to the concentrator, and monitoring the stream of concentrate or the tailings from the concentrator. The Nucoalyzer may also be used at the smelter to monitor elements in the feed that include copper, sulfur, iron and silicon where a uniform feed is desired. The advantage of the Nucoalyzer over most other techniques are (a) it performs the measurement directly on the process with no sampling necessary, (b) the analysis can be performed on streams of particulate and slurries, and (c) the system does not have to make contact with the material it measures. These Nucoalyzers are operating at coal fired power plants and several more are about to be placed in service. This paper discusses the principles of operation of the Nucoalyzer, our experience in the field, application of minicomputers to data reduction, and potential applications in the ferrous and non-ferrous industries.

Jan 1, 1982

The processing capability of a semi-autogenous (SAG) mill is greatly affected by ore geology and operating variables within the mill. The SAG mill is problematic because it cannot be conveniently studied on a smaller, laboratory-scale mill. The interior of the mill, where grinding takes place, cannot be observed using instrumentation available today. Yet the motion of the rock and ball charge determines the power draft and hence capacity of the mill. Therefore, mill optimization is pursued with a charge motion simulation software. This software uses the discrete element method to describe the individual motion of numerous ball and rock particles in the mill. It is shown that by simply increasing the chord length between the lifters and increasing the face angle of the lifters the capacity of the mill can be increased. Such a configuration of lifters allows the operator to increase mill speed, hence drawing higher power while considerably minimizing direct ball strikes against shell plates and lifters. A case study of a 36 ft. diameter x 15 ft. long mill is presented. Reducing the direct ball strikes leads to lesser steel consumption both in terms of balls and lifters.

Jan 1, 2000

By Kenneth N. Han, Xinghui Meng, A. J. Monhemius, G. W. Warren, E. Peters

The leaching of gold in ammoniacal solutions containing various oxidants in an autoclave has been investigated. Also studied are thermodynamic and kinetic aspects of the ammonia leaching of gold and silver. The variables studied included stirring speed, temperature, concentration of ammonia, ammonium, and various anions. Arrhenius activation energy values were found to be between 47.1 kJ/mol and 86.2 kJ/mol depending upon the kinds of oxidants used. An electrochemical reaction controlling mechanism has been proposed for the dissolution reaction. The leaching behavior of gold and silver from various ores in ammoniacal solutions containing various oxidants has also been investigated. The samples tested included sulfidic as well as carbonaceous refractory ores. The recoveries of gold and silver from these refractory ores were better than 96% within 2-3 hours of leaching time.

Jan 1, 1993

By D. Bizier, B. H. Gardner, Y. P. Wang, S. Serata

As part of an ongoing effort to develop more cost-effective and “user friendly” hardware for geomechanical measurements required for underground mine design, Serata Geomechanics, Inc. (SGI) has investigated the potential of borehole pressure cells (WCs) for in situ measurement of stress states and continuous monitoring of changes in ground stress. In particular, because of certain advantages gained thereby, WCs utilizing an elastomer, instead of metal (e.g., copper), for the skin of the pressure cell have been developed. A data analysis technique for determining ground stress state directly from BPC data has been developed. This technique has been tested for salt ground through both in situ applications and computer simulation analysis of the BPC/borehole boundary interaction. This paper discusses the data analysis technique, the results of field and computer simulation testing of its validity, and evaluates the advantages of elastomeric BPCs in relation thereto. It utilizes field data from recent elastomeric BPC applications in the salt mine at Goderich, Ontario operated by the Sifto Division of Damtarn Inc.

Jan 1, 1986

In his keynote address at the 18th International Minerals Processing Conference (IMPC), R.P. King, director of the University of Utah Comminution Center, said "it will be the application of very fundamental physical principles that is likely to bring major advances in comminution technology (IMPC, pp. 39-45)." It is evident from the literature published in 1993 that many of these fundamental studies, particularly as they relate to single-particle fracture mechanics and mineral liberation, are starting to bear fruit. The beginnings of fundamental mathematical models for design, scale-up and control of comminution systems are now taking shape. Modeling/fundamentals Population balance models (PBM) have been used to describe grinding systems for 20 to 30 years. However, Williams and Meloy (IMPC, pp. 73-79) pointed out some of the inherent problems with this modeling approach and that there is no unique solution for the unconstrained PBM for grinding. Many of the current constraints used to back-fit selection and breakage functions were also shown to have problems. The need for a more fundamental means of determining these parameters was indicated.

Jan 1, 1994

By William J. Francart, Edward J. Miller

The utilization of computer based monitoring systems for fire detection in underground coal mines has grown significantly in the past seven years. In 1984, an annual MSHA survey identified a total of 38 systems being used in U.S. underground coal mines, while a 1990 survey indicated the number has risen to 112. The applications for mine monitoring have also changed according to the annual surveys. From April 24 to June 21, 1990, investigations were conducted by personnel of the Ventilation Division, Pittsburgh Health Technology Center, in cooperation with Coal Mine Safety and Health, concerning the installation and operation of Atmospheric Monitoring Systems in underground coal mines. These investigations were conducted to gather information concerning the ability of the AMS to detect fires and heatings, false and nuisance alarm frequencies, information related to system maintenance, and information related to employee training on system operations. This paper addresses current applications of the systems, fire and heating identification rates, application of systems in dieselized coal mines, system maintenance, and employee training requirements. While deficiencies were identified in some applications, results of the studies and survey indicate the use of atmospheric monitoring systems can be effective in identifying mine fires and heatings.

Jan 1, 1991