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By Brij M. Moudgil, Shoulian Zhu, J. L. Pinault

A new technique, prompt neutron activation probe (PNAP), for analyzing phosphate rock slurry in-situ was evaluated both in the laboratory and at the plant. The technique yielded a high precision in the analysis of Ca, Si and H using 252Cf source. Low accuracy of the direct measurement of P using 241Am/Be in the laboratory tests was attributed to the interference of rare earth elements present in the samples, particularly Gadolinium. No significant effect of variables such as solids loading, particle size distribution, and flotation reagents was observed on the probe performance. The probe can detect the compositional changes of the feed, tailings and the concentrate streams in the plant.

Jan 1, 1993

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 Jürgen Lotze

Previously (1981), it was shown that the fiscal policy practised by some IBA-member countries is mainly responsible for a significant shift of known bauxite resources into higher processing-cost categories. The possible impact of politically imposed fiscal costs on the competitiveness of relevant bauxite resources is investigated in detail by means of a model calculation procedure.

Jan 1, 1984

By R. J. Sweigard

Many states are considering the need to establish or modify policy relating to the disposal of coal ash. One of the primary concerns is the impact of leachate from the ash disposal sites upon groundwater and nearby bodies of surface water. A detailed site investigation was conducted at a coal ash disposal facility associated with a power generation station. The disposal site is situated alongside a major river. Monitoring wells were installed and soil samples were taken for characterization. Groundwater models were used to simulate migration of leachate from the disposal site toward the river. Such models have the potential to be used to verify regulatory compliance. This paper addresses the validation and adaptability of these models to this case and their usefulness as possible tools to be used in future environmental audits.

Jan 1, 1993

By A. Ligorio Pires de Carvalho

The main potash deposit at Taquari-Vassouras is contained in cycle VII, and consists of several sylvinite bodies. Cycle VII belongs to a sequence of nine cycles defined by Szatmari (1974) in the Sergipe-Alagoas basin. The sylvinite layers are separated by halite beds. They are seated on or may be laterally in discordant contact with other lithologies such as the tachyhydrites at the base, and the limestone breccia at the top. The main structural features in the deposit include numerous synclines and anticlines, salt dissolution phenomena, and open fractures associated with the axes of the anticlines.

Jan 1, 1995

By R. C. Bunge

Many minerals float best with fatty acids in the intermediate pH range. For example, fluorite, a semi soluble salt mineral, exhibits a maximum contact angle and a maximum flotation recovery in the pH range of 6-8 after conditioning in a palmitate solution (fig. 1). The maximum in flotation coincides roughly, as many researchers have observed, with the boundary of bulk precipitation of the fatty acid. According to fig. Z this boundary is in the above case of 5xl0-7 M palmitate approximately at pH 6.3. For assessing the phenomena occurring at the bulk precipitation boundary of fatty acids, the surface tensions of carboxylate solutions have been measured under various conditions. Fig. 3 shows the surface tension development of palmitate and myristate solutions of increasing concentration at pH 12. Also shown are the bulk precipitation edges (BPE) of the respective solid species that is stable under these conditions, that is the potassium acid soap, HKAZ. Both curves display a similar behavior. As the concentration of carboxylat,e increases, the surface tension decreases, until a minimum is reached at which the curves level off. The decrease of surface tension with increasing carboxylate concentration is generally taken to indicate the surface excess of the carboxylate ion. The point where the curve suddenly levels off has not yet been explained. While it is well known that the onset of micellization (CMC) may cause such an inflexion of the surface tension curve, this cannot be the case here because the position of this point depends, as shown in fig. 4 for palmitate, on pH (the CMC is generally independent of pH). We believe that this point indicates the precipitation of a colloidal acid soap (colloidal precipitation edge, CPE) before the bulk precipitation of this species sets in (BPE).

Jan 1, 1994

By D. E. Ranta, M. G. Schulz

Mining of Molybdenum at Questa, New Mexico has been accomplished by block cave methods since August, 1983. As caving progresses, a periodic geologic evaluation is made of the rock types present in finger raises on the Grizzly Level of the mine. The production maturity of the cave can be monitored by relating this data to geologic cross-sections through the orebody. The draw point mapping program is a simple and effective tool that is used in making draw control decisions at Questa.

Jan 1, 1992

By Henry P. Cole, Andrzej M. Wala

Engineers and psychologists at the University of Kentucky have developed simulation exercises that teach and test proficiency of mining technical personnel for coping with planned and accidental connections between separate air courses in underground mines. The exercises are based upon investigations of actual mine disasters. The exercises are judged as valuable and interesting training materials by experienced mining personnel. Although these specialists generally perform well on the exercises, potentially fatal errors are not uncommon. The use of such realistic exercises may better prepare miners for preventing and coping with underground mine ventilation emergencies.

Jan 1, 1987

By T. J. van der Walt

This paper proposes a new methodology to model ill- defined processing operations using neural nets (NN's). A process with many variables (large dimensionality) cannot be modelled adequately if limited process data are available. This problem of multi-dimensionality is addressed and an approach suggested to reduce the dimensionality using NN's. The result of this modelling methodology is a combined model of phenomenological expressions and NN's. The model can successfully be incorporated in a dynamic simulator of the process. A new approach to conduct modelling on the basis of continuous data collected directly from an industrial processing unit, is also proposed. The modelling methodology is applied to a typical processing operation, the resin-in-pulp (RIP) process.

Jan 1, 1992

By Paul H. Lu

This paper proposes a novel method, "integrity factor approach," of mine-pillar stability evaluation based on in situ triaxial-loading measurement. The pillar integrity factor is defined as the quotient resulting from division of integrated total pillar strength across the critical dimension by the integrated total pillar load across the same dimension. The integrity factor is dynamic, while the conventional safety factor is static. With this approach, the pillar stability can be evaluated at any stage of mining progress during panel operation. It automatically considers the progressive failure of the pillar and post-failure strength without the need to clearly define the boundary between yielded and intact zones of the pillar. Based on two case studies, the integrity factor approach is shown to be a practical, effective technique for evaluating stability of conventionally designed pillars. It is suggested that a more realistic estimate of in situ pillar strength could be made based on the combination of in situ triaxial-loading measurements and laboratory true triaxial compression tests, rather than through the traditional combination of biaxial-loading measurements and conventional triaxial compression tests.

Jan 1, 1986

By H. Zhu, A. G. Journel

Qualitative and interpretive information as obtained from geological and/or geophysical studies, in addition to precise measurement, is incorporated into the estimation process through an indicator variable. The indicator conditioned estimator is formulated as a cokriging, and its expression is data value dependent as opposed to that of the traditional kriging estimators. The solution of the dual cokriging system provides simultaneously an estimate of the unknown and an estimate of the conditional probability that the unknown belongs to a specific population or class. Being an unbiased and minimum-error-variance estimator by construction, the indicator conditioned estimator is better in the least square sense than the ordinary kriging estimator because it uses additional information carried by the indicator data. A case study using a large reference database is presented; the indicator conditioned estimates have a smaller conditional bias and a smaller error variance than the ordinary kriging estimates. The results also showed that the indicator conditioned estimator is more efficient for selection in mining.

Jan 1, 1990

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 Chester R. McKee, Amar C. Bumb, Kohei Kawakita

Unlike many other heavy metals, gold can be profitably mined in small operations because of the prices. One mining technique that seems ideally suited for small deposits of gold and for certain large, lowgrade oxidized disseminated deposits is solution mining. Solution mining generally requires lower capital investment and operating costs than conventional mining and milling and is safer and less degrading to the environment. Although gold has long been recovered by cyanide leaching following conventional milling, solution mining as discussed here gained momentum only in the past two decades, during which time alternative lixiviants instead of cyanide have been researched. Chamberlain and Pojar (1981) classified solution mining systems used today as three types, namely heap, dump, and in-situ leaching.

Jan 1, 1990

By D. R. Nagaraj

Literally thousands of new flotation agents, both collectors and modifiers, have been proposed for sulfide and non-sulfide flotation over the past six decades since the beginning of the use of soluble surfactants in flotation. In stark contrast, the number of flotation agents used in practice is small. Xanthates and fatly acids, along with a few well-recognized modifiers, dominate the industry. Three major questions will then arise: a) are there truly specific needs in the industry that call for chemistries that are different from those used currently ? b) if yes, given the track record in the industry, what is the likelihood that such different chemistries will ever be used and to what extent ? and c) is more research into developing new chemistries necessary ? A critical assessment of flotation agents in general is made in this paper to provide answers to these questions and to identify the major factors that are responsible for the large disparity that exists between flotation reagent research and commercial usage.

Jan 1, 1994

By Bill Sayer

Cadman, a wholly owned subsidiary of Heidelberg Cement, is a leading supplier of sand and gravel as well as ready mix concrete in the greater Seattle area in western Washington State. Cadman's aggregate mine is located in North Bend, 34 miles east of Seattle, WA, and consists of a "Lower Pit" and an "Upper Pit." In 2005, Cadman planned the upgrade of the North Bend mine operation as follows: Upper Pit (Figure 1): 1. Crushing Plant, Stacker and Stockpile 2. Storage Reclaim Belt Feeders 3. Feed Conveyor 4. Downhill Overland Conveyor Lower Pit (Figure 2, Photo 12): 1. Radial Stacker 2. Storage Reclaim and Truck Load-out

Jan 1, 2008

By D. M. Hausen

The role of applied mineralogy in mineral beneficiation begins with early prospect evaluation, and continues through stages of amenability testwork and pilot plant studies to the ultimate development of viable processes for mineable orebodies. After plant construction, mineral products from various locations, i.e., grinding circuits, flotation cells, gravity circuits, kilns, smelters, etc., require quick identification and control monitoring for optimum efficiency and recovery. Ore/gangue minerals are identified, quantified, and textural associations investigated by microscopic, spectrographic, and electron-optical instruments. Mineralogic analyses of large numbers of samples have required the development of sophisticated computer systems that merge analytical and mineralogic data into useful diagnostic data bases

Jan 1, 1991

By Rogério C. Guimarães, Antonio E. C. Peres

Arafertil's oxidized ore presents barite grades that oscillate between 5 and 12%. The barite separation plays a major role in the production of apatite concentrates for the manufacturing of phosphate fertilizers. The selectivity, via flotation, in the system barite-apatite is inherently difficult due to the similarity of the physical/chemical characteristics of these minerals. The evaluation of the relevant aspects of this separation was performed based on the determinations of the electrical surface charge of barite and apatite, the abstraction isotherms of cetyl-stearyl sodium sulfate and fatty acids soaps for barite and apatite, microflotation in a modified Hallimond tube, and flotation tests in a batch column. The results showed that the adsorption of cetyl- stearyl sodium sulfate occurs preferentially onto barite, in comparison with apatite. On the other hand, the rice bran oil soap presents similar adsorption levels onto both barite and apatite. The cetyl-stearyl sodium sulfate was selective as a barite collector in the presence of apatite, a fact that was not observed in the case of rice bran oil soap.

Jan 1, 1999

By R. Lindsay Mundell

During the past 12 years, use of longwall methods to mine coal in the United States has continually in- creased. Although these methods offer several advantages, health hazards often exist because of unique and difficult problems in the control of respirable dust. This paper discusses the results of respirable dust studies conducted on United States longwall mining operations in 1972and 1978. Current engineering control methods (ventilation, water application and use of machine cutting parameters) and administrative controls for minimizing employees' respirable dust exposures are discussed.

Jan 1, 1980

By D. W. Park

The Longwall Strata-Control and Maintenance System (LoSCo-MS) is a software and data-communication system developed at the University of Alabama. This system integrates real-time shield monitoring, data presentation, analysis and the forecasting of forthcoming events. The main objective of this system is to provide stability information on longwall panels, including excessive shield load, low setting pressure, leg leakage, poor shield performance and imminent maintenance problems. Analyses of various mining and geological parameters were also performed to determine past and present roof characteristics and to forecast roof loading patterns for the following mining cycles, the next periodic weighting, etc. A local coal mine in the Warrior Coal Basin has adopted this system to provide daily evaluation of ground stability and maintenance problems in their longwall panels. Two years of experience with this system is covered in this paper.

Jan 1, 2000

By Raymond E. Riethmann

El clasificador de espiral fue diseñado originalmente para circuitos cerrados de molienda. Desde entonces se ha aplicado con éxito a otros trabajos de clasificaci6n donde se necesita realizar un corte de dos productos. Inherentemente a las cualidades especiales de este cla- sificador está especialmente preparado para: clasificar, lavar, o agotar materiales tales como minerales, roca fosfática, arenas, carbbn, conchas de ostra y sales fosfáticas. Presentamos ahora las características de operation, flexibilidad de diseiio y líneas maestras para una apropiada aplicación.

Jan 1, 1982