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By J. E. Murphy, R. Y. Wan, K. R. Sandgren, M. C. Fuerstenau

As part of a U.S. Bureau of Mines program to evaluate alternatives to sodium cyanide in gold leaching, three organic nitrile compounds were tested for their effectiveness as gold lixiviante. The organic compounds examined were malononitrile, acetonitrile, and cyanoacetamide. The reagents were tested on an oxide ore, two carbonaceous ores, and a eulfidic ore. Acetonitrile and cyanoacetamide were shown to be ineffective gold leachante. Malononitrile was the most successful of the organic lixiviants. On an oxide ore, malononitrile performed shilarlyto sodium cyanide with extractions of around 80 pct. For carbonaceous "preg-robbing" oree, sodium cyanide was completely ineffective while malononitrile extracted 24 pct of the gold. When using a resin-in-leach technique, extraction with sodium cyanide increased to 60 pct and the extraction with malononitrile increased to 80 pct. On the sulfide ore, sodium cyanide and malononitrile performed similarly with 80+ pct extraction as long as the pH of the malononitrile solution wae maintained above 10.5. Malononitrile is six times less toxic than sodium cyanide as measured by LD, levels. Therefore, malononitrile has a significant advantage over eodium cyanide, but its high cost and undemonstrated usefulnees make it unlikely to gain acceptance.

Jan 1, 1993

By F. L. Wilke

In the german hard-coal mining industry the mechanization of longwall faces and the machinery used for the extraction process have reached such an extent, that an extensive increase in productivity and face performance is not likely to be expected. At present, the greatest amount of man-shifts is needed for operations such as tunneling, transportation and haulage (fig. 1.). The most restrictive parameter, especially considering the possible ad- [ ] vance rate of faces, is the comparatively low advance rate achieved in drifting operations. Therefore improvements in productivity and advance rates of drifting operations will have considerable influence onto the extraction rate of the faces. The importance of drifting operations - and especially the so-called "conventional drifting by drilling and blasting" within the scope of long- term planning strategy of the german hard-coal mining industry is reflected by the development factor. This factor is given by the ratio: cubic meters of rock excavated in drifting per 1.000 tons saleable coal produced. In 1973, which is considered to be the beginning of the oil-crisis, this factor was determined to be 17.7 m3/ 1.000 tons sale- able coal.

Jan 1, 1982

By Patricio A. Espinoza, Aldo Casali, Cristian Ardiles, Guillermo González

Cluster analysis is used to design grade soft-sensors in a rougher flotation plant and a ball mill overload soft-sensor. Soft-sensors are virtual sensors which either replace unavailable actual sensors or infer measurements for non existing sensors. In the case of the grade soft-sensors clustering serves to determine clusters of related operating points. To each cluster there corresponds an ARMAX model structure whose parameters are estimated using only the points in the corresponding cluster. Thus a much better correlation is found than if all the data points were used for a global model. The problem of identifying clusters when the measurement of the real sensor is not available is addressed. In the case of the overload soft-sensor, variables were selected which are related to overload, either from a phenomenological point of view or according to operator experience. Different clusters are formed, some of which are identified as determining an overload condition or a possibility of such condition. Each of these clusters has a set of operating conditions which suggests the corrective action to be taken when necessary. Both kinds of soft-sensors are tested with industrial plant data and promising preliminary results are obtained.

Jan 1, 1995

By Roderick K. Davey

The objective is to develop a short-range mining plan which satisfies management and operating criteria and also "dovetails" with the long-range mining plan. In the past years, this objective was accomplished entirely by manual methods. Today, the computer is used to assist the engineer with this task. The results provided by these programs usually are incomplete and require further manual manipulation. The advantage of using the computer programs is that the program can be used to evaluate alternative plans on a first-cut basis minimizing the manual work. Subsequently, the most promising alternatives can be analyzed in more detail, commencing with the first-cut results. In this specific case history, one technique for using computer programs to assist with short-range mine planning will be discussed. Some of the basic operating and management criteria considered directly and indirectly are as follows: (1) operating criteria which include minimum and maximum shovel cut size, equipment performance, haulage roads, requirements for blending, and plant capacities; and (2) management criteria which consist of production requirements, cash flow requirements, return on investment, market demands, and availability of capital.

Jan 1, 1979

By C. L. Karr

Researchers at the U. S. Bureau of Mines have developed a technique for producing adaptive control systems using fuzzy logic and genetic algorithms. These controllers can be used to efficiently manipulate complex systems in real-time. Furthermore, they can achieve an acceptable level of control despite limited feedback in the problem environment. The control systems that result from the implementation of the Bureau-developed technique are able to recognize when changes have occurred in the problem environment, evaluate the magnitude of these changes, and alter the strategy being used to control the problem environment. Fuzzy logic is used to provide the controller with a rule-base that mimics the "rule-of-thumb" approach generally adopted by humans in the area of process control. Genetic algorithms are used to provide the controller with the adaptive capabilities necessary for the control of complex time-varying processes popular in the minerals processing industry. The effectiveness of this technique is demonstrated on a laboratory pH titration system. The pH system includes a changing setpoint, titrants with varying concentrations, and the possible addition of a buffering solution.

Jan 1, 1993

By Solomon S. Katz

As more and more computer software is written for geological mapping applications, the users of the software are discovering the problems of transferring data between the programs, maintaining correct data and integrating maps produced last week with those produced today. One way to deal with these situations is by using a geographic information system (GIs). Last September the USGS and National Academy of Science held a 5-day GIs symposium on integrating technology and geoscience applications (USGS, 1988). It was followed in October by GEOTECH '88 (Peters and Krajewski 1989) which had a session exclusively for GIs applications in the Geo-Sciences. Editorials in Geobyte (Leonard, 1986, 1988) suggested that geographic information systems will be the next major computer programs to be adopted by the mineral industries. As far- back is 1985, the Computer Oriented Geological Society (COGS) printed An Introduction to GIs in their newsletter (Katz, 1985). About 20 years ago, a revolutionary idea occurred in the world of business data processing. It was the idea that all related data be stored in a standard format, in a single place and that all related computer application programs would use the same data.

Jan 1, 1989

By Munson R. McKinney, Bryan A. Slim

To date some 1,000 exploration targets (by way of adits, mine dumps, shafts, outcrops and unstoped mine areas) have so far been identified using an interactive data base system to query a digital data base comprising topographic, cadastral geological and mine components developed as a compilation of old plans, records, surveys and recently flown aerial photography. The exploration targets are intended for early follow-up as part of a 1987 exploration programme to investigate the reserve potential of the former producing property located in southern Utah. Of further interest is the unscrambling of old mine plans to provide drill targets for investigation of unstoped reserves with one target being a possible 800,000 tons in part of the lower workings. The project site encompasses about 3,200 acres of mainly patented lode claims covering most of the claims and mines of the Gold Mountain mining district formed in 1889. Turn of the century mining saw several mines operating whose total production was at least 143,000 oz. gold and 460,000 oz. silver from steeply dipping veins up to 20 ft. or more in thickness.

Jan 1, 1987

By A. Pavlides

The purpose of this work is to conduct a preliminary analysis of the spatial variations of the thickness of lignite layers in the area of the Amyndeo mine, and to estimate the lignite reserves of the mine. The reserves are estimated by the method of the Voronoi diagrams, using a group of mirror points to close the polygons around the boundaries of the mine. Two data sets are investigated. The first one corresponds to an exhausted part of the mine. The derived reserves estimates are compared with the actual data obtained by the Public Power Corporation (PPC) to validate the analysis. The second data set extends over the entire mine, and it is used to derive an approximate estimate of the total lignite reserves. A geostatistical analysis of the total layer thickness is performed. The experimental semivariograms are evaluated for both data sets in different spatial directions. Two possible theoretical models for the experimental semivariogram (the exponential and a novel Spartan model) are compared and discussed. An interpolated kriging map of the total thickness variation is produced accompanied by a map of the kriging precision. The performance of kriging interpolation is discussed in terms of cross validation measures.

Jan 1, 2007

One of the major objectives of cost analysis is to enable the manager to predict the financial outcomes of decisions. To accomplish this, the future costs and benefits of alternative courses of action must be determined. If care- fully used, information about past financial performance can be helpful in this analysis despite the fact that, by definition, financial reporting information is historical. In many cases, both revenues and costs need to be estimated for decision- making. For the production manager, additional revenue is a result of increased throughput or recovery of valuable material from the stream of mined material. A reduction in operating cost, although similar to a revenue increase in its financial impact, is estimated using slightly different techniques. Generally, the estimation of cost is more difficult than the estimation of revenue. Most cost estimates have two components: an estimate of fixed costs and an estimate of variable costs. As discussed in chapter 5, the total cost of an activity during a specified period can be expressed as: Total cost = (Variable cost per unit of activity) x (Units of activity) + Fixed cost or TC = VX+F

Jan 1, 1999

By J. R. Stoltz, E. Thompson, S. Pattee

On May 15 and 16, 1999, a mine ventilation survey was performed in the 705-m- (2,312-ft-) deep Cayuga Mine, Cargill Salt Division, Lansing, NY. The purpose of the survey was to develop a numerical model of the existing ventilation system and to perform a computer simulation study for long-term environmental and ventilation planning. Because the natural ventilation pressure (NVP) has significant effects on the ventilation system at the Cayuga Mine, there was a need to assess the NVP acting in the mine. Due to the ventilation arrangements in the Cayuga Mine, the authors decided to use the direct-measuring method to determine the NVP by measuring differential pressure across the automatic fan door. This difference in pressure was measured immediately after the fan was stopped and the automatic door was closed to stop the flow throughout the entire mine. To show seasonal changes in NVP, two additional measurement for NVP were performed, one on Aug. 22, 1999, during the hot (summer) season, and another on Feb. 6, 2000, during the cold (winter) season. The mutual interaction between the natural ventilation pressure and the main fan at the Cayuga Mine is also discussed

Jan 1, 2003

By M. J. Virnig, C. P. J. Van Vuuren, A. J. Botha

The Zadra, AARL and organic elution processes and variations of them are presently widely used to recover gold from activated carbon. Despite this the study of the kinetics of elution have received relatively little attention. It is the aim of this study to investigate the rate processes taking place during elution in both inorganic and organic solutions. Batch adsorption and elution rate and equilibrium experiments were performed. The spatial concentration of gold inside carbon particles at various stages of the adsorption and elution processes were measured with a scanning electron microscope using an image analyzer to control and manage the micro-analysis data. The activated carbon particles exhibited film and intra-particle mass transfer rate- controlled behaviour during adsorption in a caustic aqueous solution at 95°C. Elutions in the aqueous caustic acetone solution at 30°C and the caustic aqueous solution at 95°C were unaffected by change in stirring rate. Elution was modelled by desorption reaction rate-control at the outer surface of the carbon particle. Adsorption and elution isotherms under duplicated solution conditions showed reasonable agreement for the inorganic solution and a large disparity for the organic solution.

Jan 1, 1993

By A. J. Hendron, B. Mohraz, R. B. Peck

INTRODUCTION The state of the art of soft-ground tunneling was discussed in detail by the senior author at the 7th International Conference on Soil Mechanics and Foundation Engineering held in Mexico City in 1969. Little can be gained by repeating the information assembled at that time. Hence, in this report, only the briefest summary will be given of the overall state of the art and attention will be concentrated on trends and developments since 1969. A characteristic of recent developments is the continued trend toward use of shields and excavating machines. The implications of this trend with respect to design and construction, and particularly with respect to the treatment of unfavorable ground conditions, will be examined. Settlement associated with lost ground, a subject as old as tunneling itself, will be reviewed and methods will be considered for its reduction. Design of tunnel supports was discussed in detail in 1969 with respect to essentially rigid or essentially flexible types of linings. In this report, a definition of flexibility will be considered and design procedures suggested for linings of flexibility intermediate between the two extremes.

Jan 1, 1997

By Salt Lake City Research Center, D. G. Foot, J. D. McKay

As part of its research program on column flotation, the Bureau of Mines, Salt Lake City Research Center has performed studies on (1) column flotation amenability and comparison with conventional flotation results for over 15 mineral systems, (2) alternative methods for improving column bubble generation systems, (3) mineral behavior within a column, and (4) the effect of changes in column operating parameters on flotation grade and recovery. Based on results from these studies, flotation columns (1) are capable of producing higher grade concentrates in fewer stages than conventional flotation cells at equivalent or increased recoveries, (2) require less retention time than conventional flotation cells, and (3) can be divided into cleaning and collection zones that have characteristic mineral-upgrading-per-foot values. Attempts to improve the column air sparger have led to the development of a superior external bubble generation system, which can (1) achieve increased air holdups. (2) produce bubbles from 400 Um to 4,000 Um average bubble diameter with minimal frother addition, (3) provide superior bubble size control, and (4) be maintained without column shutdown. Efforts are continuing to improve column flotation and transfer successful technology to industry.

Jan 1, 1988

By T. T. Chen, J. L. Jambor, J. E. Dutrizac

A reconnaissance study of the neutralization potential of 30 diverse minerals, 28 of which are silicates and aluminosilicates, has shown that most of these minerals contribute minimally to the neutralization potential (NP) in standard static tests. Feldspars in particular give low NP values and would not be expected to attenuate the acidity to any significant extent in acid rock drainage settings. The BET-determined surface areas of the minerals vary considerably, and the large surface areas of some of the pulverized samples have clearly affected the NP values even though the standard static-test protocol was used for the preparation of the samples. The low NP values of most silicates and aluminosilicates are in general agreement with the laboratory-determined slow dissolution rates for these minerals. The results suggest that, in the prediction of whether rocks will be acid-producing, the most realistic measure is that of the carbonate content. In mine wastes from metalliferous ore deposits, the contribution to the NP by the non-carbonate gangue assemblage is unlikely to be more than a token amount until well after the establishment of an acid rock drainage situation.

Jan 1, 2000

By William D. Hanson

Celestine (celestite) (SrSO4), the primary ore mineral of strontium, is present in the DeQueen Limestone Member of the Trinity Group (Lower Cretaceous) in Sevier, Howard, and Pike Counties, southwest Arkansas. Two mappable celestine beds have been identified. One bed is commonly 3-5 in. thick, but ranges up to 18 in. in thickness; the other bed is generally 2-3 in. thick. The beds are concordant within the DeQueen Limestone and were formed by precipitation from periodically restricted sea water. Reports concerning celestine date back to 1929, when Hugh D. Miser and A. H. Purdue mapped the geology of the DeQueen and Caddo Gap quadrangles. A small amount of celestine was produced in the early 1940s in Howard County. During 1941, the J. W. Hintze Company collected 1,500 pounds of celestine for testing purposes. In 1942 and 1943,750 test holes were drilled by the Bennett-Clark Company in Howard County. Afterward, approximately 90 tons of celestine was open-pit mined and shipped to Texas for processing. Since then, no mining of celestine in Arkansas has taken place.

Jan 1, 1999

By Mario Eduardo Rossi

The Universal Kriging (UK) and the Ordinary Kriging (OK) systems of equations are variations of the well-known system of Normal Equations. They differ only by the number of constraints present in the system. The dual version of these sytems enables one to interpret kriging as the fitting, of an interpolation surface, whose components are a series of variogram functions plus a polynomial trend model. This trend model should account for any systematic decrease or increase of the variable over the study area. It is shown that modeling the trend is useful only when the locations being estimated are beyond the range of influence of neighboring data (extrapolation cases). A case study based on a public-domain coal data set is presented. The variable described (seam thickness) shows an actual trend of increasing data values towards the NW corner of the region considered. UK and OK are used to estimate coal thickness at locations within sample data range (interpolation cases). The UK algorithm that includes a model for the trend does not improve the estimation when compared to the simpler OK algorithm with no trend model. Thus, in interpolation situations, the simpler OK algorithm is recommended.

Jan 1, 1989

By S. Mathur

Oxide particles are commonly used as fillers in plastics, paper, rubber, etc. (particulate composites). The successful fabrication of such composites is dependent upon the adhesive strength of the filler particles to the matrix. The compatibility of the matrix and the filler particles is generally enhanced by the adsorption of surface modifiers such as surfactants and polymers at the particle-matrix interface. To develop a scientific basis for the selection of the appropriate modifiers it is necessary to understand their adsorption mechanisms. specifically, the adsorption of polymeric additives is attributed to a combination of chemical and electrostatic interactions, hydrogen bonding and van der Waals forces. Hydrogen bonding has been suggested to be the primary adsorption mechanism for nonionic polymers. However, a literature survey of the Poly(ethylene oxide) (PEO)-oxide system suggested that PEO, a nonionic polymer, was substrate specific. A systematic study was undertaken to investigate the adsorption mechanisms of PEO on oxide particles. It was determined that strong Bronsted acid sites on the surface interact with the ether oxygen, a Lewis base, of PEO to induce adsorption. In this work, characterization of PEO binding sites on oxides is reported and the mechanisms of PEO adsorption are discussed.

Jan 1, 1999

By L. M. Chan, D. H. Carlson, J. H. Johnson

This paper discusses laboratory evaluation of a tailpipe emissions measurement apparatus (EMA) developed by Michigan Technological University (MTU) under contract to the Bureau of Mines. The apparatus dilutes diesel exhaust and measures the concentrations of diesel particulate matter (DPM), CO, C02, NO and NO2 at known dilution ratios. The EMA was evaluated by side-by-side comparison of its measurements with those by laboratory grade instruments. During the preliminary laboratory evaluation concentrations of DPM, CO and CO2 were measured. The concentrations of CO and CO2 measured by the EMA were usually within ±14 pct of laboratory-measured values for CO and ±20 pct for CO2. EMA DPM concentrations correlated well (r = 0.96) with the laboratory values, but were 29 pct lower on average. The CO and C02 differences were observed to be related to the method of calculating the EMAs' dilution ratio and the difference in DPM concentrations is attributed to thermophoretic and/or condensation losses related to the EMA's unheated sample probe. Preliminery analysis of data obtained with a heated sampling probe and modifications in the sampling procedures have indicated reduced variability in DPM and in the calculated dilution ratios.

Jan 1, 1991

By J. T. Sitarski, R. C. Emmett, L. W. Luinstra, R. P. Klepper

A mining operation in Zimbabwe produces a pyritic gold concentrate that requires oxidative pretreatment prior to cyanidation in order to liberate 80 percent of the gold values. Bio- oxidation offered the potential of increased gold recovery and was considered to be an economically advantageous alternative to the existing practice of roasting the concentrate. Based on bench- scale test work, a small bio-oxidation plant, capable of processing approximately 50 percent of the concentrator production, was installed at the mine to evaluate this approach. The plant included two 57 m3 bioreactors in series and the ancillary equipment needed to prepare the feed concentrate, to wash the leached residue prior to cyanidation, and to neutralize the waste liquor. The plant was operated for a year-and-a-half, and the conditions needed to achieve a 90 percent liberation of gold values were determined. A number of critical technical problems were encountered, and many were resolved on-site. Others have been addressed since the pilot plant was moth-balled in June 1988. Valuable insight was gained from the operation of the pilot plant, which has provided useful guidance for continued process and equipment improvement.

Jan 1, 1990

By T. M. Barton

This paper presents several case studies in which a mechanics-based boundary-element program is used to back-calculate the surface subsidence associated with various panels at several northern Appalachian coal mines. The program used in this case study is called LAMODEL, which incorporates a frictionless, laminated overburden into a general-purpose displacement-discontinuity code primarily designed for calculating the stresses and displacements in coal mines or other thin-seam or vein-type deposits. In this paper, the program is used to calculate both the underground convergence and the resulting surface subsidence at five longwall panels and a room-and-pillar section. The fitted subsidence from the model is compared with the field measurements and analyzed. The results from this work show that the LAMODEL program is not as accurate as available empirical subsidence-predictive methods; the expected correlation between the geology and the optimum input parameters is not evident. However, for a mechanics-based program, LAMODEL does provide moderately accurate subsidence calculations, and it is one of a few programs that can even attempt to practically calculate both underground stress and convergence and the resulting surface subsidence.

Jan 1, 2000