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By Kenneth N. Han, Yichang Guan

The dissolution behavior of metals from Au/Ag/Cu-alloys has been studied using rotating disc electrodes in solutions containing acids, cyanide, and ammonia. Electrochemical methods as well as leaching tests were adopted in this study. The results showed that there was no galvanic effect on the dissolution of metals from homogeneous alloys. In aerated cyanide solutions, the dissolution of gold, silver, and copper from their alloys was partly controlled by surface chemical reaction, but largely by mass transfer. On the other hand, the galvanic coupling effect played a very important role in heterogeneous alloy systems.

Jan 1, 1995

By Felicia F. Peng, Victor Z. Sun, Syd S. Peng

A probability-based analysis method in conjunction with the finite element structure modeling technique to evaluate an entry system stability is developed. Variability of the rock properties and loading surrounding the entry system is taken into consideration to predict a roof stability by using the probability of failure instead of the common safety factor concept. A dynamic programming is applied to establish a recurrence relationship between the degree of potential roof fall and accumulated roof fall index in an area of interested. A probable distribution of roof fall is assessed by using a developed computer program, RFSTAB. The assessment of the roof falling boundary in the longwall entry system is used as the example to illustrate the procedure and effectiveness of this analysis method

Jan 1, 1996

By W. J. Fotheringham

This paper deals with the mining techniques employed at Canada Tungsten's northern Canadian operations, particularly with respect to their effect on productivity, safety, and stability of relatively large underground openings. The ore body was originally mined commencing in 1974 using conventional pneumatic jumbos in a topslice and horizontal benching room and pillar layout. Pillar stability became an increasing problem as mining progressed, leading to a re-examination and ultimately a conversion of mining method. Rock mechanics considerations and the effect of extraction rate on ground control costs and conditions are analyzed. Other areas discussed concern the results acheived through the use of large diameter I.T.H. drills, radio remote controlled L.H.D. units, and a unique system of hydraulic backfill placement.

Jan 1, 1985

By Guoming Liu, Weibai Hu

The designing aspects of column profile, cross-section and height, types of aerator or air sparger, and feeding and discharging devices have been designed and tested. In operating aspects, the flotation column: has beer, compared with the conventional mechanical flotation machine in large- scale plant practice. It has been found that the reagent conditioning time and the slurry residence time required in the column are longer than those in the mechanical flotation machine. The general opinion is that the flotation column can show some effectiveness in specific cases as long as it is properly designed and carefully controlled.

Jan 1, 1988

By P. J. Kientzler, Y. C. Lo

The current study is concerned with the analysis and attempt at simulating the product size distributions obtained from a vibrating ultrasonic device. Systematic experiments of comminution were performed with natural sizes as well as monosizes in order to understand the breakage behavior of the device. A precise analysis of the device's breakage performance in the case of fine grinding of alumina samples will be presented. Initial steps to model the breakage events using a detailed mathematical algorithm will be discussed.

Jan 1, 1992

By C. K. Nworu, L. O. Asuquo, C. O. Nebo

Selective flocculation studies of Agbaja iron ore with starch-type and nonionic polyacrylamide-type flocculants has been conducted to determine the effect of flocculant type. The results indicate that corn starch was slightly better than cassava starch in selectivity performance. Cassava starch was in turn better than Superfloc 16, while the poorest results were obtained with commercial starch. Sodium humate shows better dispersive capability, and thus enhanced flocculation results, than sodium silicate. Pulp pH affects the zeta potential, polymer chain configuration and hence selective flocculation. Overall results indicate that recovery and separation of this very fine grained iron oxide by selective flocculation is feasible.

Jan 1, 1995

By N. L. Anderson, R. Ramananantoandro, F. Wirnkar

Six-fold, high-resolution, compressional-wave seismic data were acquired across a coal mining property in the Meigs County study area, southeastern Ohio, with a view to differentiating the Clarion Coal Member and a truncating channel sandstone prior to longwall mining without costly drilling. The seismic technique, as is illustrated by our example data, was successfully used to map those areas where the coal is present, as well as those places where it was eroded by incising fluvial streams. Our results demonstrate that the seismic reflection method, using an engineering seismograph, can be a cost-effective way to define discontinuities associated with coal seams.

Jan 1, 1992

By William M. Hartzler

The Powder River Basin (PRB) refers to the coal deposits located in southeastern Montana and the northeastern Wyoming counties of Campbell, Converse, Hot Springs and Sheridian (Wyoming PRB). In 1993, there were 20 active surface mines with 3109 employees in the Wyoming PRB (Annual Report, The State Inspector Of Mines Of Wyoming, 1993). Early PRB production growth was primarily in response to the passage of the Clean Air Act of 1970. The disproportionate growth in Wyoming as compared to Montana can be attributed to the differing coal taxation policies of the two states. The state severance and production taxes were significantly lower in Wyoming. However, Montana passed legislation in 1987 reducing the severance tax rate, substantially narrowing the severance tax gap. Campbell and Converse counties in Wyoming have benefited the most from the production growth in the region. Cyprus Amax's Belle Ayr Mine, south of Gillette, in Campbell County, was the first modern commercial coal mine to be developed.

Jan 1, 1994

By Donald L. Meredith, Jeffrey Harris, Donald A. Stanley

Principal Components Analysis (PCA) is a versatile, multivariate statistical method that the Bureau of Mines is applying to mineral processing data to achieve data simplification and pattern recognition. The principal components are obtained from an eigenanalysis of the data matrix. To achieve data simplification PCA replaces a larger number of measured variables with a smaller set of principal components and at the same time removes a significant amount of experimental error. Data simplification and error reduction make PCA useful in process control. Plots of the individual principal components form the basis of a pattern recognition technique that allows detection of significant variations in the structure of the data. These applications of PCA are illustrated with appropriate mineral processing data.

Jan 1, 1993

By Arthur W. Darby

Heathrow Airport is owned and operated by BAA who are engaged in a major programme of expansion. In order to link the expansion of the airport in the west with the existing central terminal area, a twin bore, 8.8m outside diameter, road tunnel,1280m long, is being constructed. The tunnel drives pass over, with limited clearances, an operating railway tunnel, and pass under, with about one diameter cover, the airport taxiways and aircraft stands. Selection of the machine was heavily influenced by the need to minimise settlement.

Jan 1, 2003

By Olice C. Carter, B. J. Scheiner

The Bureau of Mines investigated the removal of two toxic/heavy metals (cadmium (Cd) and lead (Pb)) from brass foundry wastewater. Polymers, copolymers, guars, and gums were used in conjunction with calcium hydroxide (Ca(OH)2) and magnesium oxide (MgO) to remove the metals from solution. Several polymers were successful in removing Cd and Pb from the wastewater. The concentrations of Cd and Pb were lowered from 19 to 0.01 ppm and from 20 to less than 0.01 ppm, respectively. The methods investigated could easily be adapted to many existing wastewater treatment facilities and/or be used independently.

Jan 1, 1991

By Kadri Dagdelen

The definition and shortcomings of traditional cutoff grades are discussed. . The concept of optimum cutoff grade policy which maximizes the Net Present Value (NPV) of annual cash flows coming from a mining project is introduced within the basic framework outlined by K. F. Lane. Several examples are used to demonstrate the shortfalls of cutoff grade policies obtained by various heuristic optimization techniques. An algorithm to obtain an optimum cutoff grade policy which maximizes the NPV of a project is given and described in detail.

Jan 1, 1992

By R. W. Hughes, R. Koopmans

This paper investigates the effect of varying stress levels on the determination of deformation moduli and examines the sensitivity of the borehole dilatometer in measuring rock mass scale features and its ability to represent rock mass characteristics. Cubical blocks of sandstone, limestone and granite were tested in the laboratory under triaxial stress conditions. Field programs were conducted in both granite and sandstone rock masses surrounding underground openings. The dilatometer's zone of influence was determined by conducting tests within an instrumented concrete cylinder and by performing a finite element analysis. Laboratory and field results suggest that the deformation modulus of a rock mass can be substantially affected by the stress field and that the borehole dilatometer is sensitive enough to profile deformation moduli as dictated by the in situ rock mass characteristics.

Jan 1, 1986

By G. Atesok, M. Hancer, M. S. Celik, O. F. Emrullahoglu

Multivalent ions are shown to activate the flotation of colemanite in the presence of sodium dodecylsulfate (NaDDS). Floatation recoveries versus barium ion concentrations exhibit three distinct regions of floatability. Adsorption, zeta potential and solubility mesurements under comparable conditions reveal that Region I is characterized by the uptake of Me2+ ions followed by electrostatic attraction of sulfate ions onto the oppositely charged surface. The improvement observed in flotation recoveries in Regions II and III is ascribed to surface and bulk precipitation of metal dodecyl sulfate onto colemanite, respectively. While the most soluble BaDDS ions yield the highest activation, the least soluble MgDDS achieve the lowest activation. It is postulated that metal ions depending on their solubility products with DDS are capable of activating the boron minerals.

Jan 1, 1993

By Andrew J. Neale, Mark Franklin, Mike Cooper

Although recent advances have significantly improved our understanding of flotation fundamentals, disturbance variables combine to make it difficult to maintain steady state operating conditions over either the short or long term. One of the major concerns relates to knowing how much reagent to add to the flotation system, how to monitor the addition rate, and how to determine when to adjust the reagent addition rate in the presence of these disturbances. This paper will look at the development and installation of process control systems that address these issues. The economic benefits that accrued from the implementation of these strategies is described.

Jan 1, 1994

By P. Brumit, L. Grady, R. Mitts, V. Holm

The Mesquite mine is a large, open pit, heap leach gold mine owned and operated by Gold Fields Operating Co.-Mesquite. The mine uses a fully integrated mine planning and reserve modeling software system developed at the mine. This system has recently been extended to include short-term mine planning, grade control, and daily production reporting. The grade control portion of the program uses a multiple indicator kriging (MIK) approach using the blast-hole spacing and exploration assays. The program permits ore control geologists and mine planning engineers to have immediate access to all the information.

Jan 1, 1991

By Hassan El-Shall, Abbas A. Zaman, Brij M. Moudgil

The addition of organic and inorganic dispersants to aqueous suspensions of heterogeneous particles (kaolin) was found to significantly affect the solubility of metal ions from kaolin particles and stability of the dispersion. In most of the industrial applications of kaolin, highly concentrated slurries of controlled stability and fluidity are required. The solubility of kaolin particles in terms of aluminum and silicon ions and its effect on the stability of the slurry was investigated. The main objectives of this study were (1) to study the effect of the extracted metals on the properties and performance of the slurry, (2) to understand the reaction mechanism of dissolution of metals from kaolin, and (3) to understand the interaction mechanism of dispersants with kaolin particles. The controlling variables were dispersant dosage, slurry pH, solids loading, and aging.

Jan 1, 2003

By A. J. Monhemius, R. G. Reddy, G. W. Warren, E. Peters

Thermodynamic solubility of chromium in pickling solutions (i.e., HF- HN03-H2O solutions) was determined as a function of HF and HNO3 acid concentrations at 298K. Pure Cr, AISI type 316 and 416 stainless steel were used in this study. The results showed that the solubility of Cr increased with increase in the concentrations of HF and HNO3 acids in solutions. The solubility of Cr increased in the order of pure Cr > 416 SS > 316 SS. The theoretically calculated Cr solubility data were in reasonable agreement with the experimental data.

Jan 1, 1993

By D. Lenartowicz, K. R. Alexander, M Collings

Cosmo Howley is a gold deposit in the Northern Territory of Australia. The geology is complex and the input of geological data is an important part of the grade control process. As the geology of the deposit has become better understood, grade control and mining techniques have evolved to meet the changing circumstances. Present grade control depends on the use of angled blast holes, 21/2 benches and selective mining. Data is processed on site using 2 386 PC's running Surpac software. An environmental protection programme is employed, including soil stripping and stockpiling, sulphide waste containment and water quality monitoring.

Jan 1, 1989

By Steve Kral

The success of the industrial minerals end of the mining industry is often overshadowed by the high price of copper, the glamour of gold, and the nation's huge reserves of coal. Those three segments of the industry, however, along with every other business in the world, could not function without the products that are composed of a variety of industrial minerals. And, according to Haydn H. Murray, past president of SME, the value of industrial minerals in the United States is more than triple that of metals, about $19 billion a year versus $6 billion. In the developed countries of the world, he said, the value of industrial minerals is nearly always greater than the value of metallic minerals. Murray, also a professor of geology at Indiana University, was the luncheon speaker at the SME-sponsored Grinding of Industrial Minerals conference held in Asheville, NC this past September. Producers of industrial minerals know they must squeeze the maximum value out of the industrial mineral being mined and processed, Murray told the audience of about 100 people. Grinding and particle size, then, are vital to a commodity's profitability.

Jan 1, 1990