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By J. Hanna, H. R. Gonzalez

Four Ca-bentonitic clays from Alabama were evaluated for use in diammonium phosphate (DAP) or urea ammonium nitrate (UAN) fertilizer suspensions. The viscosity and gel strength of suspensions prepared with different proportions of a Western bentonite clay and sodium-exchanged Alabama clays were measured as a function of clay content and dispersant concentration. The results obtained suggested that three of the Alabama Ca-bentonites would replace about 40% of the more expensive Western bentonite in UAN and DAP fertilizer suspensions. The performance of the Nu-modified clays, prepared according to the Tennessee Valley Authority soda ash method, was as good or even better than those observed for the Mg-, NaIMg- or K-modified clays. The TVA clay modification procedure appears to be reliable and cost effective.

Jan 1, 1991

By Richard S. Mateer

The percent ash in a coal blend is equal to the weighted average of the ash contents of the component coals. If the raw coals differ in washability characteristics, the total yield may be maximized by washing the component coals to different quality levels. A mathematical basis for blend maximization is developed and a computer program is described The program determines the component weights that maximize the yield, while meeting an individual coal-quality specification. The procedure is directly applicable to linear parameters of grade quality such as percent ash, percent sulfur and the calorific value. A transformation of variables permits program execution to meet a sulfur-compliance specification. Blends may consist of any number of component coals.

Jan 1, 1997

By Shahzad Moosa, John M. Pitt

Statistical variability in rock strength can be evaluated by rapid, inexpensive ultrasonic pulse velocity measurements, an important consideration since rational probabilistic design in rock is often hampered by the cost of obtaining sufficient strength data. Experimental ultrasonic pulse velocity measurements on a set of 96 limestone specimens showed two distinct statistical populations. Both populations followed Weibull distributions, with flexural strength distributions paralleling pulse velocity distributions. Thus, experimental results suggest that strength variability may be predicted from a few rationally selected strength measurements and several ultrasonic tests. The correspondence between strength and velocity may then be used to develop an experimental transformation function, allowing the development of a statistical distribution function for strength based on the known statistics of velocity. Comparison of experimental groups with full sets of corresponding strength1 velocity data showed the technique offers a fairly accurate description of the statistics of strength.

Jan 1, 1986

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 C. Garcia, H. Arias, J. D. Miller, C. L. Lin

The question of ultimate recovery in heap leaching operations is always of particular concern with respect to economic considerations. Of course the particle size distribution is a critical factor which determines ultimate recovery and which must be established based on a balance between the extent of mineral exposure and transport phenomena. Now it seems that the ultimate recovery for a given particle size distribution can be established from mineral exposure analysis by x-ray microtomography (XMT). Using recently developed software, micro-CT data can be used to determine the fraction of mineral exposed and thus the ultimate recovery. Examples of mineral exposure analysis are given for the copper heap leaching operation at Zaldivar, Chile.

Jan 1, 2002

By C. DeRossett, K. F. Unrug

Sedimentary rock fractures commonly occur in the vicinity of outcrops. Mine highwalls and highway cuts provide excellent views of these near-surface joint systems. This paper explains the origin, characterization, distribution and extent of the these joint systems with reference to the lithologic composition of the rocks. The practical implications of these joint systems on the operation of a mine are described. Included are discussions of the discontinuous deformation that results from surface subsidence, the stability of mine portals and near-outcrop underground operations, and the stability of highwalls when using highwall miners and strip operations. Some design procedures are recommended to minimize the problems encountered within mining areas having intense joint systems.

Jan 1, 1996

By H. Y. Sohn, H. K. Lin

The leaching of primary porphyry chalcopyrite ore under simulated solution-mining conditions was studied using a packed-bed reactor. A mathematical model incorporating the intrinsic leaching kinetics of chalcopyrite and pyrite grains, the pore diffusion of dissolved oxygen within the ore fragments, liquid-solid mass transfer, and the effect of fluid flow and axial dispersion was formulated and tested for the overall leaching process. The dependence of oxygen solubility on ionic strength of the solution was also incorporated into the model. Satisfactory agreement between model pre- dictions and experimental data was obtained. The model can also predict the rate of the leaching process under different temperatures, oxygen pressures, solution flow rates, and different size distributions of ores.

Jan 1, 1991

By S. S. Hsieh

As part of a program to address the long-term need to ensure adequate supplies of domestic phosphate raw materials, the Tennessee Valley Authority (TVA) has conducted considerable research on dolomitic phosphate rock beneficiation. The discovery that alkyl diphosphonic acids act as phosphate mineral depressants led to the development of several processes involving a carbonate flotation step for the effective beneficiation of these problem ores. Most recently, a partial deoiling process in which the reagent consumption is greatly reduced has been developed. The reduction is achieved because part of the initial feed is beneficiated without passing through the separate carbonate flotation step. Using this method, a phosphate product containing 30.6-30.9% P2O5 and 0.7-0.8% MgO was obtained from a Florida dolomitic phosphate pebble that contained about 23% P2O5 and 2.0% MgO. The P205 recovery was 80.8-86.5%.

Jan 1, 1991

By M. J. Gula, S. S. Xue, E. P. Horwitz, J. T. Harvey

A study was conducted to control iron in copper electrolyte streams using Eichrom Industries' new monophosphonic/sulphonic acid resin. The resin strongly and selectively extracts ferric ion over copper and cobalt from highly acidic copper electrolytes. The resin has a loading capacity of 27-g/L iron and can be readily regenerated. In addition, the new resin can easily be synthesized using commercially available starting materials. This paper presents the experimental results for iron control in copper electrolyte streams using the new resin and discusses its potential applications to other hydrometallurgical streams.

Jan 1, 2002

By B. Huang, H. Sevim, R. Honaker

The use of medium-to-high sulfur coals has been negatively impacted by the 1990 Clean Air Act Amendment (CAAA). In this article, a method is demonstrated that can render these coals competitive and yet compliant with Phase II of CAAA. The method uses strategic mining and optimized preparation plant operation to minimize production costs, and it utilizes advanced coal-cleaning technology and an SO2 allowance to produce a compliant coal. The method is illustrated through an example from southern Illinois. For an annual production of 3.2 Mt (3.5 million st) and with a $150/st SO2 allowance cost, it was possible to produce a competitive coal for $0.84/million Btu. The production and allowance costs were $0.608/million Btu and $0.232/million Btu, respectively.

Jan 1, 2002

By Kal V. S. Sastry, Stephen N. Little

Computer simulation of comminution systems is found to provide significant cost savings by enabling efficient circuit design and development of control systems. These simulation systems are based on sound mathematical models and numerical methods. Nevertheless, they are found to be hard-to-use and hard-to-modify to carry out more elaborate process analysis. This paper discusses the fundamental principles and practical aspects of an advanced, highly functional, and user-friendly SIMulator for COMminution, SIMCOM, that is being developed at Berkeley by incorporating state-of-the-art software engineering principles.

Jan 1, 1992

By Scott K. Palm

The initial intent of the Hazard Communication Standard (HCS) was to improve worker health by providing more information about the hazards of chemicals used in the workplace. However, the impact of the HCS goes well beyond worker right-to-know. There are direct costs associated with compliance. In addition, labelling and hazard communications can provide a competitive advantage to producers of minerals that have not been identified as hazardous. Often, the lack of hazardous information about a substance is due to the lack of scientific study, rather than an indication of product safety. Currently, industry and regulators sometimes give known hazards greater weight than unknown risks.

Jan 1, 1991

By Stanislaw Wasolewski

Computerized systems for ventilation parameters monitoring which are used in Polish coal mines provide the ventilation staff with a great number of measuring data. These data can be used to get knowledge about dynamic properties of ventilation process and disturbances affecting its state. This is necessary to create a reasonable concept of mine ventilation control system and make a practical application of such system. In the paper a method of ventilation process identification with the use of measuring data from monitoring system is described. Computer analysis of time series including statistical, correlation and frequency methods are applied to estimate dynamic properties of ventilation process and its disturbances. Using the Fast Fourier Transformation (FFT) algorithm the parameters of the process have been obtained which can be efectively used in a system for mine ventilation control.

Jan 1, 1991

By John L. Watson, Suren Mishra

Many of the wastes produced by modern steel plants are pulps or sludges containing significant concentrations of iron and displaying some ferromagnetic characteristics. These waste materials are often suited to treatment by magnetic cycloning to produce a high solids content underflow and a clean water overflow. Alternatively in the classification mode, the magnetic cyclone can produce a high iron underflow product for recycling by discarding fine non-magnetic material to the overflow. Results for the treatment of a variety of steel plant wastes in 5.0cm, 2.5cm and 1.25cm diameter cyclones, operating with and without an applied magnetic field, are presented. It is demonstrated that the magnetic cyclone increases solids recovery to the underflow product, especially at finer particle sizes and for higher solids content feed pulps.

Jan 1, 1992

By A. K. Ghose, S. Chakraborti

The research work outlined in this paper examines the utility of index tests for evaluating the strength of coal, both in the laboratory and in-situ. For routine evaluation of strength and deformation properties of coal seams, as inputs for design in stability analysis and equipment selection, the index tests are cost-effective and also make less demand on time and manpower. Four index tests, namely Protodyakonov Index, Cone Indenter Index, the Point Load Strength Index and Schmidt Rebound Hammer, were evaluated for 13 coal samples and correlated to fundamental strength and deformation properties such as uniaxial compressive strength, Brazilian tensile strength and modulus of elasticity of the same coal stratum. The index tests, barring Point Load Index, showed relatively low percentage scatter compared to the fundamental strength and show marked advantages for routine estimation of coal seam strength.

Jan 1, 1986

By L. P. Meade

The need to feed an established talc mill from a crude ore source located closer to the mill prompted the 1986 drilling of a previously mapped, talc-carbonate deposit. This talc-bearing rock had never been considered a potential source of crude talc ore because of the high carbonate content and other deleterious minerals observed in outcrops. Selective mining, in-pit grade control and creative processing have allowed this deposit to be developed into an ore body. By definition, an ore body has to be a source of positive cash flow. With industrial minerals, this is determined as much by market acceptance as by ore tenor.

Jan 1, 1994

By Brian H. Kaye

Efficient design of grinding circuits for efficient production of ultrafine material requires rapid feedback of information concerning the fineness of material leaving the grinding device Generating this information requires efficient sampling and adequate rapid characterization of the material leaving the grinding machinery Recent developments in electrooptic inspection of dry and wet material leaving a grinding device are critically reviewed New methods for characterizing ultrafines are discussed A rapid operating automated cybernetic (intelligent) permeability device for automatic control of grinding circuits using Blaine Index and other fineness indices is described

Jan 1, 1983

By N. P. Reddy, Y. J. Wang

Stall or aerodynamic stall of axial flow fans has long been recognized as an important operational problem in mine ventilation. To develop a technique for characterizing fan stall in multiple fan ventilation networks, a research project was initiated through the Generic Mineral Technology Center for Mine Systems Design and Ground Control. Considering that fan stall is related to multiple operating points, this paper discusses a numerical model for multiple fan ventilation networks, and numerical methods for solving multiple networks solutions. It is hoped that the results of this project will lead to an innovative method of ventilation network analysis and simulation, thus preventing stall.

Jan 1, 1993

By Ken Takahashi, Yuuich Umeki, Masahiko Arakawa, Dr. Tominaga. Yuusaku

Macroscopic characteristics of a complicated mine ventilation is remarked to build an expert system for mine safety in the Taiheiyo coal mine, Hokkaido, Japan. To gain the characteristics a large number of simulation were performed with varying aerodynamic resistance of the branches with regulator in mine ventilation network. The principal results of the study are as follows, (1) Pressure loss diagram for ventilation network with main and auxiliary fans enables capability of air circulation in the network. (2) H-Q (pressure-quantity) diagram gives capacity of air quantity In a network with main and auxiliary fans. (3) When airflow rate, [] through branch qi is changed by opening/closing regulator set in the branch, air flow rate, [], through branch p can be represented by the empirical formula. [ ] where Api and Qp,o are the constant coefficients. (4) Macroscopic characteristics mentioned above are available to make rules in an expert system for escaping route at emergency.

Jan 1, 1989

By K. G. Sutterer

The prevalent use of coal combustion byproducts in engineering applications has been with Class C and Class F fly ash as admixtures in structural concrete. But, the use of fly ash and bottom ash byproducts from modern desulfurization processes is receiving increased attention. The University of Kentucky has been conducting research into civil- and mining-engineering applications of these products. The studies have included extensive investigation of the geomechanical behavior of the materials and the effect of mineralogy on this behavior. These studies indicate important mineralogical considerations in the selection of materials for a specific application and highlight the importance of quality control before and during usage on specific projects.

Jan 1, 1997