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By Z. Abdel-Khalek, Hassan El-Shall, S. Farrah, C. Boice

Selective adsorption and surface modification of minerals by surfactants is the primary step in the process of separating certain minerals with similar physical and chemical characteristics in the flotation process. In this study, microorgan- isms are used as surface modifiers for francolite and dolomite. Results of adsorption experiments with francolite and dolomite show that the microbes selectively adsorb to one of the minerals under specific operating conditions. In preliminary flotation experiments, it is found that the microorganisms enhance or depress flotation of the minerals leading to an increase in the efficiency of separation between the francolite and dolomite. The conditions leading to selective adsorption (surface modification) and subsequently to possible efficient separation of these two minerals are discussed in this paper.

Jan 1, 2002

By M. Josick Comarmond, John J. Jeffery, John W. Bennett

Oxidation rates of sulfidic mine wastes measured at a range of size scales have been collected from a number of sources. The results suggest that well-designed laboratory columns, under controlled conditions, provide comparable information on oxidation rates to that obtained from field test piles. It has been found in the cases presented that laboratory measurements of oxidation rates of a particular material type can be applied with confidence to the same materials in the field. It is recommended that a further study be undertaken to measure the time-dependence of the oxidation rate for a range of particle sizes and different materials. This study would provide measurements against which models of oxidation rate as a function of time and particle size can be tested, to give confidence in the use of models to describe dump behaviour in the longer term.

Jan 1, 2000

By Christian Jeger

After recalling the principles underlying fire-damp flow in coal and the essential part played by permeability (Darcy's law) in the intensity of flow, a few theoretical and experimental results showing the possible causes and range of variation of coal seam permeability are presented. The study of firedamp flow into gate roads and of residual gas concentrations in coals as a function of the gate road distance, shows that, in French mines, coal seams in a virgin zone have a very low permeability, but they become permeable when destressed by mine workings, in particular overlying workings. This is the case not only in the fractured zone round a mine excavation in which the gas is released, but also beyond the limit of the zone degassed by the excavation. In the floor of flat seams, upward boreholes can be used for predegassing seams that have been relaxed but not degassed, as the result of an overlying coal face. In this respect we shall describe the predrainage experiment carried out in the Marienau district of the Lorraine coalfield. Predrainage can contribute considerably to the reduction of methane emission in the ventilation of newly opened longwall faces. But to be efficient and useful predrainage should meet certain conditions.

Jan 1, 1980

By Lynn B. Hales, Randy A. Ynchausti, Robert W. Colby

Process control systems have evolved from single loop control to distributed control with computer based expert control strategies. The next step is to add adaptive control to the expert control strategies. An object-oriented intelligent adaptive optimization approach is defined and simulated results are presented.

Jan 1, 1995

By J. B. Griffiths

Clearly there is a tremendous need for assistance in Eastern Europe since most industries must undergo major restructuring. The new governments face many dilemmas, the first task being to establish an order of priorities to deal with the numerous problems at hand. Issues such as the standard of living take low priority compared with market economy and ecological problems. The concept of a Comecon market is now virtually non-existent and trade in roubles ceased from 1991. From this time onwards countries were obliged to trade using free market prices. Governments must also avoid the economic mistakes of countries such as Poland with its high devaluation and lack of economic control and, if possible, contain inflation and unemployment. The privatization of Eastern European enterprises raises considerable difficulties, particularly for large corporations, employing anywhere from 50-100,000 people, which played a major role in the national economy. Whichever method is selected, however, still has to overcome the problem of lack of capital and evaluating the national property. For example, earnings represent only a small percentage of the value of these national industries and thus cannot convert to private ownership without foreign capital investment, either direct or as joint venture capital.

Jan 1, 1992

By Giin-Fa Fuh, Sally A. Shoop

An instrumentation program was developed based on the results of an analytical study of the geomechanical effects of longer longwall face lengths. Boundary element simulations showed that longer face lengths can cause in- creased face convergence and an increase in the shear stresses in the immediate roof. Empirical design methods predict that longer faces will cause little effect on abutment stresses as long as the roof caving is well behaved. On this basis, a longwall face instrumentation program was designed with emphasis on the interaction between face support and ground response for optimizing face conditions. At a 600-foot (183 m) face, five midface shields and two headgate shields were monitored with vary- ing hydraulic pump pressure. The instrumentation included six convergence rods with linear potentiometers to measure canopy-to-toe convergence; fourteen pressure transducers to monitor leg pressures; and two portable data loggers. Similar instrumentation will be in- stalled on a 750-foot (229 m) face for comparison. The results from the 600-foot (183 m) face indicate that a ground reaction curve, as determined from the relationship between the sup- port set pressure and the roof convergence, can be used to optimize the support pressure to control convergence, the key element to ground stability in the face area.

Jan 1, 1986

By David D. Gallagher, Edmond J. O’Donovan

It has been well accepted for many decades that hard starting of conveyors has associated problems. It is particularity damaging to the belt and splices. Recent measurements of hard starts on a long conveyor with a low modulus belt showed very unusual responses. These included violent accelerations and repeated "whip cracking" of the belt. Laboratory investigations of the very high strain rates experienced by the belt during the whip cracking, show mechanisms for belt damage that are not associated with normal usage. This paper outlines the measurement to show that for long, low modulus conveyors, constant torque controls are inappropriate and time ramp controls are really essential.

Jan 1, 1998

By A. J. Getz

The paper reviews the status of the major precious metals projects in Australia, Papua New Guinea, Indonesia, the Philippines, and New Zealand. The projects may be at the stage of exploration, development, operation, or expansion. The paper covers project location, reserves, method of resource exploitation, anticipated production, and other unique conditions.

Jan 1, 1990

By L. M. English

A basic model was developed to help assess methane control needs for the longwall mining of coal in gassy areas. Rather than depending on reservoir and rock mechanical theories, it uses an empirically determined gas emission rate as an input, and it operates on the assumption that, within a specific region and zone, gas emissions will be relatively equivalent for uniform incremental volumes of gob created by mining. The computer program divides longwall panels into segments, keeps track of the face advance and generates emission rates and volumes for both the entire panel and for individual zones within the panel by summing values for all undermined segments. This model can aid in the determina¬tion of the number, size and location of vertical wells or other methane-control applications that are needed for gob gas control.

Jan 1, 2000

The Bureau of Mines has studied 260 underground coal mine fires which occurred from 1970 through 1989. Every fire had the capacity to be hazardous to life and property, however upon closer examination some were found to be inherently more dangerous than others. Our research involved reviewing and recording specific information contained in published Mine Safety and Health Administration fire accident reports. The objective was to determine if degrees of hazard relative to fire source or location could be construed from information contained in the reports. We specifically looked at the propensity for fires to cause injuries and fatalities as well as the need to seal the area in order to extinguish the fire. Relative to all underground locations, this review found that fires occurring in main haulage-ways were most likely to cause injuries and fatalities as well as require sealing of at least the immediate area to extinguish.

Jan 1, 1993

By Tad S. Golosinski

The paper presents the computing stream of the mining engineering curriculum at he Western Australian School of Mines (WASM), a branch of Curtin University of Technology. Learning to use computers begins during the first semester of the initial year of studies and culminates in the Mine Design Project done during the last semester of study. It covers all areas of computing which are judged to be of importance to the graduate.

Jan 1, 1996

By S. J. R. Lowrie, J. S. Edwards, A. D. Jones

A small scale model has been constructed to simulate air and gas flows on a full scale retreat longwall coal face. Scaling relationships were derived to define how the main aerodynamic properties of the full scale could be preserved in the small scale model. These scaling requirements include: a minimum value for the Reynolds number for the flow on the face in order to maintain turbulent flow with a constant non-dimensionalised coefficient of turbulent dispersion; a constant Richardson number to maintain similitude for the formation of layers of buoyant gas; scaling of the permeability of the waste so as to obtain the same proportion of seepage flow through the waste; pressure gradients due to the ventilation and to the density difference (between the air and the gas layer) were kept in proportion; and in the waste, the relative contributions of inertial dispersion and molecular diffusion were approximately in proportion. The complementary roles of computational fluid dynamics (CFD) and aerodynamic scale models for simulating mine ventilation are discussed. The physical model is described and an example presented of simulations of the effect of changes in mining condition on the effectiveness of gas control in retreat longwall coal faces.

Jan 1, 1995

By Michael Fahey, Ravi M. Damodaran, Brij M. Moudgil

The flotation behavior of Florida phosphates was studied using statistical design of experiments to evaluate conditioning parameters and their effect on flotation performance. The solids loading, conditioning time and agitation speed during conditioning were identified as the important variables affecting the reagent coating onto particles. Flotation of the conditioned slurry was carried out at fixed collector dosage and flotation conditions. Phosphate recovery upon flotation was statistically modelled as a function of the conditioning variables. The results indicated that the conditioning variables had an interactive effect on the phosphate flotation performance. Statistical optimization revealed two conditioning regimes in which optimum flotation recovery was obtained. It was determined that optimal recovery can be obtained at lower conditioning energies.

Jan 1, 1995

By M. J. Shields

There are numerous suggestions in the literature on methods of obtaining representative samples of waste rock or mill tailings. Some suggested methods would result in thousands of samples and very high costs for a large facility. There is no general rule that can (or should) be followed, such as collection of a given number of samples per mass of material, per acre of impoundment, or per foot of drillcore. Each site is different, and the adequacy of sampling must be tailored to the site. A logical approach is to let the variability at the site dictate the number of samples that should be collected and analyzed, and then to quantify and evaluate the results by means of standard statistical methods.

Jan 1, 1998

By L. G. Austin

Development of an equation for tumbling charge and balls plus comparison to plant data suggests that the net mill power for cylindrical semiautogenous mills can be calculated from

Jan 1, 1991

By J. W. Rinard

This paper is intended to introduce "non engineers" to one of the more misunderstood pump performance parameters, NPSH (Net Positive Suction Head). This basic presentation and resultant review should provide a practical understanding of NPSH and what its importance is to pump operation and reliability.

Jan 1, 1996

By Malcolm J. McPherson

Within the world of mining health and safety, increasing attention is again being given to underground fires and explosions. This paper reviews the effects of open fires in mine entries on the ventilation system, and outlines current methodologies of attempting to control such a fire. The particular hazards of a fuel-rich fire are discussed. There appear to have been no really significant advances made in methods of extinguishing mine entry fires in the last several decades. The final section of the paper introduces research that is investigating the simultaneous production of an inerting, cooling and quenching atmosphere by means of a dense water fog.

Jan 1, 1993

By P. N. Thompson

The past few years have seen the introduction of mini-computers on an increasing scale at collieries in the British coal industry. These are being used for controlling underground transport systems, coal preparation plants and fixed plant (pumps etc.); and for monitoring the mine environment and face operations.. A separate mini-computer (termed a primary computer) is dedicated to each of these functions. The overall system under which these computers operate is a common one which is applicable at all collieries. The information collected by the primary computers, other than that required for immediate control, will be fed to a secondary computer for analysis and processing. This overall concept, called MINOS. (MINe Operating System) is being developed by the National Coal Board's Mining Research and Development Establishment (M.R.D.E.). Eventually most of the data required by the system will be captured automatically. For example, the fact that a delay has occurred on a face, together with the duration of that delay, will be detected automatically via transducers link linked to a primary computer. However, the reason for that delay will, in all likelihood, have to be recorded manually. Such a system is currently under development with the first trial installations now being made.

Jan 1, 1979

By K. Tokutake

Kobe Steel, Ltd. improved the quality of iron ore pellets for blast furnace burdens when it enlarged its blast furnaces. However. there still remained room to increase reducibility at high temperatures for better blast furnace operation. In particular, it was still necessary to lessen the reduction retardation above 1200?C. In the last few years, by employing iron ore and additives of optimum size structure, large pore pellets with a high porosity have been obtained. By using this method. Kobe Steel. Ltd. has accomplished the technology to produce pellets with remarkably high reducibility.

Jan 1, 1989

By R. C. Ford, J. Kelsey, S. A. Pierce, M. D. Ankeny

Evaluation of acid drainage risk from spent (leached) ore in arid climatic zones consists of two components: (1) whether residual and secondary minerals will release acid and metals when exposed to rainfall, and (2) whether ambient rainfall is likely to infiltrate, and eventually impact surface or ground water resources. The risk of acid drainage from spent ore at the El Abra on-off copper leach pad operation was evaluated using conventional geochemical methods and unsaturated flow models. Although geochemical testing indicated poor quality water would result from any seepage, unsaturated flow modeling demonstrated that infiltration and seepage were unlikely given the arid climatic conditions. Modeling further demonstrated that the residual moisture content of the spent ore when it is removed from the leach pad controls the risk of seepage. To further reduce the risk of seepage, operational controls were developed and implemented at the El Abra site.

Jan 1, 2000