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By I. Shah, L. G. Austin

A method for quantitative investigation of the phenomena involved in fine grinding of materials that follows the changes in the breakage rates of fine particles has been presented. For relatively hard, brittle, non-coating material like quartz, the slowing down effect of breakage rates starts to be significant at relatively coarse sizes, which goes often undetected in closed circuit grinding systems, producing relatively coarse product, say P80=75µm However, for fine grinding systems, as the -10µm fractions begin to build-up, and classification becomes more difficult, the build-up of fine sizes causes a slowing down effect Compounding this problem is the difficulty of obtaining accurate cumulative weight size distributions in the fine size region.

Jan 1, 1983

By V. K. Karra

Research by various workers has shown compressive comminution to be significantly more efficient than impact comminution. Based on the work being done at Nordberg, wet compressive crushing in cone crushers producing finer and finer products, shows the feasibility for partial substitution of conventional tumbling mills. For further substitution, major challenges are processing of fine feed slurries in cone crushers to realize a significant size reduction of the particles, and understanding the limitation of the gyratory type units in terms of finest product achievable. The paper addresses the challenges involved, efforts at Nordberg, and the implications to conventional comminution flowsheets.

Jan 1, 1989

By Tim Wolf, Barry Fink

Mine site managers reported occurrences of locking assembly bolt failures on the Enlow Fork Coal Mine's slope belt conveyor. The observations were made after a number of years of operation and raised questions as to the status of the assemblies in operation. These questions prompted a detailed review of the situation by independent consultants. Using operational history of the conveyor and confirmation of belt loads by static and dynamic methods, a locking assembly fatigue curve was created to suggest expected service life. From this work, suggestions were made to modify the pulley assemblies for extended service life.

Jan 1, 2002

By Lei Chen, Michael L. Free, Ravindra Bhide

The incorporation of particles into metal matrix materials is important to many technologically important areas. Particles that are incorporated into a metal matrix have a significant effect upon the properties of the resulting composite. Proper selection of particles and incorporation densities can lead to optimal composite properties that can be modified as needed for various applications. This paper discusses the parameters that affect the particle incorporation density in electrodeposited metal matrix composite coatings as well as a deterministic model that can be used to predict the effects of such parameters on particle incorporation density.

Jan 1, 2003

By S. C. Bandis, N. Barton

During drilling of deep boreholes, local mechanical failures of the wellbore walls may occur due to the inability of the incompetent overburden and reservoir rocks to withstand drilling-induced changes of the stress environment. At present, borehole failure mechanisms in three-dimensional stress fields are poorly understood. Our experimental investigations based on 3-D physical models demonstrate the stabilizing effect of the intermediate principal stress. The latter may play a dominant role in maintaining the integrity of the stress relieving failure zone around the borehole. However, this will depend on the stress anisotropy, the angle of hole deviation and on the angle of internal friction. Our tests also indicate that the failure zone can accomodate high extensional strains. Finally, relations between the physical models and closed-form elasto-plastic solutions are discussed.

Jan 1, 1986

By J. K. Mohanty, D. Panda, P. K. Sahoo, R. K. Paramguru, K. C. Nathsarma

Ferromanganese slag, a product of the manganese industry, was characterized mineralogically. The slag, which contains high Mn values, was characterized using optical microscopy, XRD analysis and electron microscopy. No separate Mn-bearing oxide mineral phase was found. The slag is amorphous, and no crystalline phase was identified in the hulk sample by XRD, However, in. fine fractions, quartz was identified. Scanning electron microscopy (SEM) revealed the presence of Mn, Si, Al and Ca in the matrix without the development of a mineral phase. Leaching experiments using H2SO4 were carried out to determine if Mn could be extracted from the slag. At room temperature, almost 100% of the manganese could be dissolved at a solid-liquid ratio o f 1:10 by leaching with dilute sulfuric acid. The impurities could be precipitated by pH adjustment to produce a manganese sulfate solution suitable for the production of MnO2 or electrolytic Mn metal. Based on the laboratory-scale experiments, a suitable process is proposed to recover manganese values from the, ferromanganese slag.

Jan 1, 1999

By Oscar Letelier Gonzalez

The goal of mine planning is to determine "the best" strategy to exploit an ore deposit during its workable life. Such strategy must be consistent with the objectives of the company and must be subject to the contraints imposed by economical, physical and geological conditions. Mine planning process may be broken down into three categories, according to the planning horizon: Long range, Short range and Operational. The shorter the scope of planning, the higher the level of details and the lower the degree of freedom associated to each plan. A long range plan defines the economic limit of mining at the mining life end of the deposit; it also can be used as an aid in the evaluation of the economical potential of a mineral deposit and as a guide for short range plans.

Jan 1, 1979

By James L. Crowe

Electric-power-generating plants fired by fossil fuels are faced with increasingly stringent requirements for control of sulfur emissions. Several approaches for limiting these emissions, or for operating such facilities in an environmentally acceptable manner, are being pursued. Some of the approaches are based on the use of naturally occurring carbonate rocks or of materials derived from them. This paper discusses primarily the carbonate-rock-based processes being developed for control of sulfur dioxide emissions from fossil-fueled electric-power-generating plants. It includes a discussion of the role of carbonate rock materials in removal of sulfur dioxide from stack gases after combustion, capture of gaseous SO2 during the combustion process, and removal of sulfur from fuel prior to complete combustion. Materials derived from carbon- ate rocks are generally used in processes which convert the sulfur to a throwaway product, but there are also proposed processes in which the sulfur is converted to a useful product and the absorbent is regenerated for reuse.

Jan 1, 1974

In a world dependent in part on the consumption of depletable natural resources, development of new areas of mineralization is a necessity for replacing those reserves. Exploration, which is the initial task of replacement, is an information-gathering process which supplies input for management decisions on mine development. If the demand for resources is the driving force of exploration, then the scientific basis for its pursuance is the hypothesis of anomalous mineralization in a metallogenic province, which is tested by measuring physical characteristics of natural phenomenon. The resulting data are reduced, analyzed, and interpreted to locate expressions or responses associated with possible ore bodies. The process is, in fact, repeated in ever increasing measurement detail to increase the accuracy and precision of information for decision making. Exploration ceases when management makes the decision to develop a mineralized area, to hold a property for more favorable market conditions, or to drop a property because it is not economically viable.

Jan 1, 1979

By Edita Vircíková, J. B. Hiskey, Ludovít Molnár, Peter Lech, B. J. Scheiner

This paper describes the results of a study of hydrometallurgical methods of producing sodium arsenate for the glass industry from arsenic oxide wastes occurring in carbon dioxide washing. This paper addresses the following aspects: theoretical assumptions for leaching arsenic and its oxides, experimental results of As(III) oxidation to As(V) in aqueous solutions, sodium arsenate crystallization (the system As2O5-Na2O-H2O), characteristics of the crystalline product, and pilot-plant tests using sodium arsenate in the glass industry.

Jan 1, 1993

By R. Fedors, T. Ghezzehei, D. Or

The phenomena of dripping into cavities (e.g., tunnels and drifts) within an unsaturated fractured porous medium under ventilated conditions was studied to improve estimates of dripping rates, drop sizes and the chemical composition of droplets that could affect the integrity of high-level nuclear waste packages placed in drifts. The sensitivity of dripping rates and water chemistry to ventilation was analyzed at various flow rates using analytical expressions linking flow on fracture surfaces to drop formation and evaporation. The model was tested using laboratory experiments involving machined aluminum slabs designed to represent a simplified morphology of a fracture face intersecting a cavity and using natural fracture surfaces from a welded tuff Comparison with ten years of data on dripping in natural caves showed good agreement with model predictions. In particular, for low dripping rates, evaporation due to ventilation leads to larger drop sizes and alters drop chemistry by increasing the concentration of solutes in the drop relative to that in the water flowing on the fracture face.

Jan 1, 2002

By V. Srajer

The Calgary Coal Research Laboratory of CANMET and the National Research Council in Ottawa are developing a series of computer models aimed at improving productivity and operational practices of the Canadian surface coal mining industry. One of the top priorities in this respect is a comprehensive computer model of truck/shovel system. A total of twelve mining companies supplied data for validation purposes. The supplied data, operating practices and variances of individual mining systems from the general version of the computer models are discussed in the paper. A short overview of the truck/ shovel model and a plan for future activities involving the application of the computer models for simulation of mining practices are also described. The presented paper summarizes the experience gained during the collection of data for the development and validation of the model.

Jan 1, 1986

By P. J. Ryan

December 1988, Phelps Dodge Corp. brought an underground gold mine into production in the republic of Botswana. The mineralization is associated with steeply dipping shear zones in Archean greenstones of the Tati schist belt. The gold is intimately associated with sulfides and is refractory in nature. The deposit is being exploited by underhand open stoping methods. Vertical and inclined shafts are used to hoist the ore to the surface where it is treated by conventional crushing, milling, and flotation, followed by fluid bed roasting with cip elution and carbon regeneration. Adjacent deposits are being explored with a view to increasing production. Legal and taxation aspects of operating in Botswana are discussed.

Jan 1, 1991

By B. Whitmoyer, J. Tian, J. E. Sneckenberger, M. A. Jerabek, C. A. Chandler

A computational procedure has been developed to determine the lung volume function for the upper airways of the human respiratory system. This analytical procedure computes a person's partial lung volume from an experimental two-microphone acoustic measurement of the upper airway passages obtained through a molded tubular mouthpiece. The theoretical transfer function for the two microphone signals as well as the related acoustic impedance and reflection coefficient for the upper airways are calculated using two-channel spectrum analysis techniques. An inverse spectrum analysis scheme then converts the reflection coefficient to an impulse response from which the airway area function is extracted using an area recovery algorithm. Numerical integration of the upper airway area function yields the lung volume function for the upper airways of the human respiratory sysytem. A software program to accomplish this computation of human upper airway volumes will be described in this paper. Application of this computational procedure to the measured tracheal acoustic impedances of 15 human subjects will illustrate the program's capability toward early detection of lung dysfunction using a prototype clinical facility.

Jan 1, 1991

By J. C. Yingling, G. T. Lineberry

A control system for reducing peak loads on mine conveyor networks is proposed. The system involves continuous monitoring of flows into the conveyor network and section feeders with variable discharge capability. The control strategy uses differences in material transit times from various production units to the transfer points in the network to forecast load levels that will he intersected by the discharge of the controlled feeders over future time intervals. Feeder setpoint adjustments are made to prevent excessive peaks in the combined flows at the transfer points, while maintaining adequate feeder through flow to avoid production bottlenecks. Simulation studies suggest that the control strategy would be very effective in reducing capacity requirements of gathering belts.

Jan 1, 1993

By N. C. Saxena, S. K. Puri, A. K. Pal

The condition-based monitoring system is an important innovation for reducing the downtime of costly, heavy earth- moving machinery (HEMM). Vibration severity measurements were made on the HEMM located at the Gevra Project, the largest coal opencast project in India. Whenever the vibration severity levels exceeded the permissible limits, necessary actions were taken to replace the defective parts of the ma- chine. The systematic vibration monitoring of 120-t (132-st) dumpers, followed by corrective measures led to a substantial increase in component life (8.18% for an 445E Dressor and 28.44% for an MK-30 Unit Rig). The associated costs (including spareparts) were reduced by 21.55% and 25.74%, respectively. Because of the reduced downtime, savings for these two dumpers over the period from March 26 to June 25,1998, were of the order of Rs.26.47 (US$0.649) million.

Jan 1, 2000

By B. D. Shah, H. S. Soto

Lack of selectivity in mixed mineral flocculation can be attributed to one or more of the following factors: dissolved ion interference, hetero- coagulation, mechanical entrapment in flocs, and entrainment of fines between flocs. In a study of the apatite-dolomite system, it was determined that dissolved ions do not have a significant effect on selectivity. Heterocoagulation was minimized by choosing proper process conditions and addition of a dispersant. Mechanical entrapment was proved to be insignificant and efforts were made to reduce entrainment by choosing an appropriate method of separation of flocs from fines. A new factor termed "polymer induced entrapment," which occurs due to limited affinity of the polymer to the mineral that is not flocculated, is postulated to be the cause for the loss of selectivity.

Jan 1, 1988

By P. Somasundaran, C. C. Harris

The power consumption of stirred-media mills was studied using an approach developed from work on stirred reactors. Evaluated were the relationships of factors such as stirring speed and impeller and tank dimensions on the torque required to rotate disc and pin impellers immersed in dense particulate media. Data collected under carious experimental conditions were analyzed. The results were summarized and presented in the form of characteristic plots, general equations and dimensionless group correlations involving power and modified Reynolds numbers. Special attention was directed towards the rheological properties of the media, which was considered a non-Newtonian liquid, and hence the equation of power-law liquids was employed. A procedure for estimating the parameters of effective viscosity and scale-up guidelines (with respect to power consumption) are proposed.

Jan 1, 1996

By J. G. Groppo, J. G. Justice, B. K. Parekh

Removal of particulates and/or metal ions from mineral/coal processing waste water is a necessity from the environmental point of view. This paper describes application of a novel AC- electrocoagulation technique to remove the particulates as well as metal ions using AC power. A series of laboratory tests conducted on a stable black water sample obtained from a sub-bitminous coal operation provided a clear supernatant (-10 NTU) from the suspension. The process also shows promise in removal of up to 90 percent of phosphate ions and other metal ions (copper and nickel) from solution. A preliminary economic evaluation of the process will also be included.

Jan 1, 1992

By Hector M. Valenzuela, Juan H. Rojas

This paper presents a strategic plan for automation, plant integration and process management being implemented at the Chuquicamata mining and metallurgical complex of Codelco-Chile. This five-year plan considers different levels of process control and plant integration, which include instrumentation and direct control, process models and supervisory control, plant information integration, and real time process and plant wide management. The conceptual solution developed defines an architecture for the overall system and the projects to be implemented by each production unit, as part of the proposed solution for the division wide process control, plant integration and real time process management. An estimate of the cost benefit relation of the plan is also given.

Jan 1, 1998