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By Kenneth J. Reid

The application of computers for control purposes in hydrometallurgical processes is not as well-established as in mineral processing plants. This is not only due to the comparatively new development of large-scale application of hydrometallurgy and the relatively small number of operating plants, but also due to some of the basic dynamic characteristics of hydro- metallurgical processes., Basically there is little difference in the development and application of digital control techniques in hydrometallurgical plants from those techniques widely in use throughout the chemical process industry and in nonslurry applications; particularly for those cases involving liquid streams only, the primary sensing elements are essentially the same. On-stream X-ray fluorescence analysis is a well-established method for determination of metal content in the process streams, and standard equipment is used for the measurement and control of pH, flow, density, temperature, pressure, and other variables. Nevertheless, the high proportion of corrosive slurry streams at elevated temperature and pressure poses a challenge to the instrument engineer concerned with developing long-life, reliable instrumentation. One major difference and potential problem area in developing control systems for hydro- metallurgical processes is related to the very long time constants which are common in the larger plant. In these circumstances, it is important to define the overall control objectives very carefully and be prepared to allow for considerable drift in intermediate variables. In larger projects with many control loops the general advantage of lower costs compared to conventional analog instrumentation can be confidently expected. Also in most cases, the process analysis necessary to design and specify a comprehensive computer control system and the increased operator involvement in implementing digital control systems yield additional benefits due to the increased understanding of the dynamic characteristics of the process.

Jan 1, 1979

By D. Malhotra

Gold and silver ores are generally leached in weak cyanide solutions for recovery of precious metals. However, pretreatment of refractory ores requires flotation to concentrate the precious- metal minerals. Also, flotation is a common concentration technique for recovering precious metals as byproducts in sulfide-mineral flotation circuits. The present paper reviews current plant practice and future challenges for precious metal recovery.

Jan 1, 1999

At periodic intervals-typically at the end of each month, quarter, and year- the accounting department in each division of a company distributes a set of reports to the division's managers. These reports describe the financial performance of the division and its major departments over the time period. They identify the revenues generated from the division's products and the costs incurred in their production. The results from individual departments are combined to determine divisional results, and the results from individual divisions are in turn consolidated to determine the results for the overall corporation. Cost reports for each of these activities show actual amounts, budgeted amounts, and the differences between the two. This reporting is carried out for the individual period and for the year to date.

Jan 1, 1999

By Zhen-lu Zhao

The manipulators possibly used in underground mining must deal with unpredictable obstacle while keeping certain positions and orientations of end effector, and in some cases, are required to possess redundant joints in order to be more flexible. This kind of manipulators might be fitted with jumbo drill or platform as auxiliary to potentially deal with some utility works in versatile way, such as installing rock bolts, guniting, blasting, charging, surveys and measuring work, etc.. This paper describes numerical procedures of performing inverse kinematic problems for redundant manipulators .The procedures, based on the generalized pseudoinverse of Jacobian matrix, are developed to lead to kinematic solution at both singularity and ill conditioning, and to guarantee continuous sequence of positions of the end effect or. Furthermore, the solution to optimization and obstacle avoidance is investigated. A numerical example is shown to illustrate the approach.

Jan 1, 1989

By A. S. Polubinsky, V. P. Chernyak

A further development of the theory of heat- and mass transfer in the system “strata - mine opening" is necessary for an improvement of the existing technique of heat calculation of mines and other underground constructions. A generalized boundary problem of heat- and mass conduction in strata around an opening as a theoretical ground for that purpose and several particular situations, important from the point of view of an opening and surrounding strata heat state analysis, as well as results of numerical experiments executed for such analysis are presented.

Jan 1, 1997

By P. R. Bailey

The use of carbon for the recovery of the gold dissolved in cyanide leaching began with a pilot unit at Barberton in 1977. This was quickly followed by larger scale plants at Modderfontein (1978), President Brand (calcine 1980), Western Areas (filter tails 1980) and Beisa (primary ore 1981) and has grown to become the preferred process. There are currently 34 operations that use the carbon in pulp/leach process which accounts for 35 percent of South Africa's gold production. The size of individual plant varies over a wide range.

Jan 1, 1993

By G. Milojcic

The opencast lignite mines in the Rhinel and Di strict/Germany are equipped with the continuously operating bucket-wheel excavator - conveyor - spreader system. High productivity requires large capital expenditure on main mine equipment as a precondition for efficient mining. In operation, the technology employed leads to a particular cost pattern which is quite different from that of other industries. Labour, auxiliary equipment and mobile vehicles are the most important cost factors which can be controlled by the management. In this respect information processing computer systems are used for systematical and interpretable representation of operational tasks and jobs both in planning and work preparation and in recording the operational data describing the work result and the use of resources. Another aim of the project is to relieve the middle management of major part of its administrative routine work. Job-related work planning and data recording open up various possibilities of analyzing the operational procedures. This analysis shows, for example, what auxiliary machines are particularly suitable for specific tasks, and working groups can be organized so as to take account of the different skills of individual employees for the sake of an optimal work product. Computerized information processing provides the decision makers with topical information related to their respective responsibilities. The mining department of the Hambach opencast mine is the first user of the PERMAD system. Due to the favorable evaluation it has been decided to introduce PERMAD in three other mines in the course of 1992/93.

Jan 1, 1992

By Dean J. Soderstrom

Soil and sands were contaminated with depleted uranium from weapons testing. This resulted in the formation of a complex mixture of uranium compounds. Characterization studies of the soil indicated the uranium was present as uranium metal, uranium oxides, silicon-bearing metallic uranium, and uranium silicates. A process was developed to selectively remove dense uranium compounds using gravity separation and a chemical extraction system to remove uranium which was not available for separation by gravity methods. Results from characterization studies and pilot scale testing are presented for background information. The primary purpose of this presentation is the report of the results achieved in the field application of the processes.

Jan 1, 1995

By R. Larry Grayson

A menu-driven, linear-programming- based, user friendly computer program was developed to assist mine managers in determining optimal longwall panel dimensions for a given set of operating conditions. A sensitivity analysis must be performed by varying key mining and configurational parameters over an expected, practical range during the optimization process. Results from analysis of a base case mine indicated that no single combination of longwall panel length and face width is optimal for all operating situations. Each mine manager must therefore look closely at his operating situation and determine the proper dimensions to minimize total mining cost.

Jan 1, 1989

By R. V. Ramani, S. Tan

In this paper, several commonly used computer truck-dispatching criteria are evaluated. A computer-oriented truck-dispatching and production simulator was developed to provide data for comprehensive cross comparison among the dispatching criteria. The definitions, primary considerations, characteristics and performances of these dispatching criteria were investigated. From the simulation results, it was concluded that, in general, no one criterion can dominate all others. However, several dispatching criteria that have good potential to increase performance can be identified. All basic dispatching criteria, including minimizing truck waiting time, waiting shovel with minimum waiting time, minimizing truck saturation, maximizing truck momentary productivity or optimization of truck routes, provide local optimal solutions. To obtain a direct global optimization solution for this complex stochastic process does not appear to be likely Therefore, the search for an optimal dispatching criterion that will fit all conditions may not be realistic. It may be necessary to search for a hybrid combination of the several truck dispatching criteria that have good potential for a given situation. An approach to selecting such a hybrid dispatching criterion is presented.

Jan 1, 1993

By Waclaw Dziurzynski, Janusz Tracz, Danny Wooton, Andrzej M. Wala

The purpose of this paper is to present validation studies of the mine-fire simulator using data gathered from an actual mine fire which occurred in November 1991 at the Pattiki Mine. This study evaluates the suitability of the computer software package for modeling underground fires. The paper also discusses the importance of the on-line monitoring system for the validation process.

Jan 1, 1995

By S. K. Kawatra, T. C. Eisele

To reduce their sulfur emissions, many coal-fired electric power plants use wet flue-gas scrubbers. These scrubbers convert sulfur oxides into solid sulfate and sulfite sludge, which must then be disposed of. Currently, the major markets for scrubber sludge are for manufacture of gypsum products, such as wallboard and plaster, and for cement. However, the quality of the raw sludge is often not high enough or consistent enough to satisfy manufacturers, and so the material is difficult to sell. Other markets, such as paper manufacture and plastics fillers, have even more stringent quality requirements and will not accept raw sludge at all. In the work described in this paper, several reagents have been examined to determine their ability to selectively improve the flotation of the unreacted limestone contaminant away from the desirable products (calcium sulfite and gypsum). The most success has been achieved using a cationic collector, which shows a higher selectivity between calcium sulfite and calcium carbonate than do the anionic collectors that were studied.

Jan 1, 1995

By Louise H. Michaud

An interactive mine planning system that employs recent advances in 3D computer graphics capabilities and 3D geologic modelling to aid with the tasks involved in producing dragline mine plans was developed. As well as offering large potential saving in the time required to carry out the planning tasks, the system offers immediate visual feedback to the planning engineer. This can greatly aid in the conceptual understanding of complex geology and mine plans. The package incorporates the generation of a three dimensional Gridded Seam Model (GSM) as the basis for the development of the geologic database. This modelling method is capable of accurately representing rugged topography and multiple coal seams, including folding and faulting. The GSM is then integrated with an interactive graphics mine planning system in order to develop one model and one database for the generation of the mine design, the depletion of the coal resources and the movement of spoil material. The gridded structure of the model also provides the foundation on which all mine and spoil pile volumes are calculated.

Jan 1, 1992

By C. R. Euston, B. T. Field, W. E. Lindquist

Pyroprocessing applications in the minerals industry range from low-temperature drying to high-temperature reactions. Material characteristics and process requirements range over a very broad spectrum and can confuse plant engineers trying to select a pyroprocessirtg system for their plant. This paper examines the important process variables and offers empirical guidelines to assist in a user's overall process evaluation.

Jan 1, 2000

By Paul Gribbon, Greg Colzani, Jim McDonald

The $300 million West Side Combined Sewer Over?ow Project consists of over5.5 kilometers of soft ground tunnel, an 833-million liter per day (220-MGD) deep shaft pump station, 3 kilometers of micro tunneling, and other miscellaneous shafts and pipelines. The construction contract, underway since September 2002, is a reimbursable cost plus fixed fee contract that included a quali?cations-based contractor procurement process and has undergone some modi?cation since execution. This paper will describe the contractual issues addressed to date, dispute resolution, where improvements can be made, and how an Owner can evaluate whether this type of contract is the best approach for an underground project.

Jan 1, 2005

By Mary B. Ansari

The literature of mine ventilation is very diverse in nature, widely interdisciplinary, and extremely international in scope. Important references are found in indexes, abstracts, government documents, technical reports, journals, conference and symposia proceedings, and monographs. In this decade computer searches of the literature have greatly aided researchers in finding needed items. There is, however, no convenient summary of recent English language literature in coal and non-coal mine ventilation. This paper attempts to fill that gap in the literature. Because of the worldwide provenance of the subject and the attendant publication deluge, this paper covers only current English language publications on ventilation. The writers have examined the field's English language abstracts, indexes, bibliographies, periodicals, technical reports, books, and symposia and conference, proceedings. The survey also considers the field's most important bibliographic data bases. It should be noted that addresses for many of the literature sources listed in the paper are given in the section on literature and data base information sources.

Jan 1, 1980

By G. M. Wilemon, J. G. Davis, R. G. Swanton, B. J. Scheiner

The US Bureau of Mines has conducted investigations on extracting phosphate values from wastes generated during the mining and beneficiation of phosphate matrix. These wastes may contain up to one third of the phosphate originally present in untreated ore. Samples of wastes were air-dried and leached using 93% sulfuric acid in the presence of methanol. Evidence for the formation of a calcium sulfate hemihydrate coating that hinders complete dissolution of phosphate is presented. Solid-liquid separations were enhanced when flocculation was effected using poly(ethylene oxide) (PEO) in conjunction with hydroxypropyl cellulose (HPC) or hydroxyethyl cellulose (HEC). A conceptual flowsheet for a proposed process using an acid-alcohol leaching technique is presented.

Jan 1, 1991

By G. T. Adel

Hindered-bed separators are often used in the minerals processing industry to classify particles according to size and density. A new technology, known as the Eriez CrossFlow, was recently developed to overcome some of the limitations associated with hydraulic separators. The innovative feature of this unit is a novel feed presentation system that improves separation efficiency and capacity. In the present work, a detailed process engineering evaluation was conducted to determine the basis for the improved performance of this unit. The evaluation included controlled separation tests using well-characterized feeds, particle and liquid tracer experiments and mathematical modeling studies. Data obtained from this work show that the new separator is capable of maintaining good separation efficiencies at higher solid feed rates than traditional designs due to improved hydrodynamics in the separation zone. This paper reviews the operating principle of the Eriez CrossFlow separator, discusses the results of the tracer experiments and modeling studies and presents test data obtained from recent laboratory and plant trials. Key words: Size classification, CrossFlow separator, Hindered-bed separator, Hydraulic separator

Jan 1, 2003

By C. Haycocks

In spite of the increasingly high capital investment required for longwall mining equipment, there continues to be a steady trend towards this form of mining. This move is caused in large part by improved productivity of longwall mining systems combined with greater percentage of coal recovered over room and pillar mining, reduced manpower requirements, and the inherent safety of the system. Longwall mining is most amenable to the greater depths experienced by many mining operations, particularly in the coalfields of the Eastern United States. Two primary problems in the installation of a longwall panel are determining whether a particular seam is suitable for longwall and, secondly, type and capacity of equipment required for such a mining operation. In addition, recent legislation has forced an evaluation of the surface effects of longwall mining with a view to determining what, if any, surface damage might result from extracting any particular panel. These factors must be determined using large and often complex quantities of geological, structural, mining, and surface data. This makes the problem most attractive to solution using the computer.

Jan 1, 1979

By Paul D. Chamberlin

The evolution of heap and dump leaching has followed the development of agglomeration, materials of construction for leach pads and ponds, solution distribution systems, testing techniques, and state regulations. They are now mature processes. Possible future directions and developments are discussed. In situ leaching of precious metals is waiting to be commercialized. Regulators are reluctant to allow the use of cyanide because of the potential for excursions and operators are reluctant because of the potential for lawsuits. Developments in alternative lixiviants are needed before in situ leaching is accepted.

Jan 1, 1989