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By L. Darkwah

The use of explosives in coal mining inevitably results in oversize, midsize and undersize (fines) products due to fragmentation. The oversize can be broken into smaller sizes by further processing. However, the undersize have a negative affect on the efficiency of a mining operation. Therefore, limiting the amount of fines can be economically crucial. This paper concerns investigations aimed at reducing fines generation in coal mining. Inherent fractures were identified as one of sources of fines generation. This paper is centered on establishing a relationship between the fracture occurrence, the explosive properties and the blast outputs, which are evaluated in terms of the fines generated.

Jan 1, 1998

Information Technology has addressed those problems unique to senior management in the mineral industry. In general, these problems are those concerned with decision-making. Peter Drucker in his discussion of making effective decisions identifies five phases: (1) define the problem, (2) analyze the problem, (3) develop alternate solutions, (4) decide the best solution, and (5) convert the decision into effective action. The scope of the chapter by Guernsey addresses the first three phases which provide input to the decision-maker. The decisions to be made relate, in most instances, to the economics related to a mineral property or process. Computer models have been designed to generate these economic and financial evaluations. No one model is appropriate to the solution of all management's problems. In this chapter several applications are identified and summarized; a model for the economic evaluation of a mineral property is described in greater detail. The implementation of such models is dependent on the unique needs of management.

Jan 1, 1979

By R. Poulin, R. C. Pakalnis

Approximately 51 % of all ore production in Canadian underground metal mines is derived directly from open-stope operations. This method requires that large excavations remain open until the ore is extracted with a minimum acceptable level of dilution. A survey of underground mines in 1988 reported that a major factor in their closure was uncontrolled dilution. It has been reported that 40% of openstope operations were experiencing dilution in excess of 20%. This level of dilution has significant implications on the economic viability of a project, especially when one considers that a rate of return on a positive project is generally between 10% and 20%. This paper reports on the various definitions of dilution, on the methods of stope design that are presently used with the objective of reducing dilution and on a recently available survey technique that enables dilution to be quantified.

Jan 1, 1996

By Kai Nielsen

In underground mining coarse muck and large boulders lead to ineffective utilization of costly mining equipment, and extra expenses and delays caused by secondary blasting. Cost analysis in some Norwegian mines shows that these extra expenses may amount to 10% or more of total mine operating costs. A computer model has been developed for sensitivity analysis of underground longhole stope blasting. The basic idea of the model is : When increasing the blasting energy input and fragmentation costs, the fragmentation will be better. This will lead to cost savings for loading, hauling, secondary blasting and primary crushing. The blasting design giving the lowest overall costs will indicate the optimal practice. The model has been used with data from several underground operations in Norway. An example run with typical costs shows that the costs for drilling, blasting and secondary blasting are the most significant parameters in the optimization process.

Jan 1, 1986

By André Vien, Robert Edwards, Rob Perry

A metallurgical control application can only succeed if the system's lowest common denominator, its instrumentation and regulatory control is implemented and maintained correctly. This paper describes the basics of regulatory control implementation including some practical guidelines for instrumentation installation, operator interface design, loop tuning, and continuous loop performance analysis. Tuning and analysis techniques are illustrated by step-by-step industrial examples. A small investment in basic control pays dividends in better overall plant performance and provides a solid foundation for advanced control efforts such as expert systems.

Jan 1, 2000

By Peter A. Burger

The Greenvale Orebody comprises a series of contiguous lateriteprofiles developed terrace-like during the Cainozoic over a serpentinized harzburgite intrusive emplaced within Proterozoic schists. Each terrace displays individual characteristics of metal distribution. Topographically higher (older) profiles have been partially eroded and metal concentrations reworked. Within the laterite profile, metals have been concentrated or depleted according to their relative solubilities. At tropical temperatures, acidic meteoric waters have progressively depleted the ultrabasic parent rock of Si and Mg, leaving A1 and Fe to form a surface duricrust. Ni, Co, Mn and Cr have accumulated in the lower and middle levels of the weathering mantle. Only Ni and Co have accumulated to exploitable grades. Lateritization has evidently proceeded over a considerable portion of the Cainozoic and may be still continuing.

Jan 1, 1979

By J. Drelich, J. Pletka

Lost foam casting is a process in which a polymeric material is formed into the shape of the part to be cast. Parts that are more complex are fabricated by simply gluing several patterns together. The pattern is then coated with a refractory material consisting of a mineral mixture and binders. Finally, hot metal is poured into the pattern, evaporating the expanded polystyrene and taking the shape of the coating shell. Prior to casting, a significant number of the patterns are damaged and inevitably landfilled. In this study, a process was developed for the recovery of expanded polystyrene from the coating and glue contaminants. The process consists of shredding, impact comminution, size classification and pneumatic separation. It is successful in separating up to 97% of the contaminants, while recovering 95% of the polystyrene. Key words: Casting, Lost foam process, Expanded polystyrene recovery

Jan 1, 2003

By H. Sis, S. Chander

The beneficial effect of a series nonylphenol polyethylene glycol ether surfactants were tested in the flotation of phosphate ores in which the mixture of sodium oleate and dodecane was used as collector. The performance of nonionic surfactants was first tested in the microflotation of pure apatite mineral. Microflotation experiments showed that the recovery of apatite depends on the number of ethoxylation of the nonylphenol surfactants and decreased with higher ethoxylation. The nonionic surfactant with the smallest ethoxylation group used in this research (NP-4) was then tested in batch flotation of phosphate ores. The flotation of three different size phosphate ores was carried out in the absence and presence of NP-4 surfactant. The beneficial effect of nonionic surfactant was obtained for fine size (-35+150 mesh) and very fine size (-150+400 mesh) phosphate ores at different collector dosages studied. But, in the flotation of coarse size (-16+ 35 mesh) phosphate ore the beneficial effect of nonionic surfactant was obtained only at high collector dosages.

Jan 1, 2002

By Richard R. Klimpel

This paper discusses some important industrial interactions between size reduction and downstream froth flotation processes. Experience gained at the industrial level is clearly indicating that how size reduction circuits are designed and/or operated can have a significant impact on froth flotation beyond normal considerations of particle size, liberation, etc. Three specific interactions will be discussed: 1) the impact of steel grinding media versus autogeneous grinding on the efficiency of sulfide mineral flotation with varying thiol collectors and water sources; 2) the importance of appropriately utilizing the electrochemical window that is created in the grinding to enhance sulfide mineral recovery by froth flotation; and 3) the interaction of particle size distribution with collector dosage and frother type.

Jan 1, 1995

By George H. K. Schenck

Decisions to develop deposits of calcareous materials for cement production are based largely on anticipated markets for heavy construction which utilizes concrete. The geologist should understand the fundamental factors that underlie such management decisions, so that his field work and reports will more effectively relate to the information requirements of managers in the cement industry. The paper examines the relationships that exist between exploration and development of calcareous raw materials for cement manufacture and changing factors in the marketing of cement. Continued overcapacity, improved technology, changing distribution patterns, ease of entry, economics of scale, and the nature of product demand are some of the characteristics of the cement industry that are basic to decisions regarding exploration programs and property development.

Jan 1, 1966

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 R. Sivamohan, F. Huang

A mineral processing strategy developed for the finely and complexly interlayered calcite rich wollastonite, microcline, and iron-garnet ore of Jokkmokk, northern Sweden, gives an overall calcite recovery of 89.4% at a grade of 90.7% CaCO3. The wollastonite product assays 53.0% Ca- SiO3 at a recovery of 92.2%. The significant elements of the developed strategy are stepwise grinding, wet high intensity magnetic separation (WHIMS), reverse flotation and starvation flotation. Stepwise grinding avoids the overgrinding of soft calcite. WHIMS removes the colored iron-garnet impurity and thereby increases the whiteness of the product. Reverse flotation enables a simple flotation circuit and starvation `flotation helps to optimize the physicochemical conditions in cleaner flotation by giving rougher products of narrow particle size distributions. Moreover, with the reagent scheme developed in this work only one cleaner stage is necessary for the various rougher flotation products to be upgraded to give the foregoing results. In this paper, the strategy is presented in detail along with appropriate results.

Jan 1, 1990

By Jorma Miettunen

The Plant. The annual production of the Pyhasalmi mine is 900 000 tons of copper- zinc-pyrite ore containing approximately 0.7 % Cu, 2.5 % Zn and 30 % S. During 1976...1981 altered surface ore, 850 000 tons in all, was also treated at the concentrator. The surface ore was crushed and ground in a separate plant and was then fed into the copper or zinc flotation or was flotated in its own circuit, depending on the degree of alteration and the content of copper and zinc in the ore. The surface ore was exhausted in October 1981. Flotation comprises three consecutive flotation circuits; copper, zinc and pyrite circuit. The zinc circuit includes an open circuit roughing and scavenging. The scavenger concentrate and cleaner tailing are pumped to the middlings flotation. Rougher concentrates of the open circuit and the middlings flotation are pumped to cleaning which includes four stages. Figure 1 describes the flowsheet of the zinc circuit.

Jan 1, 1982

By J. E. Rourke, O&apos

This paper describes the use of index testing to obtain rock properties that are useful in the design and construction planning of an underground development for civil engineering or mining projects. The index properties discussed include: point load; Schmidt hammer hardness; abrasion hardness; and total hardness. The first two index properties correlate to uniaxial compressive strength (UCS) and Young's modulus. Discussions are given on empirical, normalized relationships of UCS to rock mass properties and the integrated use with semi-empirical, geotechnical design methods. The hardness property indices correlate to construction performance parameters and some relevant experience is cited. Examples of data are presented from an index testing program carried out primarily on siltstone, sandstone and limestone rock core samples retrieved from depths up to 1005 m (3300 ft) in a borehole drilled in the Paradox Basin of eastern Utah. The borehole coring was done for a nuclear waste repository site investigation.

Jan 1, 1990

By Derek G. Cieplinski

Regenerative conveyors with complex conveyor profiles place unusually stringent demands on the starting drive control. Depending on the nature of the conveyor loading, the drive must either provide a positive driving force to overcome conveyor friction and gravitational forces if the belt is empty or the inclined sections are loaded, or it must provide a retarding force to resist the gravitational load of decline sections to control the acceleration rate. This paper discusses the requirements of regenerative conveyors, reviews the working principals of fluid couplings, and examines their interaction by means of a case study of a 1700 m long regenerative conveyor utilizing a fluid coupling with a proportional brake control to provide controlled starting and stopping under all load conditions.

Jan 1, 1993

Cost accounting information is used primarily for (1) planning, control, and performance evaluation; and (2) managerial decision-making. Incremental analysis is a tool for managerial decision-making. It is designed to estimate future financial performance, namely the benefits and costs associated with alternative courses of action. Decisions may be distinguished as pertaining to short-term or long-term activities. Long-term activities frequently focus on capacity decisions and the attendant capital budgeting processes used to quantify the financial effects of these decisions. Short-term decisions typically address short-range production quantity and pricing issues, outsourcing, selection of the optimal mix of products, inventory management, and the acceptance of special orders. This chapter addresses these short-term decisions.

Jan 1, 1999

By M. H. Kotze, M. J. Virnig, G. Steinbach

Earlier work at Mintek on the development of gold-selective resins culminated in a plant-manufactured batch of the first generation of Minix resin. A subsequent pilot-plant campaign at a South African gold mine identified some problems with that resin. These included lower capacity and selectivity for gold compared with the laboratory prototype, and a slow but progressive loss in capacity as the resin was eluted and reloaded cyclically. These problems were overcome by chemical modification of the resin structure. Examples of these improvements are presented. The commercialization of a new resin for a new metallurgical application presents problems, which are exacerbated by the initial lack of demand for the resin because the process is unfamiliar to the mining industry. Progress in the commercial development of Minix is discussed in this context.

Jan 1, 1993

By Patrick Linzer

The majority of existing models describing (methane) gas transport within, and liberation from, coal structures treat these as continua wherein two main gas flow modes (diffusive and Darcy permeable) prevail, and use finite difference techniques to generate solutions to the resulting multivariate parabolic partial differential equation(s). Isotropy and homogeneity in the physical and geometric coal structure properties are often assumed, and the existence of fundamental random fluctuations in these proper- ties is not catered for. The model proposed herein does not suffer these inadequacies, and its efficiency is enhanced by the replacement of the diffusion equation by an accurate approximation. Dynamic mining activity, gas contributions made by the geology surrounding the mining seam, goafing of overlying strata and the effects of induced strain are all taken into account.

Jan 1, 1995

By David Sugden

Intense, tropical weathering of Cretaceous-Tertiary sediments has developed similar laterites in distant areas of the Amazon Basin. In two areas, Trombetas and Paragomina s, bauxites of commercial potential arc found. The bauxite comes mostly from the lower horizon of the three component laterite. The laterite is overlain by a clay cover, possibly an integral part of the weathered profile. The laterites are found on almost flat plateaus with individual areas of up to 80km2. There is a close relationship between the morphology and the ldterites. The process of lateritization is allegedly Pliocence but probably continues today.

Jan 1, 1984

By Peter J. Suardini

Over the last few years, researcher have been working on improving procedures for fine-coal (minus 150 microns) washability analyses. The effort was stimulated by past difficulties in obtaining accurate and reproducible results from the various commercial laboratories providing fined washability services. This paper contains the results from fine-coal washability testing, performed by Process Technology, Inc. (PTI), as part of a U.S. Department of Energy (DOE)-sponsored project. The testing focused on comparing the performance of a number of media options (i.e., aqueous solutions and organic solvents), as well as evaluating the impact of a number of procedural steps on separation performance. The paper summarizes PTI's recommended washability procedures for various size fractions and ranks of coal, and makes recommendations for future studies of certain phenomenon, such as void penetration and particle density changes, which are not well understood.

Jan 1, 1995