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By L. Adler

A fairly complex analysis is required to select, or evaluate a piece of excavating and bulk handling equipment and obtain its performance. At present there is little agreement as to what specific points should be considered, and even less on what procedure to follow. This paper provides both of these in a consistent and direct form. The analysis applies to all types and sizes of equipment from the bulldozer and the continuous miner, to the B.W.E. The importance of the equipment characteristics, job activities, and work conditions are stressed and separate analytical stems are established in a flow chart for these. They are combined using suitability tests in the following steps: 1) problem statement, 2) natural conditions, 3) suitability guidelines, 4) appropriate equipment types, 5) operational activities, 6) encumbered space, 7) geometric design, 8) equipment sizing, 9) failure and limits, 10) performance and consumption, 11) public policy checks, and 12) costs and profitability. Public policy and economics while considered throughout receive emphasis towards the end. The procedure is iterative, containing distinct feedback loops. Specifying the steps and sequence provides a necessary structure which has long been overdue.

Jan 1, 1983

By E. G. Loesche

Grinding mills in which the comminution takes place between rollers and the surface of a disc, table or ring are generally known as roller type mills. The Loesche Mill, also known as the Disc Roll Mill, is a special type of roller mill in which the grinding surfaces consist of two rollers assembled over a horizontal disc or table which rotates at a relatively low speed. This design is particularly applicable to industry's present day demand for large capacity grinding mills.

Jan 1, 1964

By Aydin Shaterpour Mamaghani, Cemal Balci, Nuh Bilgin, Mucahit Namli, Hanifi Copur

"It is expected that more than 10 Billion USD will be spent in Istanbul in coming years on tunnel boring especially with EPB-TBMs. However, the geology of Istanbul is very complex. Geologic formations changing from Paleozoic to Cenozoic ages cause tremendous problems due to frequently changed rock formations and andesite and diabase dykes. This paper summarizes a universal model to predict the performance of EPB-TBMs which is created upon the data base collected from several projects. The model first is based on predicting field specific energy and power consumed of TBMs using geo-mechanical properties of the excavated material and TBM diameter. Later net production rate is calculated using field specific energy and power consumed by TBM. A methodology to predict machine utilization factor permits to calculate daily advance rates. The validity of the model is tested using the data obtained from two recent metro tunnel projects. 1. INTRODUCTION It is expected that in a near future a total length of 400 km will be excavated in Istanbul in a complex geology. Selecting proper tunneling equipment, organizing an effective operational management with the right tunneling crew will be a major concern for an efficient scheduling of the future projects necessitating to create a model to estimate daily advance rates. Several TBM performance prediction models with few on the prediction of machine utilization time were realized in the past. However, there is quite limited number of research studies on predicting the performance of EPB TBMs. Specially predicting daily advance rates in complex geology, in mixed face, in fractured rocks, in transition zones etc. are in big concern (Namli et al. 2013, 2014). The first experiences in Istanbul with a gripper type TBM was a nightmare, roof collapses caused big delays in tunnel excavation (Bilgin 1993). A typical example to EPB-TBM was Kadikoy-Kozyatagi tunnel, changing TBM from opened mode to closed mode with few modifications on the cutterhead resulted a tremendous increase in the daily advance rates (Bilgin et al. 2009). The data collected from several tunnelling projects served a basis to create a model to predict daily advance rates of EPB TBMs. Within the frame of a research program the validity of the model was tested in Uskudar-Umraniye–Cekmekoy-Sancaktepe metro project and very recently in Mecidiyekoy-Mahmutbey project."

Jan 1, 2016

By G. W. McCaa

Plans for a large industrial development in the Upper Ohio Valley between Moundsville and New Martinsville, West Virginia, were announced in the Fall of 1955. This development consisted of a large aluminum plant to be .built by Olin-Mathieson; a 675,000 KW power plant to be constructed by the American Electric Power Service; and a large coal mine adjacent to the power plant to be developed by the Hanna Coal Company Division of Consolidation Coal Company. The Ireland Mine was designed to efficiently supply fuel for the power plant, and this was the first consideration in the location of facilities, design, and development of plant and the selection of the equipment. The first problem was to find a suitable area for the surface facilities. A level bottom area south of the power plant was reserved for future industrial plants and this area was also blocked off from the coal reserves by an old abandoned and flooded mine. The coal storage facilities of the power plant were on the north side of the plant and it was decided to locate the coal mine preparation plant on-the shoulder of a hill above the power plant. This location required the excavation of 70,000 yards of rock but permitted the driving of a belt slope from the plant at an angle so that the haulage roads underground would miss the abandoned Cresap Mine. This location also permitted the plant to be located at an elevation so that the conveyors leaving the plant were horizontal and had sufficient clearance above the highway and railroad tracks. The other surface facilities consisting of air shafts, supply slope, supply yard, office, bathhouse, shop and warehouse were located in the valley some distance north of the preparation plant. This location placed these facilities one mile nearer to the working area. Plans for design and development of the mine were started in November 1955; grading and clearing of surface area was started in January 1956; the air shafts and slopes were started in the Spring and Summer of 1956; and the first coal was produced from the supply slope in October 1956. The preparation plant was put in operation in March 1958, and by July 1959 was producing 8,000 tons per day.

Jan 1, 1959

By Michael M. Kimberley

Gold is sufficiently valuable that concentrations as small as 1 p.p.m. may support low-cost mining. Mindful of this, Sunoco Energy Development Company (Sunedco) obtained fire-assay analyses on some sulfide-rich sandstone encountered during routine drilling. Initial fire-assay values from independent laboratories indicated some significant gold values and independent analysis by atomic-absorption spectroscopy also indicated detectable gold at economically interesting concentrations. Sunoco geologists realized the potential for spurious results inherent in both fire assaying and atomic-absorption spectroscopy. Fire assaying that relies on gold measurement by weight requires perfect separation of gold from all other elements, Imperfect separation may artificially enhance apparent gold concentrations. Atomic-absorption-spectroscopy (AAS) measurements are potentially subject to interferences from other elements. For example, Beamish and Van Loon (1977, p.4) report AAS measurements of 4 p.p.m. Au to be characteristic of completely barren soil samples when samples are prepared by standard dissolution in HC1 to form solutions of about 10,000 p.p.m. total cations (mostly Na, Ca, Mg, Al, and Fe) .

Jan 1, 1981

By Kirsten Corin, Belinda McFadzean, Cyril O’Connor, Jenny Wiese

The Bushveld Complex of South Africa contains almost 90% of the world’s reserves of platinum group minerals (PGMs). In the flotation of PGMs, there are significant challenges arising from the need to treat ever-decreasing grades of the relevant ore deposits. The major challenge in the flotation of these ore bodies is the control and management of the gangue minerals, particularly silicates such as orthopyroxene, plagioclase feldspar, and pyroxene which are often rimmed with talc which makes them naturally floatable. It has been shown that various polysaccharide depressants such as CMC and guar have different properties in terms of depressing the gangue minerals. Since the PGMs are often associated with sulphides, copper sulphate is widely used as an activator in PGM flotation but can inadvertently activate the gangue minerals as well as reduce the recovery of PtTe2 which accounts for up to 40% of the Pt in the Platreef ore body. Depressants also reduce the mass of solids reporting to the froth and can thus destabilise the froth. This effect on the froth can be mitigated by using higher frother dosages or water of higher ionic strength. Reducing chromite recovery is of critical importance since high levels may negatively affect the downstream smelting process. Chromite recoveries can however be reduced through the application of gravity separation or reducing entrainment through reduced water recovery. In summary, due care needs to be taken to carry out site test work to develop an optimum ratio of collector, frother, activator, and depressant to ensure that the highest grades and recoveries of the PGEs are obtained while reducing depressant dosage as much as possible.

By H. Cho

There is an indication that high-pressure roller milling promotes selective liberation due to preferential breakage along the mineral boundaries. A study was undertaken to compare the degree of liberation obtained by high-pressure roller milling with that of conventional ball milling. Coals with different HGI's were ground in a high-pressure roller mill and a ball mill to produce products with similar size distributions. The products were then subjected to float-sink separations to determine the degree of liberation. Also, the relative cleanabilities were compared by separating the ground products by froth flotation. The results from this study are presented in the paper.

Jan 1, 1994

By W. Zhang

"The adsorption of collector on chalcocite has been studied in situ in aqueous solutions by applying an atomic force microscopy (AFM). The AFM images show that xanthate, such as potassium ethyl xanthate (KEX) and potassium amyl xanthate (PAX), adsorbs strongly on chalcocite mainly in the form of insoluble metal xanthate, which binds strongly with the mineral surface without being removed by flushing with ethanol alcohol. The result clearly shows that the adsorption of xanthate on chalcocite is totally different from its adsorption on chalcopyrite, during which oily dixanthogen is the main adsorption product on chalcopyrite surface. AFM images also showed that increasing solution pH to 10 doesn’t prevent the adsorption of xanthate on chalcocite much and the result confirms with the fact that chalcocite floats well in a wide pH range up to 12 with xanthate being used as a collector. INTRODUCTION In flotation, the adsorption of collector on mineral surface is vital for a successful flotation process to achieve a satisfying metal recovery. Historically, many works have been carried out to clarify the adsorption mechanism of collectors on sulfides. (Gaudin and Schuhmann, 1936, Poling and Leja, 1963; Allison et al., 1972, Fuerstenau, 1982; Leja, 1982; Woods, 1984) The adsorption of xanthate on chalcocite surface in aqueous solution also attracted the interest of many researches. Gaudin and his colleagues (Gaudin et al., 1934; Gaudin and Schuhmann, 1936) studied the solubility of potassium ethyl xanthate and its reaction products in organic solvents and firstly proposed there was initially chemisorbed xanthate (X-) on chalcocite surface followed by insoluble cuprous xanthate (CuX). Allison et al. (1972) studied the reaction products of various sulfide minerals with xanthate solutions and reported that the measured rest potential of chalcocite in 6.25×10-4 M KEX solution at pH 7 was +60 mV and the reaction product of PAX on chalcocite was cuprous xanthate. Mielczarski and Suoninen (1984a, 1984b) applied the XPS and studied the adsorption of potassium ethyl xanthate on cuprous sulfide. It was reported that there was a relatively rapid formation of a well-oriented monolayer of xanthate ions followed by a slow growth of disordered cuprous xanthate molecules on top of this layer. Richardson et al. (1984) carried out an electrochemical study of chalcocite flotation with the addition of ethyl xanthate. It was proposed that cuprous xanthate and possibly cupric xanthate were adsorbed hydrophobic species on chalcocite surface due to the exchange and charge transfer oxidation reactions. Leppinen et al. (1989) applied an in-situ FTIR study of ethyl xanthate adsorption on sulfide minerals under conditions of controlled potential and they concluded that, for chalcocite, there were three different potential regions of xanthate adsorption, including chemisorption, copper ethyl xanthate formation on the surface and multilayer formation."

Jan 1, 2015

By S. Dawson

The Republic of South Africa has become a major producer of opencast coal in recent years. Opencast production commenced in 1970 and by 1977 some 10 million run of mine tonnes were being produced annually, Since then surface mine activity has increased to more than 60 million tonnes which represents approximately one third of the total annual South African? coal production. Whilst a substantial portion of this production is exported, the majority is used in the domestic market, The largest consumer, being the South?\ African Electricity Commission (Eskom), produces most of South Africa's electricity using coal fired power stations,

Jan 1, 1990

By Byron R. Berger

Epithermal Ag-Au deposits form at low to moderate temperatures in near-surface environments. Historically, these deposits have been the source of high-grade ores. Increases in the market prices for gold and silver make lower-grade ores economically viable when available in large tonnages. Both the high-grade and bulk-tonnage ores are a consequence of the same processes, and general models of epithermal systems can be useful in the search for new precious-metal resources. A detailed study of deposits at Round Mountain, Nevada; Balei, Russia; Creede, Colorado; Guanajuato, Mexico; and Chanarcillo, Chile, indicates that the hydrodynamics of the fluid systems as determined by fracture geometries, the permeability, and composition of the host rocks are the key factors in the creation of both high-grade and bulk-tonnage epithermal deposits. End-member models that explain the range of observed deposit characteristics are: (1) the hot-springs deposition model; (2) the stacked-cell convection model (where mineral deposition occurs laterally along the interface of two partially separated fluid reservoirs); and, (3) the closed-cell convection model (where deposition occurs in vertical zones due to the relatively unimpeded vertical flow of hydrothermal fluids). Boiling and fluid mixing appear to be agents of precious-metal deposition with the self-sealing of the hydrothermal system being an important adjunct to boiling. Imaginative application of model concepts in exploration has led and can lead to the discovery of new high-grade and/or bulk-tonnage precious-metal deposits.

Jan 1, 1982

It is widely accepted that particles stabilize flotation froths and that stable froths result in improved flotation performance. Predicting the effect of particle addition on froth stability is, however, challenging. Furthermore, there is currently no technique that allows the prediction of the effect of different flotation reagents on froth stability, without carrying out froth stability experiments.

By R. S. Shoemaker

Expanded markets for copper in the past few years and a consequent search for new ore bodies have revitalized the widely known but seldom applied method of producing copper called heap leaching. This term should be differentiated from dump leaching in that the latter is applied to dumps of mixed oxide and sulfide ores (although either may predominate) that have been too low grade to beneficiate and have, therefore, been stripped off the higher grade underlying sulfide ores. Heap leaching is defined here as the process applied to oxide ores which have been mined solely for the purpose of leaching. In this case, all costs of mining the ore become a part (and a substantial one, as will be shown) of the cost of the copper produced, whereas in dump leaching the mining cost has already been accounted for as a stripping cost for the sulfide ore. Of course, with newly opened ore bodies, stripping costs may be divided through accounting procedures, between the copper produced by the mill and that obtained by leaching, but in general this type of operation must be economic on the basis of the sulfide ore alone. Heap leaching, as a beneficiation method, is unique in that it is the only process used for the recovery of a metal in which the time involved from mining the ore to metal production is measured in months instead of hours or at the most, days, Then too, after the ore body has been depleted and mining has ceased, metal production will continue for some substantial period of time. Heap leaching is also unique because unlike any other method of beneficiation, metal recovery cannot be accurately forecast ahead of time and recovery will never approach that of a conventionally milled sulfide ore or even that of a vat leached oxide ore. Counter-balancing this drawback, however, is the relatively low capital expenditure necessary to put a heap leaching operation into production and the consequence that smaller ore bodies which would not support the higher capital cost involved in a vat leaching plant can be made into producers. Stated more simply, in heap leaching the operator accepts low recovery in exchange for low capital costs and the break even point, that is, where the operator should go to vat leaching with its higher recovery and higher capital costs, is a matter of economics and also, to a great extent, a matter for the nature of the ore to decide. For instance, an ore that will vat leach in 7 to 10 days using 7 pounds of sulfuric acid per pound of copper produced might use double or triple that amount of acid during the months that are required for heap leaching.

Jan 1, 1968

By Robert W. Row

The run-of-mine coals in the U.S. being fed to coal cleaning plants have become increasingly finer due to the adoption of modern, mechanized mining methods, and economics are dictating that finer fractions, as well as the coarser fractions, be cleaned. Traditional dewatering methods (vacuum disc filters and centrifuges) are proving inadequate for preparing fine refuse for disposal or fine coal product for downstream handling. The Electric Power Research Institute has been supporting research into the nature and limitations of mechanical dewatering, and novel ways of improving it. The efficiency of various silicone-based chemicals at aiding dewatering was investigated, and it was shown that the final moisture content of hydrophilic coals after vacuum Filtration could be reduced by 1 to 5% with up to 40% increase in filtration rate by addition of one of several of these silicones. EPRI also has an on-going program at its Coal Cleaning Test Facility to investigate the performance of the Larox pressure filter in comparison with that of the disc filter and solid bowl centrifuge. While improvements to the dewatering performance currently being obtained in existing operating plants by such means are achieveable, a fundamental study has shown that, regardless of changes in operating conditions, there may be a limit to the lowest cake moisture content attainable by mechanical dewatering of a given sample of coal fines. Determination of this limit for a specific coal would be useful in designing facilities to dry and handle it.

Jan 1, 1984

By Richard Newcomb, Michael Rieber, William A. Vogely

INTRODUCTION The solid fossil and nuclear fuels, but especially uranium, are given prominent, indeed leading, roles by energy experts in most long range estimates of world energy futures. Optimistic forecasts are inspired partly by the disproportionately large solid fuels resource base compared to present rates of consumption or to oil and gas resources, and partly by the vision of inexpensive high technology applications. Such a view overlooks the fact that while resource- use disparities and new technologies give allure to the promise of the solid fuels, they do not guarantee cheap solutions to the basic problems of solid fuel uses: viz., their relatively difficult conditions for efficient ignition and control, including the management of environmentally acceptable residuals disposal. Contrary to the varied versions of this optimistic hypothesis, this paper shows that a great many persistent economic and technical problems interfere with such a simple inference. These act as constraints which qualify or dispute much of the national energy policy based on existing modeling of solid fuel requirements and optimistic engineering evaluations. The assumptions and techniques of such exercises are sometimes at fault. As often as not, however, the distortions created in open market fuel com- petition due to misdirected national energy policies themselves are to blame for misdirected efforts. A number of interesting implications result. Among them are the distinct possibility that the low technology applications will dominate, so that more direct coal and less synfuel or nuclear use will occur; that, accordingly, exhaustion rates for uranium will be low, that the most extensive growth of solid fuel through 2000 will be in conventional pulverized coal cumbustors, and that the traded share of the world coal bum will be much larger than predicted. These trends will place much more pressure on oil and gas prices than forecast by most experts. On the way to these findings the paper demonstrates that solid fuel resource adequacy in situ, balanced against the projections of demands as capacity requirements, mean little as conventionally measured by years to exhaustion or potential supply schedules. Indeed, all stock concepts of demand requirements or of fuel re- sources must be tied to the paths of the unit costs and the deliverable prices of all substitute fuels and systems over time. This requires a dynamic analysis of supply and demand, integrated with geological and engineering constraints, to provide insights into the multiple modes of market and product substitution. Market forces rather than technical promise will determine the allocation of the solid fuels. Moreover, the equilibrium paths of individual fuel prices and market shares are not easily simulated by general or network models, and decision makers will continue to rely on the partial, local comparison of alternatives in their choices of fuel systems at any time. 'The economics of the solid fuels differs from that of other energy sources in important ways relating to their form in use, conversion efficiency, (dis)economies and externalities. Petroleum and gas are in a more convenient form for

Jan 1, 1985

By W. L. Staker

The Bureau of Mines investigated selective extraction of Au and Ag from a low-grade Au ore containing Hg. Gold and silver were extracted from the ore in cyanide slurries, and Hg extraction was suppressed with sodium or calcium sulfide. Maximum Au extraction and minimum Hg extraction were obtained using solutions containing 0.34 lb NaCN/ton of solution. Increasing the cyanide concentration increased Hg extraction without increasing Au extraction. Mercury extraction from the ore was suppressed with 0-5 to 2.9 Pb CaS/lb Kg in the ore. Gold-to-mercury ratios of 100:1 to 400:1 were obtained in the leach solution, and on the activated carbon in a CIP circuit.

Jan 1, 1983

By Alfred A. Roetzer

In several sections of the country new demands are being brought bar cement users. Among these the demand' for truck shipments; and palletized loads present new problems that do not lend themselves to sample solution. In fact these demands have far-reaching effect in the way bagged cement might be marketed. Early solutions of palletized truck loads filled from existing packing and loading facilities have resulted in' slowdown in packing, additional labor and space for palletizing, considerable experimentation in type and construction of pallets, and usually far from optimum truck handling and loading methods.

Jan 1, 1961

By C. W. Armbrust

At FHC Gold Company's Paradise Peak Mine gold and silver are produced. Precious metals recovery rates are very satisfactory along with the recovery and production of a relative high volume of mercury. At Paradise Peak precious metals are recovered via the Merrill-Crowe process and delivered to the refinery area as a mercury-bearing precipitate cake. The recovery of mercury is then obtained through a vacuum retort system. The balance of the material is mixed with fluxes and then melted and cast into dore' bars for shipping. Issues of retort capacity and concerns over efficiency led to research into the retort process itself.

Jan 1, 1990

By Wern-ping N. Chen

Pressure tunnel includes water-supply tunnels and tunnels for hydroelectrical power plants. Their design principles are different from those of water/wastewater/conveyance and transportation tunnels. Though theoretical pressure tunnel design guidelines exist, a comprehensive guide to summarize these guidelines to facilitate the planning and design of a pressure tunnel program is lacking. The purpose of this paper is to fulfill this need. It first provides key pressure tunnel design concepts in hard rock environment; then, it illustrates associated final lining design principles, including the design of un-reinforced concrete lining, steel lining, and reinforced concrete lining. Design diagrams and a flowchart for the reinforced concrete lining design are provided.

Dec 1, 2022

By Wayne Trudel, Lloyd McEvers, Lori Clarke, Eric Saderholm, Charles Lynn Bolin, Leroy Schutz

Newmont mine geologists in Nevada are most proficient when applying technical expertise with multi-departmental teams in three main settings. The first is value creation through near-mine discovery, development and reserve conversion. Since 1986, geologists have created substantial net asset value in developing more than 1.35 kt (43 million oz) into quality Nevada surface and underground gold reserves. The second setting is value realization by supporting mine operations with ore control, selective mining, reconciliation investigations and strategic planning. The investment of technical research on reconciliation investigations led to new concepts and practices that highlighted opportunities for large revenue and reserve gains. In 2002, more than $65 million in projected revenue was added to the Gold Quarry south layback. Kriged mine polygon construction and controlled blast heave at the Lone Tree Mine provided millions of dollars in mining efficiencies. High-quality geologic advice in selective mining at the Twin Creeks Mine helped obtain $4.3 million revenue gains throughout 2002-2003.

Jan 1, 2004

By R. K. Mehta

Stirred ball mill feed used for ultra-fine grinding application requires fine size separation step in order to avoid over-grinding. This paper presents the selectivity curves obtained for oil shale and complex sulfide are using 460 mesh (30 micron) Derrick vibrating screen. Interestingly, the selectivity curves generated from the experimental data were monotonic increasing selectivity for oil shale but not monotonic increasing for sulfide ore. These non-monotonic increasing selectivity curves were similar to the mechanical air separator fishhook selectivity curves described by Luckie and Austin. A 2 stage classification in series model describing the fishhook selectivity curve has been used in proposing the classification mechanism for fine vibrating screens when heterogeneous multicomponent sulfide are undergoes size separation.

Jan 1, 1992