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By P. Coleman, J. C. Kerkering, S. Iverson

A fatal accident may result when a dozer is driven over a hidden void in a coal surge pile and the dozer falls into the void, burying and suffocating the dozer operator. This type of accident was analyzed by researchers from the Spokane Research Laboratory of the National Institute for Occupational Safely and Health using inexpensive fault-tree programs that had been developed, for use on a personal computer. Fault-tree analysis is a systematic safety-analysis tool that proceeds deductively from the occurrence of an accident event to the identification of the root causes of that event. The analysis identified basic and intermediate events that led to the burial of the dozer and graphically depicted the interrelationship between the basic events as well as the intermediate events leading up to the accident. A sensitivity analysis on assigned probabilities showed which events had the greatest influence on dozer burial in a coal surge pile. Operational guidelines and engineering controls are suggested to decrease the probability of a burial event.

Jan 1, 2002

By D. A. Swanson, G. Danziger, G. Savci, C. Barnes

Hydrologic assessments of existing and proposed waste rock stockpiles are typically required for application of operating and closure permits at mine sites. A hydrologic assessment should include an evaluation of climatic data and prediction of the net infiltration rate through the waste rock stockpile surface. In addition, hydrologic factors such as the time required to deplete available moisture storage in the stockpiles and the time required for potential seepage to migrate to the underlying aquifer should also be predicted.

Jan 1, 2000

By J. J. Crowhurst

The modem open pit-heap leach operation by Pegasus Gold Ltd. at Zortman and Landusky in Phillips County, Montana, is a new chapter in the mining of gold in these districts. The discovery of bulk tonnage ore bodies and their development and ultimate production was based on a long history of mining and exploration in that part of Montana. Gold was originally discovered in the Little Rocky Mountains as placer deposits by Pike Landusky and Lou Myers. This discovery in the 1880s was not significant, but Pike Landusky continued prospecting for lode deposits, and he eventually located the Gold Bug and Little Ben, two of the larger Au-Ag producers in the district. Eventually two camps, Landusky and Zortman, grew in the LittleRocky Mountains. By the time Landusky was killed in 1894 by Kid Curry, the district was still a discontinuous small producer. Steady production commenced in 1907 with the organization of the August Gold Mining Co. Eventually high grade ores on specific veins were exhausted by selective underground mining and the district was idle by May 1942. After World War II in the early 1950s. E.A. Scholz tried to continue selective underground mining, but he realized the stockworks surrounding the larger veins constituted bulk tonnage targets. Ultimately in the 1976- 1979 period he organized two exploration efforts, one each for the Landusky and Zortman areas, and brought these into production as the Argo and Pegasus gold mines. By the time of his death, Apr. 8, 1980, both operations were producing gold. Later the two companies were merged as Pegasus Gold Ltd. Upon the death of Scholz, V.F. Hollister continued as the geological consultant, Ed Roper was engaged as general manager, and J. J. Crowhurst was given the responsibility of executive vice president. The discovery of open pittable ores and the application of heap leach technology was important in the development of mining. Both contributed to the low cost operation that continues to this day. The attached article by L.M. Rogers, then chief geologist, and M.S. Enders, his assistant, describes the geology of the deposit. It was presented at the Northwest Mining Association meeting in 1982.

Jan 1, 1990

By Roshan B. Bhappu

In situ mining and extraction is one of the Frontier Technologies that is destined to play an increasingly important role in the recovery of metals and minerals in the future. This premise is based on increasing costs of labor and energy, increasing awareness of environmental considerations and decreasing ore grades in the United States. Up to now, in situ mining has been successfully applied to a few favorable situations for the extraction of some evaporites, copper and uranium. However, because of its unique technical, environmental and economic advantages, this versa tile technology will find broader applications for the recovery of above commodities as well as for others which are currently extracted by hydrometallurgical means. This paper traces the development of in situ mining and extraction; stresses its dependence on interdisciplinary science and engineering; discusses its theoretical, practical and economic aspects; and finally presents potential applications of this Frontier Technology.

Jan 1, 1985

By C. A. Pickles, S. J. Splinter

Silicon oxynitride, Si2N20, has many of the intrinsic properties of a potential high temperature engineering ceramic material. Some of these properties are similar to those of silicon nitride, which has been more intensively studied. However, although silicon nitride ceramics are approaching a state of microstructural refinement for various engineering applications, silicon oxynitride has received little attention. This has been mainly due to a lack of an economical and reproducible method of producing pure crystalline Si2N2O. Several reports exist on the preparation of crystalline Si2N2O from SiO2 and Si3N4, yet very little kinetic data exist. Even less is known about the carbothermic reduction of SiO2 in a nitrogen atmosphere to produce Si2N2O. In this paper, a review of the properties and methods of preparing silicon oxynitride will be presented. In addition, results obtained by reactively sintering SiO2 and Si3N4 will be discussed. The overall reaction is as follows:

Jan 1, 1990

By Fernando Concha, Arturo Barrientos

The flow in a hydrocyclone is divided into a boundary layer around the walls, an exterior inviscid flow and an air core in the center of the equipment. The boundary layer flow over the lateral walls is associated with the short circuit of particles to the underflow, while the boundary layer over the top of the hydrocyclone and the outer part of the vortex finder tube is related to the short circuit of particles to the overflow. Classification takes place in the exterior flow. The model can be validated with pilot or industrial data and simulates the performance of hydrocyclones in a wide range of design and operating variables.

Jan 1, 1992

By I. Iwasaki, H. Dho

The role of sodium silicate in the anionic flotation of a Florida phosphate ore was investigated using laboratory continuous flotation tests, frothabiliry tests and SEM observations. In the absence of sodium silicate, Ca I+ promoted the unwanted activation of quartz by forming calcium bearing precipitates. The addition of sodium silicate enhanced the flotation efficiency through: 1) the removal of impurity minerals and calcium-bearing precipitates from quartz surfaces by dispersion, 2) drier and more persistent froths stabilized by oily droplets containing calcium silicate precipitates, and 3) higher specific flotation rates of phosphate relative to quartz, leading to faster flotation rates and increased selectivity of separation.

Jan 1, 1991

By L. Adler

Determining whether a railroad locomotive will skid under varying conditions is a fairly routine, pervasive problem. However, some of the equations provided are wrong, others are at best murky. All require correction or clarification. Skidding during heavy braking is a crucial safety problem, possibly resulting in loss of control and collision. It can also be an economic detriment, ruining wheels and tracks and, by inhibiting acceleration, causing reduced full-speed times. While skidding is less likely for rubber-tired equipment, a comparable problem exists for tractor-trailers operating on poor surfaces. The primary reference is to the SME Mining Engineering Handbook (pp. 14-11, Eqs. 7 and 8), which is taken as authoritative and normative (Brantner, 1973). Fundamentally, the physical weight of the locomotive can never be negative (-). However, based on this reference it can be negative on adverse grades, during braking (Eq. 7), and on favorable grades, whether accelerating or braking (Eq. 8). Additionally, it should be noted that the term rW should be Rw. To avoid having the locomotive weight turn out negative, "absolute value" brackets must enclose the right-hand expression of both equations. Also, the weight of locomotive can be greater than the right-hand side value introducing the common "greater than or equal to" symbol (>_). While these alterations are easy to make, the use of the algebraic sign associated with each term is still confusing, as

Jan 1, 1991

By J. G. Pippenger

The Coteau Properties Company's Freedom Mine is a surface lignite mining operation located near Beulah, North Dakota. Coteau, a wholly owned subsidiary of The North American Coal Corporation, produces more than 13.5 million tonnes per year, ranking it among the largest mines in North America. In 1993, Coteau ranked seventh in terms of annual coal sales, becoming the largest mine outside the Powder River Basin of northeastern Wyoming. However, for the Freedom Mine to stand among these Powder River heavyweights, Coteau over-came several obstacles, including a coal seam with three quarters the heating value and overburden to coal ratios three times higher than the Powder River mines. Coteau's ability to compete has been built around a program of continuous productivity improvement, cost efficiency, and innovation. This report highlights a few of the major improvements implemented in recent years.

Jan 1, 1995

By E. A. Devuyst, G. H. Robbins

The Inco process can be retrofitted into a typical heap operation with minimum capital. Capital cost for a mid to large size heap would be less than 1 cent/ton. Operating costs are typically in the order of 8 cents/ton. Ammonium bisulphite is the preferred reagent. The process provides the equivalent of fresh water r?1s­ing and thus minimizes the time of the _nnse program. A typical heap (the Snow Caps Mine, California) was rinsed completely

Jan 1, 1996

By C. R. Stephan, N. B. Greninger, W. A. Slivensky

The U.S. Bureau of Mines and the U.S. Mine Safety and Health Administration (MSHA) are participating jointly in a research program to evaluate strength characteristics and air-leakage resistance of various proposed seal designs for use in underground coal mines. Over 20 full-scale seals were constructed in the Bureau's experimental mine at the Lake Lynn Laboratory, air-leakage tested, then subjected to pressure pulses of 0.14 MPa or greater. A discussion on the experimental procedure, construction techniques, and the explosion and air-leakage test results is presented. Four types of construction material were used during this seal testing program: solid-concrete-blocks, low-density foam blocks, cementitious foam, and wood blocks. Only one of the solid-concrete block designs using a mortared thick wall survived the explosion and air-leakage tests. Most of the low-density foam block and cementitious foam seal designs were judged to meet the requirements to be considered a coal mine seal. One of the wood block convergence seal designs failed explosion testing. Based, in part, on these research findings, several alternative seal design constructions using low-density foam blocks, cementitious foam, or wood have been approved by MSHA for use in coal mines.

Jan 1, 1993

The importance of factoring mining dilution into the estimation of ore reserves in an open pit mine is discussed. An example that relates the issue of mining dilution to the size of the smallest volumes that can be mined selectively is given. The relationship between the size of the selective mining units (SMUs) and the variance of their average grade is presented. The concept of variance reduction and its use in factoring mining dilution into geostatistical ore reserve estimation is described. An approach to estimate a variance reduction factor by way of conditional simulation is introduced.

Jan 1, 1998

By E. J. Duggan

In the course of the grinding experiments conducted at Climax over the past twenty years one interesting phenomenon was discovered. This was that balls made of certain types of steel grind more ore than some others. The most significant variation was found in the results secured with a hard alloyed forged bail compared with the forged carbon ball supplied by most ball manufacturers These findings were confirmed in many repeated controlled tests. The value of these tests depends on the methods used, the facilities available and the care with which the investigations were conducted. These are described in the following. This testing has largely been done in eight 91 x 81 low discharge ball mills in closed circuit with 7811 duplex screw classifiers. The mills run at 20 RPM on a feed approximately minus 3/8 inch. The ore is ground through 28 - 35 mesh in one stage. Each mill and auxiliary classifier is in a separate, parallel grinding and flotation section The, ore to each: section is the same in every particular and is fed to each mill bin from a common conveyor tripper. The ore from the bin to the ball mill is weighed on a conveyor scale. The power input to each mill motor is determined with a watt hour meter which measures the power to the mill motor only. Both the scales and meters are checked periodically by standard methods and have been found to give consistent readings. Automatic samplers are employed on each section to obtain accurate measurement of the size reduction. A size analysis of the classifier overflow is made each shift and a composite size analysis is obtained from a weighted average of the various shift analyses. The mills are driven by 450 horsepower synchronous motors so that there is no speed variation and shell liner age is kept as nearly the same as possible in mills under test. The same set of operators is assigned to a mill under test as to the control mill. In all other particulars such as ball load, mill density, liner design, etc., the mills are operated in precisely the same manner. This is an ideal arrangement for plant testing. From observations of ball mill performance over the past twenty years, it is the opinion of the operating staff that variations of as little as one to two percent in mill capacities may be determined if sufficient operating hours are devoted, to a test. Relations between mill capacities, fineness of grinds and power consumptions have been established with a high degree of accuracy. In Table I are given the figures for one test. These show that while the grind with the hard ball was slightly coarser, the tons ground per hour was 5.4 percent greater with the soft ball, and 6.1 percent greater on the basis of minus 100 mesh produced. The power consumed per ton with the hard ball was 4.4 percent greater on a tons per hour basis. The soft ball was inferior in wearing qualities and steel consumption per ton of ore was 24 percent greater with it. In this test the mills were charged with the two different balls for a period of three months to allow the ball loads to come to equilibrium. In Table II are given the specifications of the two balls. The difference in grinding rates may be accounted for by the nature of the ball surfaces. The surfaces of the soft balls after being worn a while are rougher to the touch. Enlarged photographs of the worn-in surfaces of hard and soft balls are shown in Figure I. These show the presence of scratches or skid marks on the hard ball surface which indicates less nipping effect. The Climax ore pulp has a pH of 6.0 and is in a dispersed state. The viscosity is low compared with most ores especially those that are conditioned with lime. This would lower the tendency of the pulp to adhere to the balls with a lower grinding efficiency as a result. It was also thought that the relative rates of wear from surface to center might affect the make-up of an equilibrium ball charge. This probably has little effect on capacity as shown by the size analyses of the two ball charges in Table III. This hypothesis was subsequently investigated by the use of rationed charges. The rationed charge did not overcome the advantage in

Jan 1, 1958

By J. H. McNamara

A process has been developed for the successful hydrometallurgical extraction of copper from sulfide ores. The extracted copper in the form of a salt is converted by reduction to copper metal. Purification of the metal is described which includes a description of the casting of ETP quality copper wire bars.

Jan 1, 1978

By Thomas G. Hayes

Track-type tractors remain one of the most cost-efficient stripping tools available to coal miners. Whether they are "sweetening up" a dragline operation with prebenching or serving as the primary tool, dozers are important in driving down mining costs. This article reviews the application zone of track-type dozers. It also provides suggestions for site setup, equipping tractors and machine operation. In recent years, the track-type tractor has become more of a production tool in mining. With the advent of bigger machines, bulldozers have become a typical component in mining operations, removing overburden down to the top seam of coal. Large tractors can also be teamed up with draglines and other systems to maximize the effectiveness of the mining system. Bulldozers remain the tool of choice for topsoil removal, spoil reclamation or any application that demands low ground pressure, or short distance. The introduction of the 523-kW (700-hp) track-type tractor to the mining industry has made the bulldozer a low-cost-per-ton means of removing overburden. The large tractors offer enough productive capability to be considered prime stripping tools. And they can lower mining costs by complementing other mining systems (dragline, cast blasting and loader/truck). Four criteria determine whether a track-type tractor is the right machine for a particular application: ? Production requirements - dozer may fit job requirements better than a second dragline. [ ] ? Product support - availability of parts, service and technical expertise. ? Labor situation - how much of the cost per ton goes to the operator. ? Resale opportunity - recover a percentage of capital cost. Mining efficiency is economically controlling the cost of any system. Most operations rate the most economical means of moving material as cast blasting, dragline and the track-type tractor. All three of these systems share one common value: They are all sensitive to distance. Regardless of the application, all mining systems have an economic range. Exceeding this distance will affect cost and productivity.

Jan 1, 1997

By A. A. Peshkov, N. A. Matsko, K. N. Trubetskoy

It is possible to divide the general objectives of a company into two components: maximum expected profits and viability over time. These components are designed to maximize the companies value over time. The evaluation of a project includes both a discounted cash flow (DCF) analysis and a risk analysis. The DCF analysis determines whether the project should be accepted or rejected, and the risk analysis helps to forecast possible deviations from the original estimates. However, the results of both methods do not allow for a quantitative comparison between the main objectives of the venture, and they do not resolve the issue of whether it is advisable to sacrifice immediate profits for future profits. This paper attempts to resolve this issue. The present research was carried out on mining projects with different waste-extraction schedules. Calculations were made using the US Bureau of Mines' usage-of-costs model. Russian experience in open-pit mining is reflected in this paper.

Jan 1, 1996

By Jean-Luc Cornet

Advances in conveyor technology over the past decade have enabled the design and erection of very long overland belt conveyors. Such conveyors usually require head and tail drives to lower the belt tension and belt strength required. This paper provides an overview of the problems encountered in controlling the head and tail drives on such conveyors and some of the solutions developed by CDI for several such projects.

Jan 1, 2002

By M. J. Shulman

The exploration geologist is frequently confronted with the problem of allocating his resources, i.e., exploration effort, among various areas. Although geologic, financial, and logistic considerations influence the allocations, no objective criterion is usually given that determines the optimal allocation. Maximizing the expected gain in information, subject to the constraint of a limited exploration budget, is used as the objective criterion to allocate airborne reconnaissance effort. The information function, I(x), quantifies the expected gain in information, where x is the scale of exploration. To calculate the information function, the following probabilities are required: the probability that an area contains a deposit; the probability that an anomaly is produced by the target; and the probability that an anomaly is produced by a barren area (false signal). Alternatively, the barren areas can be replaced by other targets. To illustrate the allocation method, the optimal number of line kilometers, i.e., the optimal line spacing per area, is determined for an aeromagnetic survey for iron in Egypt.

Jan 1, 1987

By Ron L. Schmiermund

The Ferris-Haggarty underground mine was abandoned circa 1910, and portal discharge has since resulted in degradation of a trout fishery in the receiving waters of Haggarty Creek. Although tunnel discharge varies dramatically in volume throughout the year due to infiltration of snowmelt, compositionally it is a nearly constant low-TDS, pH-neutral, low-sulfate, copper-silicate dominated water. Between infiltration events, components of ARD accumulate in unsaturated, oxygenated environments within upper workings and are delivered to the main haulage level by the subsequent annual snowmelt flush. Mixing with non-ARD mine waters results in neutralization, dilution, and precipitation of amorphous copper carbonate and silicate phases. These mechanisms, combined with variations in the water balance, control the composition of the portal discharge. Understanding the chemical and hydrologic control mechanisms was critical to the design of a passive treatment system to decrease effluent copper concentrations.

Jan 1, 2000

By Byron Belew, Juris R. Harlamovs, D. B. Dreisinger, John L. Watson, G. A. Kordosky, Thomas O. O’Keefe

Unwanted impurities, present in raw materials, are often coextracted along with desired constituents during leaching. Due to its abundance and ease of extraction, the presence of ferric iron in leach solutions, solvent extraction circuits, and subsequently in electrowinning circuits, has always been a problem. In the case of zinc hydrometallurgical processing, iron is frequently an impurity in leach solutions. Purification of such solutions by solvent extraction, using di (2-ethylhexyl) phosphoric acid (D2EHPA) in a kerosene diluent, results in ferric ions being readily extracted along with zinc into the organic phase. Ferric iron has proven difficult to strip from the organic phase, but it is known that ferrous iron may be easily stripped from D2EHPA, and hence a process to effect reduction of iron present in the organic would have great potential. This research investigated a process to directly reduce ferric to ferrous iron in the organic phase, and to strip the ferrous iron using a dilute acid solution. The process utilized metallic zinc as the reductant and a low concentration sulfuric acid stripping solution. The results of the laboratory tests illustrated that iron could be readily removed from the organic phase by simultaneous direct reduction and acid stripping. The reductive stripping process was subsequently utilized in industry at the laboratory and pilot plant levels. The results of the industrial tests were encouraging and demonstrated the potential of this novel concept.

Jan 1, 1993