Search Documents

By B. T. Field

Pyroprocessing systems range from low temperature dryers to high temperature reactors. The materials and process requirements cover a broad spectrum. It is not the intent of this paper to do a detailed examination of individual processes and equipment, since that can be found in a multitude of other sources; rather it is the intent of this paper to examine the key process variables and offer empirical guidelines to assist in a user?s overall evaluation.

Jan 1, 1998

By Y. J. Wang

Optimal sizing of a ventilation shaft is a classical subject in mine ventilation economics.. The shaft size is optimized by minimizing the sum of shaft-construction and ventilation-power costs, or owning and operating costs. The length and air quantity of the shaft are held constant, and the location of the shaft, affecting its depth, and construction and ventilation power costs, is not considered (Hartman, 1961; Lambrechts, 1974; Wang et al., 1978). This paper proposes an approach by which the location and size for a new pair of shafts (intake and return shafts) are optimized for a coal-mine ventilation network. Specifically, the problem is to determine the location and size for a new pair of shafts, and the distribution of air between the new and old shafts so that the combined cost of shaft construction and ventilation power is minimized. The shaft length or depth corresponds to the height of overburden at any shaft location. To simplify the problem, the shaft locations will be limited to the line along the main or submain entries, and the connection entries at the shaft bottom neglected. In order to calculate the ventilation-power cost, the air power of the system should be determined. This in turn requires the calculations of the air quantity and pressure of each fan in the network, satisfying Kirchhoff's laws and Atkinson equation. After obtaining the air power, the cost calculation is straightforward. In the following, we shall assume that the resistances of all airways, and the quantity for each mining section, which is controlled by adjusting the air regulator, are all known. The resistances for the shafts are determined from the estimated friction factors, and shaft dimensions and lengths. Furthermore, it will be assumed that the fans can be selected to meet the duties called for by any network solutions.

Jan 1, 1982

By V. Scovazzo

Cost-effective underground mine configurations have been designed in highly fractured rock masses where the stone possesses a high material strength. A limestone mine in the eastern United States is used to demonstrate procedures for the geotechnical design of one such operation. The mine discussed is located in both limbs and the axis of a recumbent fold that fractured the rock mass. In a highly fractured rock mass, where the host rock has high strength, a design can be developed to alleviate intact rock failure. This is possible because in most cases as the stress levels needed for intact failures are approached, the stresses are quickly dissipated due to movement along discontinuities, which represent planes of weakness. As a result most underground failures in highly fractured rock are due to sliding or toppling. Even when intact rock fails in a highly fractured rock mass, it is the movement along an existing joint or other weakness plane that often initiates or causes this failure. It is therefore important to obtain the characteristics of weakness planes that are the discontinuities within the mass. The required information on weakness planes, geology, and strength of materials is discussed and recommendations for obtaining this information are presented. A discussion is provided on failure modes and the use of developed information for their evaluation. The impact on geotechnical design is demonstrated through pillar sizing procedures; however, this approach can also be applied to mine roof and pillar foundations.

Jan 1, 2004

By R. K. Steinhorst

Multivariate cluster analysis, MANOVA, canonical analysis, and discriminant analysis of hydrochemistry data were used to investigate the directions of ground water movement in basalts in the vicinity of the Hanford Reservation, Washington. The statistical analyses indicate that the hydrochemistry of the ground waters in these basalt formations is distinctly different on each side of the Columbia River. This suggests that the river is a ground water divide or that the river is roughly coincident with a hydrogeologic barrier boundary. The statistical procedures used in this study constitute a quantitative means for differentiating ground waters according to hydrochemistry.

Jan 1, 1990

By John E. Roberts

People are not a novelty. But the phenomenal numbers thereof, who have approached, settled, and been born in California in the past twenty-five years, are such a problem as to be a novelty in the broadest sense of the word. California, with less than 7,000,000 people in 1940, and over 19,000,000 in 1966. In 5 1/2 years, (1960-65) the southerly 14 counties of California, which together comprise one-half the land area of our state, had an increase in population greater than Colorado, or Arkansas, or Oregon, or any one of 19 other states.

Jan 1, 1967

By Alan A. Campoli, Michael D. Zuber, Frank E. McCall, Gerald L. Finfinger

Injecting water under pressure to wet the coalbed in advance of mining reduces mining-generated respirable dust. Owing to economic and geological barriers, water infusion for longwall dust control in the United States is currently limited to the Pocahontas No. 3 Coalbed in Virginia. Water is pumped into the coalbed through underground boreholes drilled horizontally from the headgate toward the tailgate side of retreat longwall panels. This paper theorizes that the barriers to widespread utilization of water infusion for longwall dust control could be overcome by long-duration, low-pressure water infusion through vertical gob gas boreholes. Currently, 43% of the 72 longwall mines in the United States employ vertical gob gas boreholes. Computer coalbed reservoir simulation suggests that one vertical surface borehole could infuse the same longwall panel area as four horizontal boreholes in the current water infusion system for longwall dust control in the Pocahontas No. 3 Coalbed.

Jan 1, 1995

By Robert J. Timko, Lincoln Derick

This work is a follow-up to previous research that attempted to predict the location of spontaneous heating episodes in underground coal mine pillars. The objective of the original work was to see if the data obtained by commonly used detection methods could accurately predict spontaneous combustion episodes in coal pillars. Data accumulation during the study was enhanced when a spontaneously generated fire occurred within one of the pillars being examined. The fire provided researchers with realistic data that could be used to determine if fire prediction was possible. Results from the initial study found that the atmospheric status equations that were used provided little advance notice that combustion would occur where it did. This study reevaluated the accumulated data by applying it to recently developed equations and compared these results with previously obtained information to determine if a combination of these techniques could more effectively predict impending combustion.

Jan 1, 1995

By A. G. Nitschke, I. Ossenbühl, W. Dolsak, J. Dase

"The authors have successfully developed an innovative rehabilitation concept, which meets actual technical standards and minimizes the impact on the operation of a key conveyor tunnel. A flexible and stepwise ground support rehabilitation program utilized a combination of yielding steel arch sections with grout filled fabric hoses, which represents a fast and safe backfilling support system. The system was developed and successfully installed at Bingham Canyon Mine, the world’s largest open pit copper mine, which also includes numerous underground structures. The mine is owned and operated by Kennecott Utah Copper (RTKC) a fully owned subsidiary of Rio Tinto. The system was implemented at a conveyance tunnel, which was originally designed as a railroad tunnel, but was re-commissioned and is currently used as a conveyor belt tunnel to transport ore from the open pit to processing facilities outside the mine. The existing structure showed signs of overstressing due to movements in the surrounding rock mass, which had to be addressed with a yielding support system in order to provide safe access into the tunnel. However, the impact on the conveyor belt operation due to support installation was to be limited to the bare minimum. Keywords: rehabilitation, yielding support, mining, stabilization, and grout filled fabric hose.PROJECT DESCRIPTION The C6 Tunnel is considered a critical asset for the operation of the Bingham Canyon mine as it comprises the standard route for transporting crushed ore from the open pit to the processing facility on a continuous conveyor belt system. The C6 tunnel was originally built as a railroad tunnel. Construction was completed in 1959. The original horse-shoe shaped cross section of the tunnel was 18 feet wide and 24-1/2 feet high [8]. The tunnel length was approximately 18,000 feet. During its service life, the railroad tunnel has undergone several transformations. The length of the tunnel towards the Bingham Canyon pit was shortened over the course of mining operations and the railroad tracks in the tunnel were removed. The invert was partially backfilled (3 feet typical) and a 72 inches belt conveyor was installed. Currently, the C6 Tunnel is nominally only approximately 21 feet high and 15,000 feet long. Ground Support and Rehabilitation Measures prior to 2014 The C6 tunnel was mined mainly with conventional mining methods, using drill & blast as the typical one. However, the weak geological sections, such as those encountered in the Fortuna fault, were excavated by shaping and chipping with machine-held moils [8]."

Jan 1, 2015

By Benjamin C. B. Hsieh

Many processes in the hydrometallurgical and chemical industries require the separation of dissolved material from suspended solids. Counter current decantation (CCD) with thickeners is one of the methods generally used. The process engineer needs a quick and accurate CCD calculation method. Several theoretical 1-12 CCD calculation methods are available in the literature . The simultaneous 1, 2 equation method for a complex circuit as used would take too long to solve the problems. Approximate equation method1 is not accurate and is for simple cases only. A shortcut method developed by Counselman3 contains no mathematical equation, and thus is not suitable for computer programming. Based on Counselman's method, Woody4 derived two simple equations in terms of percent soluble loss for two typical examples. Scandrett5 included a term for mixing in his formulas. This mixing efficiency was defined by Murphree6. Another method which depends on making volume calculations instead of using weights is presented by Mastin8 and Cahalan9. None of these methods is related to dissolution and pre¬cipitation reactions. Chen 10,11 demonstrated his methods for counter current leaching. His results are calculated from the general solution of a derived linear difference equation for constant underflow, and from the solution of a derived non-linear Ricatti difference equation for variable underflow. This paper concerns derivation of a general equation for CCD washing with provisions for adding and withdrawing the streams, and for leaching (dissolution) or precipitation reactions. These equations take several forms depending on the input information available. A set of simplified equations for continuous counter current washing and leaching is derived for determining:

Jan 1, 1972

By Thomas Novak, Philip Johnson, Richard L. Sanford, Lloyd A. Morley

Macintosh use in mine-planning applications lags DOS machines since many users have made significant investments in hardware and training for other environments. Macintosh use is becoming more pronounced in many other industries, and com soft-ware is of at least the quality of that available for DOS machines and many workstations. This paper describes attributes of the Macintosh computer family as related to many mine-planning problems and solutions including software, memory considerations, workstations, DOS compatibility, and networking.

Jan 1, 1993

By Ian Sheppard, John J. Chen

This paper describes the development of the underground mining methods employed for narrow silver-lead-zinc orebodies at the Isa Lead Mine. Cut-and-fill methods were the chief underground mining methods for the narrow orebodies at the mine over 35 years ago. Benching methods were introduced approximately two decades later, and quickly replacing the cut-and-fill methods. The cut-and-fill methods and the benching methods are briefly reviewed in the paper. The benching methods and technologies have been continually evolving and one of the recent achievements is a multi-lift benching method. The multi-lift benching method is described in detail.

Jan 1, 2001

By Ross Glanville

The Optimum Production Rate (OPR) is one of the most important parameters in the evaluation of a mineral deposit. The OPR cam also be expressed as the Optimum Mime Life (OML) in years since the expected mime life is determined by dividing the OPR per year into the estimated ore reserves. Unfortunately, very little time and effort has been directed towards the determination of the OPR. Instead, "rules of thumb" are often applied to select a mime life without due consideration of the economic implications of such a selection. A "justification" for a particular production rate is often based on a pre-conceived arbitrary requirement for a mime life of 5, 10, or 15 years, for example. In this paper it is demonstrated that such arbitrary selections for high-grade/low¬-tonnage mines (such as many underground gold/silver deposits) often lead to sub¬optimal results. In fact, am apparently uneconomic deposit at am arbitrary production rate may be economic at the OPR. Consequently, investment opportunities may be overlooked if one analyzes mime' properties based on arbitrary production rates.

Jan 1, 1984

By D. H. Davidson

The basic principal in the ISL process involves the recovery of metal values by moving fluids through rock instead of moving rock. The process combines surface and sub-surface operations, with the economic performance controlled by four major factors; rates of fluid injection and production from wells; the rate of mineral solubilization; the volume of rock swept by the fluid; and the volume of solution processed through the system. This paper discusses various technical and economic parameters affecting these four factors and how they impact project costs.

Jan 1, 1985

By Leonard Sargeant

The Pocahontas Coal Field consists of eight mineable seams of low-volatile coal in southern West Virginia and Virginia. The deeper seams, especially the Pocahontas No. 3 and No.4 Seams, under heavy cover and below drainage are notoriously gassy. Methane in the Pocahontas Field is generally thought of as being confined in the coal itself, rather than in mud slips or clay veins. Furthermore, it is characteristic of Pocahontas coal to retain its gas until the coal is broken and removed from the solid. Because of this inability for gas to escape from unmined coal, entries developed around large blocks are seldom of significant value in bleeding off methane before pillar extraction begins. This is evidenced by the fact that it is not uncommon to find gas liberated during the mining of chain pillars and barriers which have been developed for several years. The Pocahontas Fuel Company develops almost all solid coal by conventional methods with shuttle car haulage. To provide the maximum productive capacity without compromising ventilation and safety requirements, the Company has adopted standards for ventilating 5, 6 and 7-entry sections.

Jan 1, 1960

By E. H. Cho

Pittsburgh #8 coal cleaned by the conventional froth flotation was oxidized in a 2-liter Parr Stirred Top Bench Reactor. The oxidation time was varied up to 5 hours; the temperature, from 150 to 225°C, the oxygen pressure, from 15 to 500 psi; and coal dosage, from 15 to 60 grams in 600 ml of distilled water. The oxidation of coal was evaluated by measuring total acidic group formed on the coal surface as well as by measuring the adsorption of calcium ion from a solution under standard conditions. It was found that the oxidation increased with increasing oxygen pressure without much leveling-off effect. However, the oxidation of coal increased sharply from 150°C to 175°C and then tended to level off above 175°C. The adsorption of calcium was reached more than 3% on the coal oxidized under favorable conditions. The adsorption of calcium on coal increased sharply with increasing equilibrium pH. The BTU loss was sensitive to oxidation temperature. This study concludes that the optimum oxidation of coal should be conducted at high oxygen pressures around (e.g. 500 psi) 170°C for 3 hours. This study also concludes that the oxidation in an autoclave is far superior to that in a fluidized bed in terms of calcium adsorption, BTU loss and reaction time.

Jan 1, 1994

By R. Henley, S. S. Webster, L. Harris

High resolution airborne magnetic and radiometric data have been shown to optimize exploration for epithermal gold deposits in the vicinity of Charters Towers, northeastern Queensland. The radiometric data allow extrapolation of poorly outcropping geology to provide a cost-effective mapping technique, even at exploration scales (eg. 1:25,000). At a regional scale (eg. 1 : 100,000) the magnetic data reflect the regional tectonics and divide the area into domains for the application of different genetic models. For example: 1. the Ravenswood Batholith is characterized by multiple intrusions dating from Ordovician to Permian age. The polarity of the magnetic anomalies implies an age for the intrusions and indicates a deposit style for exploration. 2. extensional and wrench tectonics along the northern margin of the Drummond Basin are interpreted from the magnetic data and indicate favourable blocks for detailed exploration. Genetic exploration models may be tested in favourable environments by the recognition of geophysical signatures. These signatures reflect structural, lithological and alteration patterns arising from controls on ore deposits and can be applied at regional or detailed scales.

Jan 1, 1989

By M. R. Grundy

The Robinson project is based on the porphyry copper and gold deposits in the Robinson Mining District, near Ely in Eastern Nevada. The district was mined from the late nineteenth century to 1978 by Kennecott Copper Corporation and its predecessors. Operations ceased when falling copper prices in the late 1970's made their outdated mill and smelter complex at McGill uneconomical. In October 1991, Magma Copper Company (Magma) acquired the many claims that cover the known porphyry copper deposits in the district These occupy a disturbed area about nine miles long and three miles wide between the towns of Ely and Ruth. Magma proposes to build a copper / gold mine and concentrator and expand the existing gold leaching facilities. Several pits, previously mined by Kennecott Copper Corporation, will be enlarged; the use of larger, more modem equipment will result in higher productivity and lower operating costs in general. ICF Kaiser Engineers, of Oakland, California, were awarded the con-tract for detailed design of the process facilities, which was essentially complete by the end of 1993. The project at present is awaiting completion of the environmental permitting process; state air and water permits are in hand, and the Bureau of Land Management's (BLM) current schedule indicates that the final obstacles to construction will be cleared by early fall of this year.

Jan 1, 1994

By Evan Adams

The Ireland Mine is located some seven miles South of Moundsville West Virginia, along the bank of the Ohio River. We are mining the Pittsburgh #8 seam. This seam is approximately 60" in thickness, and is immediately overlain by some 10 feet of a conglommerate material. The roof is difficult to control, due to the fact that it frequently is composed of substances not hard enough to be held together with 6-foot roof bolts. In many cases, we must use 10-foot roof bolts, in order to get bolt anchorage in the limestone above the conglommerate. Due to the elasticity of the limestone and its tendency to bend rather than to break, we have been unable to maintain a pillar line. Thus, we have found it necessary to mine by the room and pillar system. Belt haulage is used on room entries to automatic loading stations, thence into 15-ton mine cars, controlled at the loading point by car spotters. The maximum belt length is 2,000 feet. Rail haulage to the slope-bottom dump is by 27- and 50-ton locomotives. The mine produces coal two shifts per day, with 7 production crews on each shift. Mine and machinery maintenance is performed on the Midnight shift. We handle an average of 660 tons per machine shift.

Jan 1, 1964

By Jeffrey D. Swanson, Martin L. Smith

Smelterville Flats in Idaho's Silver Valley has been designated as a Superfund site due to metals contamination resulting from the use of the South Fork of the Coeur d'Alene river as a tailings impoundment earlier in this century. Tailings average in excess of 4% lead and zinc. Selective mining of highly contaminated zones is being studied as one of several possible remediation strategies. The first step towards remediation is the examination of the stratigraphic, geochemical and spatial characteristics of the site. These characteristics are related to appropriate sampling protocols and exploratory sample grid design. Special problems involved in the geostatistical analysis of tailings are emphasized.

Jan 1, 1992

By R. J. Lee

Asbestos analysis is conceptually simple. The objective, in most environmental analyses, is to determine the number of asbestos fibers per unit area or volume in a sample. The sample may be a consumer product, an ambient air sample, or a water sample. This determination is complicated by several factors including sample collection and preparation, counting techniques, and the operational definition of asbestos in use. Three different definitions have been used in the study of environmental samples; these are summarized in Table 1. [ ]

Jan 1, 1979