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By J. B. Mitchell

Comminution methods for base metal and precious metal ores have had considerable attention from mine operators, equipment suppliers and design engineers for many years and much of their work has been well reported. This interest derives from a healthy concern with the costs of comminution, often the largest single cost factor in ore dressing of hard ores. Many imaginative innovations have resulted. One notices a trend toward autogenous and semi-autogenous methods, combined with a trend toward very large equipment. Unfortunately, there has been less obvious cost incentive to experiment with softer ores. This is unfortunate because the consequences of inappropriate comminution methods can have an important effect on overall economics by influencing down stream processing and salability of final products. This paper concerns some of the factors to be considered in the selection of comminution methods for potash ores, and gives some specific examples to illustrate some of the principles involved.

Jan 1, 1969

By Aurel Goodwin

I chose the title "Let's Clear the Air" for this afternoon's presentation because it has two meanings, the literal and the figurative. Most of you know what MSHA is. Most of you know what MSHA does. And, for the most part, most of you know why. What I hope to accomplish today is to "clear the air" around our health standards, to clarify for you how MSHA views its congressional mandate under Title I Section 101(a)(6), (7), and (9) of the Mine Safety and Health Act. Asbestos, silica, radiation, noise, welding fumes, carbon monoxide, lead, hydrogen sulfide, nitrogen dioxide - the list of physical and chemical hazards encountered in the metal and nonmetal mining industry is as diversified as the industry itself, possibly even more so. In addition, miners are often exposed to several of these health hazards simultaneously.

Jan 1, 1980

By Thomas M. Tharp, Mark A. Travers

A new method is presented for precracking three-point bending specimens for fracture toughness testing. A notched specimen of rectangular cross section is placed on a flat loading platen, with paper between specimen and platen. The specimen is loaded from above through a roller placed directly over the crack. The thin, high compliance joint between specimen and platen causes a distributed load on the bottom of the specimen. This results in bending at the cracked section and crack initiation at the notch tip. Since the joint is thin, its stiffness increases rapidly with deflection and crack propagation in the specimen generally remains stable and controllable. Fracture toughness KIC in a sandstone directly overlying the No. V coal was measured to be 0.27 MPa m 1/2. Even for cracks 1 cm long this value of KIC results in substantially lower effective tensile strength (modulus of rupture) in roof beams than is expected from intact rock strength.

Jan 1, 1986

By V. R. Degner

Given: the process tonnage, performance objectives, and plant floor area, the paper will outline the metallurgical and machine hydrodynamic scale-up procedures for translating the lab flotation test results to the design of a full size flotation machine installation, including the machine number, size, and arrangement. Machine selection considerations for rougher, scavenger and cleaner duty, and special considerations relative to specific applications, will be summarized where appropriate. The value of kinetic modeling in quantitative metallurgical (lab to full size machine) scale-up will be reviewed considering a coal installation, and design information for additional applications such as copper, molybdenum, iron, phosphate, and potash will be discussed.

Jan 1, 1986

By J. Engel

The talc deposit in Gemerská Poloma lies 350 to 400 m under the surface; the whole deposit is located at the highest-level drinking-water-source protection zone, therefore, opening in this mining area (a well, a ramp) requires higher investment, operational and water protection costs. The adit, outside the mining area, with a length of 4200 m, rising with a gradient of 3? and a diameter of 10.3 m2, allows free passage/runoff of mining-water through the adit, and guarantees low costs for transporting produced material and equipment. This solution is in total less demanding from both investment and operational point of view.

Jan 1, 2007

By B. K. Parekh

Silicon carbide (SiC) can be produced by heating rice hulls to elevated temperature, The product is a mixture of beta crystalline silicon carbide whiskers, particles and unreacted carbon. The silicon carbide whiskers are 0.5 micron in diameter and 50 to 100 micron in length and have been found useful for reinforcing metal and other composite materials. The carbon can be removed by combustion, but this makes separation of the silicon carbide whiskers from particles difficult and a high grade whisker product cannot be made. However, a clean high grade Sic whiskers product can be obtained from the pre-burned converted rice hulls using physical separation processes that are based on differential wetting. Recovery of Sic whiskers from the pre-burned material was found to exceed 90 percent. A modification of the froth flotation process developed during this study is now being used commercially to separate silicon carbide whiskers and particles and to recover a high grade whisker product.

Jan 1, 1985

By John T. Cumberlidge

The Groveland deposit, in the Upper Peninsula of Michigan, consists of an E -W trending overturned syncline of Middle Precambrian Vulcan iron formation. At Groveland, the Vulcan formation can be divided into four units or facies. The total succession may be more than 550 feet thick, and consists of a basal unit composed of a lean chemical quartzite with traces of magnetite; a non-banded, partly clastic unit characterized by the preponderance of hematite over magnetite; a transition unit of well-banded magnetite-bearing iron formation interbedded with non-banded oolitic hematite; and a well-banded magnetite-quartz silicate unit at the top of the exposed sequence. The present magnetite-hematite ratios of different units within the orebody are considered to be a primary (post-diagenetic) feature of the original sediment. Subsequent regional metamorphism has increased the grain size of the original iron oxide minerals, but did not appreciably alter the oxidation state of the original sediment.

Jan 1, 1964

By David M. Shaw, John C. Franklin

A 32-channel warning system for high working level, fan operation, and airlock-doors has been constructed. The working level monitors have a microcomputer for accumulating the pulses, converting to working level, and triggering an alarm at a variable set point and at one working level. The system also detects when underground fans lose power or air doors are open. The system can detect changes in air velocity which indicate surface fan failures or changes in the ventilation system. Using this alarm system, the ventilation engineer will be alerted prior to excessive levels of radon daughters being reached so corrective action can be taken.

Jan 1, 1981

By David Corkum, David Hatem

Subsurface construction projects are risky ventures and the decision to deliver a project using the Design-Build model does not eliminate those risks. Differing site conditions, inadequate design, and delays will continue to plague some projects. The Design-Build procurement model, however, presents a broad opportunity to allocate those risks much differently than in the familiar Design-Bid-Build model. Starting with a philosophical approach to risk and reward, this paper discusses the continuum of possible risk allocation strategies. It concludes with a proposed optimum strategy in terms of the project’s overall economic efficiency, and points to the dispositive contractual provisions that serve to contour the risks.

Jan 1, 2003

By P. D. Morrell

Jetbelt is the trade name for the air supported belt conveyor. It does not use troughing rollers. Jetbelt conveyors support the conveyor belt on a thin film of air. The belt rides in a steel trough which has small holes equally spaced along the bottom of the trough. Air comes through the holes under the belt, thereby supporting the belt. The air pressure is provided by a single centrifugal blower that creates very low pressure, between 249 Pa and747 Pa [10" and 30" water column], depending upon the tonnage being conveyed. The volume of air required ranges between .001415 m3/S and .00283 m3/S [3 and 6 CFM] per lineal foot of conveyor. Therefore, depending on tonnage being conveyed, a 304.8m[1000'] conveyor might require as little as 1.415m3/S [3000 CFM] or as much as 2.83m3/S [6000 CFM.]. (See Figure 1) Horsepower requirements can be less than troughing idler conveyors and considerably less than some other forms of bulk conveying. Savings are most significant in horizontal and down hill (regenerative) conveyor designs. Horsepower to lift material, of course, does not change.

Jan 1, 1984

By Jeffery Leavy, Ken Davis, Kirk H. McDaniel

The Waste Isolation Pilot Plant (WIPP) is a United States Department of Energy facility located in southeastern New Mexico. It is designed for the safe disposal of transuranic radioactive waste in deep geologic salt beds. Westinghouse TRU Solutions, LLC, the managing and operating contractor, undertook a project to simulate the processes at WIPP in order to identify bottlenecks and optimize available resources. The activities simulated in the model included the receipt, processing and disposal of radioactive waste underground, the mining of new areas for future waste disposal and the transportation of salt out of the mine. The complexity of the processes and the interactive requirements between processes required the use of advanced modeling techniques. The simulation model includes a huge number of locations and path network node points, with movement to and from the locations controlled using parameters rather than explicit routing. Information for the timing and sequence of the mining and nuclear waste emplacement operations is brought into the model via spreadsheets. Arrays in the simulation model keep track of past and future events that occur. Routing to the multiple possible positions in the underground mine is done using attributes, and system functions within ProModel in order to allow for a highly flexible sequence of planned events and to reduce the level of effort in creating the ProModel processing. Considerable use of subroutines in the simulation model is utilized for parametric decision-making that is repetitive. This presentation describes the modeling techniques used to accurately simulate the surface and underground operations. The surface and underground operations are considerably different, thus they will be treated in their own sections.

Jan 1, 2002

By Carl E. Williams

Several years ago it was decided that ASARCO was in need of a good mine scheduling program to complete the computerized open pit mine planning package that was being used on new prospects and operating properties. A trial and error approach was being used to schedule a mine on a year by year basis, but this was time-consuming and far from offering an optimum solution l. Due to the magnitude of time and expertise required to develop such a sophisticated computer program, it was decided to search outside of the company for one already developed and available for purchase, This proved fruitless and therefore proposals were requested from consulting firms that had the expertise to develop such a program. Out of the five firms that submitted proposals, the one chosen was Systems Control, Inc., (S.C.I.) of Palo Alto, California. S.C.I. was selected because it was felt that they offered the greatest capability in the mathematical solution of complex problems. But due to their lack of mining expertise, a cooperative venture was developed whereby ASARCO would supply this mining knowledge. The selection of this vendor, the formulation of the contract and specifications, and the development of the computer program required about 3 years to accomplish.

Jan 1, 1973

By A. L. Mular

Optimization has been defined as the procedure of locating the best of something or the best way of doing something (Mular, 1971). Several texts (Himmelblau, 1972; Ray and Szekeley, 1973; Box and Draper, 1969; and Lee, Adams, and Gaines, 1968) on the subject are available. Such techniques have been placed in two categories, namely, off-line optimization and on-line optimization. For the former, an optimization model is employed; for the latter, a black box approach is involved. The essence of an optimization problem becomes obvious, when a response surface is considered. Suppose that a response (in this case, a criterion of improvement such as profit per day; grade of concentrate per day) denoted by Y, depends only on two variables, X1 and X2, which can be manipulated and controlled. The relationship between Y, X1 and X2 may be represented graphically as shown in Fig. 1. The diagram is called a response surface and its height, Y, is determined by X1 and X2. Points associated with equal responses constitute response contours. The shape is that of a hill, and optimization is the procedure of ascending the hill to reach the top (maximum). In practice, a response surface is subject to disturbances which distort its shape and shift its location from time to time, so that the exact location of a maximum is imprecise. Generally, constraints (restrictions of some sort) on responses and manipulable variables serve to define a region of permissible operation.

Jan 1, 1979

By Donald W. Trepp

Colony Development Operation is a joint venture currently consisting of four active members; The Oil Shale Corporation (TOSCO); Ashland Oil Inc.; Shell Oil Company and Atlantic Richfield Company, operator of the project. The initial efforts on the Colony project began in the spring of 1965. Pilot mining and semi-works engineering programs continued, in phases, to completion in the fall of 1972 when commercialization of oil shale was deemed realistic. Since that time, Colony efforts have been directed toward evaluation of the data collected during the semi-works operation and in designing a commercial operation. In October of 1974, Colony announced: "because of economic and national energy policy uncertainties it was suspending plans to start construction of a commercial oil shale plant on private lands in northwestern Colorado, scheduled for spring of 1975."

Jan 1, 1975

By J. A. Herbst, A. E. Oblad, Y. C. Lo

The major cost in comminution is energy consumption, which can be as high as 50% of the operating cost. Improvements in plant operations have resulted in up to a 15% reduction in energy usage (kw-hr/t). These improvements have been made through the optimization of grinding efficiency and the use of expert model-based control systems. Optimization involves the determination of the levels of the critical-operating conditions that result in the most efficient breakage of ore in the mill. These optimal levels are identified through plant/laboratory test work and through computer simulation using advanced process models. Model-based expert control achieves the maximum performance from the grinding circuit by identifying the characteristics of the ore in the mill with an optimal on-line estimator. Using this information, the control system dynamically determines the operating point that will yield the optimal performance. Two industrial applications of grinding-circuit optimization and model-based control are presented to demonstrate the power of this new technology.

Jan 1, 1997

By R. F. Hüttl

The restoration of surface mining landscapes requires the (re)creation of ecosystems. In Lusatia (eastern Germany), large-scale open-cast lignite mining operations generated spoil dumps widely consisting of acidified, phytotoxic substrates. Amelioration and rehabilitation measures have been developed and applied to these substrates since the 1950s. However, it is still not clear whether these approaches are sustainable. This paper reports on collaborative research work into the ecological potential of forest ecosystem development on typical minesites in the Lusatian lignite district. At first sight, pine stands on minesites along a chronosequence comprising about 35 years did not show differences when compared with stands on non-mined sites of the general region. Furthermore, with some modification, conceptual models for flora and fauna succession in forest stands on non-mined sites seem to be applicable, at least for the early stages of forest ecosystem development. For example, soil organism abundance and activity at minesites had already reached levels typical of non-mined sites after about 20-30 years. In contrast, mine soils are very different from non-mined soils of the test region. Chemically, mine soil development is dominated by processes originating from pyrite oxidation. Geogenic, i.e. lignitic, soil organic carbon was shown to substitute for some functions of pedogenic soil organic matter. Rooting was hampered but not completely impeded in strongly acidified soil compartments. Roots and mycorrhizae are apparently able to make use of the characteristic heterogeneity of young mine soils. Considering these recent results and the knowledge accumulated during more than 30 years of research on minesite rehabilitation internationally, it can be stated that minesite restoration might be used as an ideal case study for forest ecosystem development starting at "point zero" on "terra nova".

Jan 1, 2002

By O. A. Bascur

Based on current sedimentation theory an on-line thickener model was developed and coupled with an extended Kalman Filter to obtain additional information such as the compression zone level and concentration, a corrected underflow concentration, the inventory, and some rheological information. The on-line model was installed and tested for robustness for periods up to three days in an industrial environment giving good results. Emphasis was given to signal processing and selecting the appropriate input variables for filtering. The analysis of the thickener from a phenomenlogical point of view provides for better operation, establishes the limiting operating conditions, and assists in the design of control strategies.

Jan 1, 1986

By P. Chauvet

From a computational point of view calculating a variogram is a perfectly simple operation. For any particular study, we know which variable is to be studied. We also have a good idea of structural parameters which are likely to be important (the scale of the phenomenon, the probable direction of the anisotropy, etc.). Finally, we know the structure of the data file. So we can specify the parameters to be used to calculate the variogram (the distance classes, the angular classes, etc.). This allows us to decide which variogram program is most appropriate (1, 2 or 3 dimensional data, regularly or irregularly spaced, etc. ) . In general, the basic statistics (mean, variance, correlation? etc.) have been calculated beforehand, and so the distribution of the data is already known. Consequently, the choice of the parameter values fed into the variogram is by no means arbitrary. But it must nevertheless be made before the' variogram is calculated. If the resulting variogram is not satisfactory, the whole sequence of operations has to be repeated. Before going on to see how this can be avoided, it is worthwhile having a brief look at the common causes of "unsatisfactory" variograms.

Jan 1, 1982

By Bernard E. Weichman

The oil shales in the Piceance Creek Basin of northwest Colorado occur in the Parachute Creek member of the Green River formation. The oil shales were deposited in a unique environment of deposition which caused the mineral nahcolite (NaHC03) to be precipitated within the oil shales. Post-depositional tectonics resulted in extensive fracturing of the Middle Zone of the Parachute Creek member, and to a lesser degree portions of the Lower Zone, which allowed percolating ground waters to dissolve the nahcolite in the fractured portion of the oil shale beds which is characterized by broken porous oil shale, certain beds of which have collapsed into rubble and debris. The extent and porosity of the Leach Zone aquifer is dependent upon the percentage of kerogen and nahcolite originally deposited in the oil shale. Any oil shale development program in the Piceance Creek Basin of northwest Colorado will need to be preceeded by an extensive study of the Leach Zone in order to determine the effects on a mining program.

Jan 1, 1973

By H. Dr. Boldt, J. Dr. Henneke

PREFACE In German coal mines the application of tunnel boring machines has become a very effective and economic technique for major development works. After initial trials around 1970 the breakthrough was reached by driving 13 km of road ways on Rheinland and Friedrich Heinrich collieries, using a DEMAG tunnel boring machine of 6 m diameter. INTRODUCTION The coal mines of Rheinland and Friedrich Heinrich are to be found in the West of the Ruhr Area, the largest coal mining area in the Federal Republic of Germany (Table 1). They form part of the Ruhrkohle company. Rheinland coal mines produces 41000 to 43000 t of run-of-mine coal every day, of which 20500 t are usable coal. Friedrich Heinrich has a daily production of 17000 t of run-of-mine coal, 9000 t of which are usable. The coal is worked at depths of 600 to 1100 m in seams 0.6 to 3.0 m thick. The method of mining is longwall, and the machines used are ploughs and shearer loaders. From 1973 to 1980 a programme was put into operation in these two mines to develop and open up the coal field on the 885 m level. A total tunnel length of 20 km was to be driven. After thorough investigations it was decided to employ a full-face tunnel boring machine for

Jan 1, 1981