Search Documents

By I. Iwasaki, T. Fujuita

The removal of phosphorus from steelmaking slags is essential for recycling such slags to blast furnaces for recovery of their manganese, iron, and lime contents. Phosphorus is mainly concentrated in the dicalcium silicate phase of the slags (Fujita and Iwasaki, 1988, 1989; Suito, et al., 1977). Slow-cooling of steelmaking slags in an air atmosphere increased the grain sizes of constituent minerals; however satisfactory magnetic separation results could not be attained because of the close association of a strongly magnetic ferrite phase with dicalcium silicate (Fujita and Iwasaki, 1988). Curie point of the strongly magnetic ferrite phase in the slow- cooled steelmaking slags was investigated and an attempt was made to separate the phosphorus-bearing dicalcium silicate phase in ground slag pulps heated to a temperature exceeding the Curie point. Materials and methods Slag samples, heated to its fusion temperature of 1370°C and slow-cooled in an air atmosphere, were ground dry to -90 µm (about 170mesh) in a ring grinder. The ground sample was pulped to 1% solids in distilled water using 1 kg/t sodium hexametaphosphate as a dispersant and separated in a Sala high gradient magnetic separator, Laboratory Model 10-15- 20B, using a 100-mesh expanded metal matrix and 300 m/h flow rate.

Jan 1, 1990

By S. C. Suboleski, J. W. Oberholzer

This paper describes research being undertaken by the Chamber of Mines Research Organization (COMRO) to assist the continuous miner operator and section foreman in the performance of their jobs. The project will initially provide visual assistance to the miner operator, and later it will semiautomate the mining (cutting) process. Using a technique known as "RF tagging," the project will also provide the section foreman with real-time or near-real-time information about the performance of the loading and hauling units. This data will allow the section foreman to quickly detect problems and take action where appropriate. The project is based upon the application of currently available technology, and in-mine testing results from the first phase are now available.

Jan 1, 1994

By Y. K. Yen, J. D. Miller, C. L. Lin

Particle size segregation is a common phenomenon in many particulate processes and has many undesirable effects. The size segregation which occurs on a belt conveyor causes a serious problem for on-line particle size measurement using image-based techniques. Whether particle size distributions measured from the top layer of the belt are representative of the total particle population is largely dependent on the degree of size segregation. Therefore, it is important to understand the nature of such size segregation in order to make appropriate corrections for on-line particle size analysis. Monte Carlo simulation has been used to provide segregation information on particles with simple geometry and the results can help to determine important factors in experiments with irregularly shaped particles. It is expected that the relationship between the particle size distribution of the top layer and that of the entire particle population on a belt conveyor can be formulated as a model based function.

Jan 1, 1997

By Richard H. Adams

INTRODUCTION With the discovery and depletion over the years of near surface ore bodies, exploration targets are tending to be at greater depth or overlain by various types of overburden which in some cases extends to considerable depth or is heavily water bearing. Access to these types of deposits for exploration and development often requires vertical shafts. This paper discusses the concept of small shaft engineering and construction, primarily for underground exploration but also for use as a low tonnage production facility or for mine ventilation. The option of a small shaft may be attractive in a number of cases, some of which are: The underground exploration of a deposit at depth where minimal expenditure is desirable until the potential of the deposit has been determined. The exploration shaft in many cases later serves as a ventilation way and second means of egress. Production of ore in a small tonnage/high-grade operation where decline access is impractical. For ventilation where other types of openings are impractical or would delay start-up of mine operations.

Jan 1, 1987

By Charles A. McLean

Bucketline dredges are machines for excavating large relatively unconsolidated or weakly consolidated materials from below water level. They are at the upper end of the capital cost range and the lower end of the operating cost range for placer mining machines and have digging capacities, typically, of from 100 cubic yards of bank measure material per operating hour for a shallow digging dredge carrying 2 cubic foot buckets to 1500 cubic yards per hour for a large deep digging dredge with 33 cubic foot buckets. Bucketline dredges used in the mining industry have their mineral processing plants mounted aboard the digging hull. Since dredges are high capital cost items, they require large ore reserves, typically at least ten years. Because of their high capital cost they are usually operated around the clock and for as many months of the year as weather conditions will permit. Typically a well run dredge operating year round would be expected to operate for 600 hours per month. Dredges operated in cold climates cannot operate when the weather freezes the dredge pond or the gravels, and dredges operating at sea cannot operate when high waves might batter the digging ladder against the bottom or upset the mineral extraction process.

Jan 1, 1992

By Ümit Yasar Onder, Tevfik Prof. Dr. Güyagüler

This paper describes the results of an investigation done to determine thermal properties and heat emission of coal measure rocks in Karadon district of Zonguldak Coal Colliery. In Karadon District, depth of working level is about -600 m where the heat problem arises. In the near future, workings will be at deeper levels and working conditions will be more difficult due to high heat emission. At the beginning of the paper the importance of wall rock heat emission in underground mine have been explained and then the amount of heat emission to the ventilating air has been calculated. It has been found out that the strata is the main source of heat in the mine. Therefore, geothermal gradient of the region has also been determined simply by measuring the virgin rock temperatures in different levels of the mine. All other data directly related with heat emission from different sources has been collected and has been analyzed by using a special computer package. As a conclusion, total heat and moisture content in ventilating air and heat balance has been determined for Karadon Coal Mine. In addition, some recommendations and suggestions have been made for the future works when the mine workings go to the deeper levels.

Jan 1, 1995

There has been some confusion over the selection of discount rates when performing stochastic simulations of a project's net present value (NPV) using risk- adjusted discounting techniques. Some argue that lower discount rates should be used when performing stochastic valuation simulations. This creates higher NPV values and improves the attractiveness of a project. Others argue that the discount rate should not be lowered for these simulations. This paper exposes the source of this confusion. It demonstrates that stochastic simulations do not remove the risk inherent in a project and, therefore-do not improve a project's value to the risk-averse investor. Risk-adjusted discount rates should, therefore, not be adjusted downward when performing stochastic NPV simulations. Stochastic simulations are, however, shown to he useful in several aspects of project valuation.

Jan 1, 1996

By L. Xiao, P. Somasundaran

Three major types of solution chemical equilibria-involving minerals, solution, and flotation reagents such as collectors, frothers and modifiers-play a crucial role in determining the behavior of complex flotation systems. Minerals of phosphates (apatite and francolite), tungsten (wolframite and scheelite) and associated carbonates (calcite and dolomite) are sparingly soluble in aqueous solution and form dissolved mineral species in bulk solution. Such dissolved species interact with mineral solids, often resulting in surface conversion of the minerals. In addition, they can interact with various floation reagents and lead to surface or bulk precipitation and loss of selectivity in the flotation. Relevant solution equilibria of such sparingly soluble minerals and their interactions with oleic acid and structurally modified reagents were determined in this study using a multi-pronged experimental approach. Methods to manipulate and control the solution chemical equilibria and thus achieve selectivity in flotation systems are discussed.

Jan 1, 1992

By K. Hanumantha Rao, K. S. E. Forssberg, B. -M. Antti

Selective flotation of muscovite from a material containing muscovite (15.4%), biotite (13%), and siliceous gangue (quartz and feldspar), using a mixed collector system of sodium oleate and dodecylamine acetate has been described. Muscovite is found to float in preference to biotite, when the pulp is initially conditioned with oleate followed by amine at basic pH values. The results indicate that a product containing 63% muscovite with a recovery of 93% can be obtained, while using 75-150glt of oleate and 96 g/t of amine. The biotite grade and recovery are found to be around 30% and 20%, respectively. A good selectivity between muscovite and siliceous gangue is obtained. A final product containing 95% muscovite with an overall recovery of 75% is obtained when the flotation concentrate is subjected to magnetic separation. These studies indicate the possibility of separating muscovite from biotite by using a mixture of collectors.

Jan 1, 1991

By V. R. Manukonda, I. Iwasaki

Selective flocculation of iron ores is extremely sensitive to the type and amount of soluble salts in pulp solutions. Chemical precipitation of alkaline earth ions combined with ultrasonic treatment deactivates their adverse effects without using any environmentally ill-defined reagents. The manner in which ultrasonic treatment affects starch adsorption on hematite, dissolution of quartz, and the selective flocculation process was investigated. Selective flocculation tests were conducted in the presence of up to 400 ppm calcium ion on a quartz-hematite mixture by precipitation as calcium carbonate, and the role that silicate ion generated by ultrasonic treatment plays in achieving the selectivity of separation is discussed.

Jan 1, 1988

By J. Partyka, Trevor R. J. Kelly

This paper presents the results on noise testing of a fan only, as well as the results of a steel silencer and of flexible silencers that were connected directly to a fan. On-site facilities and free-field method set by the British Standards Institution were used to measure and then compare the fan only and different practical silencer configuration setups. In order to determine the fan-silencer combination that would give the maximum noise attenuation, total noise intensity, noise contributed to by the fan motor only, as well as aerodynamical noise created through air interacting with the fan parts were considered to obtain decibel readings for the octave bands. Subsequently, the optimal configuration found was the setup with flexible silencers on the fan inlet and the fan outlet. If only one silencer is used, it should be installed on the fan inlet. The aerodynamic noise affects the low frequencies. The flow noise is then overtaken at 1 kHz by the mechanical noise.

Jan 1, 1995

By L. W. Scott, T. H. Dubaniewicz, F. T. Duda, P. G. Kovalchik

Recent research conducted by NIOSH's Pittsburgh Re¬search Laboratory showed that electrical current levels permitted under present regulations may not limit cable temperatures to less than 90°C in reeled trailing cables. Reeled cables, which are tightly wrapped with many turns and which carry current in an enclosed space, can become overheated due to poor heat transfer. This overheating can cause the cable insulation to soften, making them prone to damage. The damaged insulation reduces the life of the cable and can lead to shock, electrocution and mine fires. This paper describes a method of measuring the conductor tem¬perature of mine trailing cables during normal operation. The temperature is measured using a 50/125-, µm graded index multimode optical fiber located in the center of the metallic conductors. Distributed temperature measurements are made using an optical time domain reflectometer (OTDR). This system is capable of measuring temperatures with an accuracy of ± I °C over a length of 4 km at I -mintervals. With this unique way of measuring temperature, tests can be conducted that simulate actual mine conditions. The tests provide important data that allows MSHA's Approval and Certification Center to develop approval criteria for cycli-

Jan 1, 2000

By W. E. (Bill) Stanley

Introduction This is an exciting day. It isn't often that you can find the best minds in a particular business gathered together in one place. But that is what we have here. You are the best and the brightest people there are in the business of gold mining. What we discuss at this conference confirms the major issues facing us and sets out the issues governing how our mines and mining companies will be run in the next few years. In looking over the list of papers to be given, I have noticed something. It is something that I have noticed at almost every mining convention I have ever attended. Almost every paper at this conference concerns itself with the technical side of mining. Most of us in this roan are professionals; we are either engineers, geologists, accountants or representatives of some other profession. In getting where we are today, we have had to work hard to acquire the technical skills needed for our individual professions. We are all proud of our knowledge and work hard to claim the right to be considered an expert in a particular technical field or subject area.

Jan 1, 1987

By W. C. Patrick

The Spent Fuel Test-Climax (SFT-C) was con- ducted to evaluate the feasibility of retrievable deep geologic storage of commercially generated spent nuclear-reactor fuel assemblies. One of the primary aspects of the test was to measure the thermomechanical response of the rock mass to the extensive heating of a large volume of rock. Instrumentation was emplaced to measure stress changes, relative motion of the rock mass, and tunnel closures during three year of heating from thermally decaying heat sources, followed by a six month cooldown period. The calculations reported here were performed using the best available input parameters, thermal and mechanical properties, and power levels which were directly measured or inferred from measurements made during the test. This report documents the results of these calculations and compares the results with selected measurements made during heating and cooling of the SFT-C.

Jan 1, 1986

By C. Ceccarini, I. Salvadori, G. Oggiano

GENERAL BACKGROUND The first mention of the presence of bauxite in the mesozoic series of north-west Sardinia (fig. 1) is owed to Oosterbaan, a Dutch geologist, who carried out a geological survey of the area in the ninetten thirties. A more detailed study of the mesozoic series was attempted in the fifties by Pecorini and other, who concentrated particularly upon the stratigraphy of the bauxitic horizons, through examination of the various outcrops. In the sixties a pining company, Monte Amiata S.p.A., turned its attention to a section of the deposit outcropping near Olmedo and, considering it to be of some promise, carried out prospecting works consisting essentially of various trenches, some bore holes, a few adit and a. layout plan for the preparation and execution of trial exploitation. The results, although positive, did not convince the company's shareholders to continue the exploration. This report, which is intended as a new contribution to knowledge of the Sardinian bauxite deposit, takes into account the information acquired not only from a drilling prospection begun in 1979 in connection with the SOMIT-PROGEMISA joint venture, but also the results of structural studies and numerous chemical, mineralogical and

Jan 1, 1984

By J. Litsenberger, T. E. Marshall, P. R. Coyle, L. J. Prosser, A. T. Iannacchione

For the first time in an underground stone mine, the relationship between roof movement and microseismic emissions was examined in conjunction with two distinct roof fall areas. As roof monitoring increases in acceptance and monitoring technology advances, the goal of providing reliable roof fall detection systems to enhance the safety of underground mine workers moves closer to reality. Instrumental to reaching that goal is the ability to interpret accurately and completely roof movement and microseismic emissions, which can serve as precursors to roof falls. This paper examines the capabilities of convergence and microseismic monitoring systems to better understand roof rock failure mechanics and to anticipate roof falls. An understanding of how these techniques are used and how they interact with each other is critical in developing the most effective ground control strategy for our nation’s mines.

Jan 1, 2004

By Neil J. Duncan, Edward R. Langfield

A hydraulic rock breaker was developed in Germany by Helmut Darda and uses a wedge-plug and feathers mechanism powered by a 10,000 p.s.i. power pack. During the past four years these tools have been increasingly used all over North America for secondary breaking of boulders and rock. More recently, techniques have been developed to break rock off the solid in trenches and rock emplacements where blasting is pro¬hibited or very limited. Underground operations are commencing to adopt the splitter for scaling plus including systems which can be efficiently applied to chambers and mines. Mr. Neil Duncan, who was originally scheduled to give the main part of this presentation has, during this past month accepted a position with the Alberta Energy Resources Conservation Board in Calgary. The board encourages its members to take part in seminars such as this but, unfortunately, due to the heavy pressure of work, it was impossible for him to attend this conference. Mr. Duncan has, however, forwarded me his notes and suggest¬ions, and using these, combined with a slide presentation, we feel that we can quickly and clearly define the operations and application of the hydraulic splitting technique as it applies to your profession and tunnelling work. The first question that most of you are asking is, "Why use a hydraulic splitter if you can blast?" Our answer to this is that we are not advocating the use of hydraulic splitting where blasting is feasible - but, during the past decade many applica¬tions have arisen where blasting is not allowed, or restricted

Jan 1, 1997

By W. R. Dearman, N. Turk

A seismic fissuration index (K) is defined as the ratio of the difference in the P and S wave velocities obtained when a dry rock specimen is tested both under a load equal to half the uniaxial compressive strength of the rock (Vo) and without an applied load (Vd) to the velocity obtained without an applied load (Vd), as K = (Vo - Vd)/Vd. A similar seismic fissuration index is also proposed for classifying the dry rock mass in terms of field seismic velocities. The field equation is extended by including the intact rock seismic velocities. K is found to be related to the porosity of rocks. The proposed equation can equally be used for characterizing saturated rocks, using S-wave velocities. However, the time average equation should be used for characterizing saturated rocks, using P-wave velocities, even though this equation gives upperbound estimates of the rock material and fracture porosities.

Jan 1, 1986

By E. C. H. Becker

When data points, plotted on X-Y coordinates, lie along a simple line, their regression can be matched to a high degree of accuracy by one or other simple algebraic expression (Boot and Cox, 1970). Under these conditions, interpolation is axiomic. Further, if the expression defines no more than a straight line, a parabola or other such line which can be related to some specific mechanism which generates the points, then extrapolation might be valid. However, any extrapolation would depend on the continued, unchanged functioning of the mechanism. Studies of more intricate assemblages of data points have long been based on representation by means of series (Fourier, 1811). If sufficiently complicated, several different algebraic expressions can represent the same intricate regression accurately (Hoerl, 1954). However, without reference to a mechanism, no extrapolation is contemplated. Typically, variations in the prices of minerals with time are. sufficiently complicated to render invalid any simple attempts at extrapolation. The computer, however, can be used to derive algebraic expressions which match complicated regressions and also can be represented by the functioning of a mechanism (Becker, 1984). The techniques involved have been applied with advantage in the study of time series representations of mineral prices.

Jan 1, 1986

By Lane White

Environmental regulations have become a decisive factor for many minerals industry operations. Managers face new liabilities as a result of environmental laws, and restrictive permitting requirements for new projects make mine development an increasingly difficult proposition. An abundance of federal, state and local environmental laws and regulations already confront on-going minerals operations, and complex new legislation and rule-making is always in progress. Acronyms and initials like RCRA, CERCLA, SARA and EIS become as familiar as reserves, tons, grades and recoveries. The growth of such regulation has created a new category of professional employees - environmental scientists and engineers-whose presence will influence minerals production activity from now on. The disciplines of environmental science and engineering are still being defined. While these definitions are being worked out, companies in the minerals industry have responded by hiring people with professional experience in existing disciplines and training them to their special needs. An environmental consulting industry of substantial proportions has developed to offer expertise where producing companies may not find it economic to hire full-time professionals. The mining schools have responded by introducing environmental course work, but these programs have yet to supply a significant number of environmental professionals to the minerals industry. To gain some perspective on where minerals producers now stand in their hiring of environmental professionals, ME recently surveyed 20 companies, with questions about how they go about the business of managing environmental compliance. Twelve companies re¬sponded to the survey, and the results

Jan 1, 1991