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By B. E. Ydstie, B. F. Lund, K. R. Løvåsen, B. A. Foss

The paper presents sensitivity analysis for a dynamic model of submerged arc silicon furnaces. The model we study, called ?Simod?, was developed by Elkem in cooperation with NTNU and Sintef. It is today a much used tool in Elkem for operator training and analysis of the dynamic behaviour of the silicon production process. The aim of our work is to bring the simulator tool closer to industrial practice, and construct a mechanism to adapt the model to the behaviour of a running process, online. The paper presents the results of the sensitivity analysis that has been undertaken for important parameters in the Simod model. The parameters associated with the process inputs are electric power loss, loss of fixed C and reactivity of carbon. The output signals that have been investigated are fed quartz, tapped silicon and silica. The paper also interprets the results of the sensitivity analysis in a process operation context.

Jan 1, 2004

By Patrick J. Doig

The contract for the construction of the Inline Pump Station for the Milwaukee Metropolitan Sewerage District involves the sinking of three shafts and the excavation of a pump chamber. The shafts are being sunk to a depth of 104 meters and pass through 52m of sediments before encountering dolomitic bedrock. The pump chamber is constructed in dolomite. The sediments are alluvial, estuarine and lacustrine in origin, with some ice margin deposits. They comprise loosely consolidated fine to coarse grained sand, silts, clays and gravels, and they are heavily saturated with a water content often above 60%. The water table is at a depth of 3m. The dolomite is silurian, generally dense, with some clay-filled vugs and shale partings. Until 1983, underground construction in the Milwaukee area had been limited to depths of 26m in the sediments and 20m in the dolomites. Water control methods had included caissons, compressed air, extensive internal and external dewatering, and grouting. Flows of 20 liters per second were commonplace with as much as 80 liters per second being encountered in the rock. However, in 1984 work was commenced on the deep sections of the Milwaukee sewerage scheme with the letting of three major contracts including the Inline Pump Station. With excavation taking place at greater depths, it become obvious that previous methods of water control would be inappropriate. To protect against major inrushes of high pressure water in the rock, an extensive program of pre-grouting from the surface was specified. Water control in the sediments was left to the discretion of the contractor and in each case freezing was choosen. This paper describes in detail the grouting and freezing procedures.

Jan 1, 1985

By C. M. Young

THE following paper has been prepared with the object of placing on record in the Transactions some facts concerning the present condition and future prospects of the coal industry of Illinois. In presenting it, the writer wishes to say that a considerable amount of the material contained is taken from the publications and records of the Illinois Coal Mining Investigations, the annual Coal Report of the State Mining Board, and the work of the State Geological Survey. Coal Beds and Mining Methods According to the latest maps of the State Geological Survey, there are only 19 of the 102 counties of the State some portion of whose territory is not within the borders of the coal measures. If outlying areas in Calhoun and Whiteside Counties are considered, the number is reduced to 17. This does not mean that all of the 85 counties that are partly or wholly underlain by coal measures will become producers, as there are some portions of the State in which the coal does not occur in beds of such thickness as to warrant the hope that it can be mined. The mining of coal is widespread, however, for in 1916 there was production from 51 of the 102 counties of the State. There seem to be no cases in which operations will be limited by depth, as none of the coal measures lie at depths much greater than those at which it has been proved that coal may be profitably mined in this field. In fact, the deepest shaft reaching a bed of bituminous coal in the United States is located in this State at Assumption, where coal only 3 ½ ft. (1.07 m.) thick is worked at a depth of 1004 ft.. (306 m.) The coal beds occur in the form of a basin which is deepest along a line extending through the central part of the State and bearing a, little west of north. The northern, western and southern borders of this basin lie within the boundaries of the State, but on the eastern side the Illinois field is continuous with the Indiana field. The glacial drift covers all except the extreme southern end of the State and the visible outcropping

Jan 9, 1917

Experiment of Improving the Quality and Decreasing the Impurity of Titanium Concentrate in Panzhihua Mine in China

Sep 13, 2010

A series of stemming confinement tests were conducted at a test site near Vernal, Utah. The purpose of the study was to determine the relative performance of various stemming enhancement “plugs”, stem types and loading configurations. The stemming performance was quantified in terms of: . Stem confinement time . Stem ejection velocity . Ground swell velocity . Ground vibration . Air blast . Crater formation Of primary interest was the performance of a new spherical stemming enhancement plug. The initial findings indicate that the hard plastic spheres improved blast performance when used appropriately. Their ability to improve blast performance is reduced when used in over confined or severely underconfined conditions. The study also evaluated the effects of air decking on stemming confinement and explosive performance.

Jan 1, 2000

By N. Kornelius

In recent years there has been an increased focus on corporate governance matters worldwide. The duties and responsibilities of directors of companies have come under close scrutiny, with shareholders increasing their demands for greater responsibility and accountability. Media attention and pressure groups have also had their effect. Governmental actions have supported these demands and directors have witnessed sweeping legislative changes imposing more onerous duties and liabilities than formerly imposed upon them at common law and in terms of the Companies Act. At the same time, the power of regulatory bodies has been increased to enforce this legislation and make someone pay to remedy an alleged infringement. Breach of such duties may incur personal or criminal liability, or both. Environmental protection legislation has become a particularly prevalent feature in this regard, and the number and complexity of statutes concerning the environment have increased over the past few years. Directors of South African companies will be familiar with relevant acts such as the National Environmental Management Act 107 of 1998; Conservation of Agricultural Resources Act 43 of 1983;Hazardous Substances Act 15 of 1973, as well as the National Water Act 36 of 1998. Now the directors of mining companies are faced with the Mineral and Petroleum Resources Development Act 28 of 2002.

Jan 1, 2003

By José Arce

El sistema AG-DAS entró en operaciones en 2015 y su aplicación tiene diversas ventajas sobre el método de polarización inducida convencional. El concepto del sistema fue el uso de múltiples receptores de dos canales, que registran la señal completa con sincronización de tiempo por GPS. La tecnología DAS (sistemas de configuración distribuida, por sus siglas en inglés) brinda mayor confiabilidad en la detección y modelamiento tridimensional de mineralización metálica con geometría compleja a profundidades de hasta más de 800 metros.

May 22, 2019

By Dennis E. Mitchell

The need to develop and field explosive, pyrotechnic and propellant initiating systems that have high reliability and extraordinary safety requirements has led to the exploration and development of several materials and initiation systems at our laboratories. Our approach to initiating device development encompasses five main areas; energetic materials development , device physics, theoretical analysis and model development and experimental verifications

Jan 1, 1995

By Kjell Winther

"Hydralift Scanmec introduced early in the eighties a new and different mill design for very large grinding mills. The design described has actually no size limitation upwards and is so far suggested with motor power up to 40 MW. The mill is furnished with gearless ring motor drive transmission. It is totally fabricated, without heavy castings. The first installation, an 8, 1 MW ball mill dia. 6,5 m x 9,65 m length, has been in continous operation in 13 years without problems. Total grinding costs has been reduced with 3 0% compared to traditional smaller mills. Reductions has been achieved in maintenance cost, power consumption, liner wear and grinding media consumption.So far 3 ball mills of the described design are delivered and in operation, one grinding Iron ore and two grinding Nickel ore.IntroductionThe design of mills for mineral ore dressing has basically been unchanged since grinding in mills started some I 00 years ago, in spite of the fact that mills have grown larger and larger. This has resulted in structural and mechanical problems, causing expensive failures and loss of production.Hydralift Scanmec engineers were designing mills for more than 20 years according to the old «rules». As they experienced interest for an increase in the mill size at the time when reports about failing mills were published, they started analyzing the different mill parts to find new solutions. One goal was to only use elements from proven technology in the new design. Two key items were ring motor (wrap around motor)(Isch et al. 1977, Meintrup and Klein 1982, Ranze 1983) and large diameter pad bearings (wrap around bearings)(Fuller 1984), both acknowledged from other industries."

Jan 1, 1995

By L. J. Vincze

The high cost of constructing mineral processing plants in remote locations warrants a close examination of the alternatives available for reducing the amount of on-site construction work. Among the alternatives are portable process plants, modular design and barge mounted plants. Each alternative has certain advantages as well as limitations depending upon specific conditions. On the basis of practical experience and engineering analysis, the paper examines the potential benefits to be realized by these techniques and summarizes the conditions required to obtain them. The potential savings indicated by such studies should encourage consideration of innovative design features for new plants located in remote areas.

Jan 1, 1980

By Mishark Nnabuchi

A heterojunction of PbS - CuS thin film has been grown on glass slides by SGT. The films were annealed for 1hr at temperature of 373K and 423K respectively. The optical properties were characterized using a UNICO UV - 2102 PC Spectrophotometer at normal incidence of light in the wavelength range of 200 - 1000nm. The minimum percentage transmittance was observed to be 34% for sample A and 25% for sample B within the same optical region. The band gap energy was determined from the spectra to be 2.05eV for sample A and 1.85eV for sample B which gave a band shift of 0.20eV. It can thus be concluded that the optical properties of the films within the VIS - UV - NIR can find application in solar thermal technology, particularly as antireflection coating, window materials and as good materials for selective solar cell fabrication.

Jan 1, 2010

[Executive J. V. W. REYNDERS, Chairman WILLIAM H. BASSETT E. DEGOLYER I-I. C. BELLINGER RICHARD PETERS, JR. Finance GEORGE OTIS SMITH, Chairman H. A. GUESS F. JULIUS FOHS Admissions GEORGE D. BARRON, Chairman DAVID LEVINGER P. A. MOSMAN H. K. MASTERS J. A, SINGMASTER Alternates F. G. BREYER C. W. HAMILTON F. E. PIERCE]

Jan 1, 1928

By Raja V. Ramani

As the new millennium approaches, it is appropriate to assess the progress that has been made in mine health and safety, a matter of concern to management, labor and government. One can hardly look at the major events of the last century — from the birth of the US Bureau of Mines through the enactment of the modern health and safety laws — without realizing that the march has been relentless toward eradication of health and safety threats in mining. The progress is spectacular in mine safety and significant in mine health. In looking at the future, it is safe to assume that societal demands will increase for improved health and safety conditions in the workplace. So will the demands for greater technological leaps. The standards will for measuring success and the expectations of progress in creating a safer and healthier mine environment will grow. The possibilities are enormous of meeting these exacting requirements in the 21st century.

Jan 1, 1999

Ongoing rockpass problems on mines within the South Africa region, prompted AngloGold Ashanti to embark on a risk assessment of major rockpasses. This commenced with the collection of relevant data to identify gaps in the available knowledge and identify existing problems. This was followed by an assessment of rockpass layouts to determine existing and potential interactions with other excavations. An initial risk assessment has been completed and the rockpasses have been ranked in terms of their risk profile. The lack of geological data and an easy and reliable method of surveying rockpasses have been identified as problem areas. Shortcoming is terms of rockpass management procedures have also been identified. Further work is required to quantify the risk in terms of probability of occurrence and consequences.

Jan 1, 2005

By Christopher Mark

Multiple seam interactions are a major ground control hazard in many U.S. underground coal mines. The two most common types are: ? Undermining, where stress concentrations caused by previous full extraction in an overlying seam is the primary concern, and; ? Overmining, where previous full extraction in an underlying seam can result in stress concentrations and rock damage from subsidence. The National Institute for Occupational Safety and Health (NIOSH) has completed a major study aimed at helping to identify the location and likely severity of these interactions. In the course of field visits to mines throughout the U.S., more than 300 multiple seam case histories were assembled into the largest data base of multiple seam case histories ever collected. These data were analyzed with the multivariate statistical technique of logistic regression. The study also employed LaM2D to estimate the multiple seam stresses, ALPS and ARMPS to determine pillar stability factors, and the CMRR to measure roof quality. The study resulted in the development of a computer program, called Analysis of Multiple Seam Stability (AMSS), which can help mine planners to evaluate each potential interaction and take steps to reduce the risk of ground control failure. AMSS first evaluates pillar design by calculating the single seam Stability Factor (SFSS) using ALPS or ARMPS. It also automatically generates a LaM2D analysis that provides the additional multiple seam stress so that the final, multiple seam SFMS can be determined. The second part of the AMSS procedure builds upon the statistical findings that overmining is much more difficult than undermining, isolated remnant pillars cause more problems than gob-solid boundaries, and weaker roof significantly increases the risk of multiple seam interactions. AMSS quantifies these effects and predicts the outcome in terms of three levels of risk: GREEN (where a major multiple seam interaction is considered unlikely), YELLOW (where adding a pattern of cable bolts or other equivalent supplemental support could greatly reduce the probability of a major interaction.), or RED (a major interaction should be considered likely, and it may be desirable to avoid the area entirely).

Jan 1, 2007

To the members of The South African Institute of Mining and Metallurgy We have audited the annual financial statements of The South African Institute of Mining and Metallurgy set out on pages 451 to 460 for the year ended 30 June 2002. These financial statements are the responsibility of the Institute?s Council. Our responsibility is to express an opinion on these financial statements based on our audit. Scope We have conducted our audit in accordance with statements of South African Auditing Standards. Those standards require that we plan and perform the audit to obtain reasonable assurance that the financial statements are free of material misstatement. An audit includes: ?examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements, ?assessing the accounting principles used and significant estimates made by management, and ?evaluating the overall financial statement presentation. We believe that our audit provides a reasonable basis for our opinion. Audit opinion In our opinion, the financial statements fairly present, in all material respects, the financial position of the Institute at 30 June 2003 and the results of its operations and cash flows for the year then ended in accordance with South African Statements of Generally Accepted Accounting Practice. Auditors 29 July 2003 Council?s approval of the annual financial statements The annual financial statements for the year ended 30 June 2003 set out on page 451 to 460 were approved by the Council on 26 July 2002 and are signed on its behalf by:

Jan 1, 2003

By J. I. Paige

As part of a continuing effort to develop technology that maximizes mineral and metal recovery from domestic resources, the Bureau of Mines investigated a method to totally utilize copper converter slags without recycling them back through the matte smelting furnace. The research was directed toward (1) recovering the contained copper in converting slags by producing a recyclable copper-iron matte, (2) carbothermically reducing the slags to recover the iron, and (3) producing slag wool from the depleted slags. This report deals with the reduction of three industrial converting slags, containing 2.0 to 7.3 wt-pct Cu, in an 800-kVA electric arc furnace to produce a recyclable copper-iron matte. The addition of sufficient iron pyrite to provide 29 to 113 pct of the stoichiometric sulfur (based on producing 40-pct-Cu matte) produced a recyclable matte (36 to 61 pct Cu) at an energy consumption of 520 to 700 kWh per ton of solid material charged. The expected energy saving for treating molten slag in an electric furnace (5-to 9-MVA range) is about 400 kWh per ton of molten slag treated.

Jan 1, 1982

By M. Dattilo

The U.S. Bureau of Mines has been conducting research on the use of waste-derived zinc as a partial replacement for pure zinc in the electrogalvanizing process. The end product of this process is automotive sheet, which has enhanced cosmetic protection over previously used cold-rolled (CR) steel. In this study, primer-coated specimens of CR and electrogalvanized (EG) steel were subjected to the on-vehicle environment and monitored periodically by electrochemical impedance spectroscopy (EIS) during immersion in 1M NaCI solution. The results of these tests were compared with immersion-only conditions. Scanning electron microscope (SEM) and energy-dispersive X-ray (EDX) techniques were also used to evaluate the corrosion processes and compare them with atmospheric exposure specimens. EIS was found to measure the corrosion associated with on-vehicle exposure, thus providing an excellent screening technique for evaluation of the performance of EG automotive sheet steel.

Jan 1, 1990

By D. K. Steele

An 18-in-diam column water elutriator was designed, tested, and operated by the Bureau of Mines for recovering nonferrous mixed metals from automobile shredder rejects. The waver elutriator separated metals from nonmetals contained in shredded nonmagnetic rejects. The unit was constructed and integrated into a local automobile shredding operation. Nonmagnetic rejects from the automobile shredder were fed onto the surface of a column of rising water. Dense materials fell through the rising water and were collected as a sink product at the bottom of the column; medium-density materials were removed as an intermediate product in a water flow through a discharge port located between the overflow and sink; and light materials were immediately carried out in the overflowing water at the top of the column as a float product. Nearly 99 pct of the mixed metals were recovered from the nonmagnetic rejects as a 70-pct-metal concentrate. Other operating conditions yielded a 93.7-pct-pure-metal product resulting in a 93.1-pct metal recovery. Float rejects are combustibles, light plastics, foam rubber, and minimal amounts of coated and uncoated copper wire. The middling discharge contained mainly medium-density rubber, plastics, glass, rock, coated and uncoated copper wire, and frequently some thin-sheet stainless steel and wrought aluminum. Maximum metal recovery in the operating program was achieved using a water velocity of 52 fpm (650 gpm). Maximum purity was obtained with a velocity of 88 fpm (1,100 gpm). .Water was recycled through a 12,000-gal baffled clarifying tank. Entrainment water losses with the float and middling rejects averaged 50 gpt of reject feed. Records maintained by the shredder operator show a 34-pct increase in nonmagnetic metals recovery during a 1-yr operation of the water elutriator as compared to recoveries from a previously used air classification system.

Jan 1, 1983

By D. R. Flinn

A newly developed chemical conditioning technique, which greatly simplifies the preparation of plating baths for the electrodeposition of titanium diboride (TiB2) coatings, is described in this report. The new plating technique was used to prepare samples of titanium diboride (TiB2) coatings on three types of substrate materials. These samples were then evaluated in both low- and high-speed wear-test programs to determine the wear resistance, microhardness, and adhesion of the coatings. In general, it was found that the wear resistance of the coatings is independent of substrate. Scanning electron micrographs have shown that the coating wear surfaces are very smooth, suggesting slow and continuous removal of the coating during the wear test (that is, adhesive wear). Adhesion between the coating and all substrates was excellent. Microhardness results show that the TiB2 coating is harder than alumina, with a hardness value exceeding 5,000 kg/mm2 measured in one test. The results of the wear tests show that TiB2 coatings have relatively poor wear resistance compared with alumina in low-speed unlubricated sliding environments, but exhibit wear properties comparable with alumina in high-speed unlubricated sliding environments.

Jan 1, 1981