Search Documents

By Marcella Gautê Cavalcante Xavier

A presente proposta tem por objetivo desenvolver uma análise experimental da liga hipereutética Sn-0,5%Ni solidificada unidirecionalmente em regime transitório de fluxo de calor contra chapa molde de cobre. A liga foi avaliada quanto a sua microestrutura bruta de fusão e suas respectivas correlações com os parâmetros térmicos (velocidade da frente eutética -VE e taxa de resfriamento eutética -?E) e propriedades mecânicas. Os resultados mostram que a morfologia microestrutural predominante é composta por células ricas em estanho (β-Sn) circundadas por mistura eutética Sn+intermetálico tipo NiSn. Uma transição microestrutural foi observada entre as posições 15mm (?E=1,7°C/s) e 30mm (?E=1,1°C/s), de célula regular (CR)?célula tipo placa (CTP). Notou-se ainda a presença de intermetálicos primários NiSn distribuídos ao longo da matriz nas posições iniciais do lingote. Valores superiores de limite de resistência à tração (σu=26 MPa) e limite de escoamento (σy=21 MPa) foram encontrados para a posição 6mm a partir da base refrigerada do lingote, podendo estar relacionados com a estrutura celular mais refinada e também com a presença dos intermetálicos primários NiSn. O alongamento específico (?) comportou-se de maneira inversa, visto que as estruturas mais grosseiras (CTP) e a ausência de intermetálicos primários são responsáveis por facilitar a deformação plástica na estrutura da liga Sn-0,5%Ni, aumentando seu nível de ductilidade.

Oct 30, 2017

By W. Hermülheim, J. Brune

"This paper analyzes mine emergency management and rescue practices in German underground coal mines and compares them to those used in the United States. The German mining industry has developed these practices over more than 100 years, and they have successfully managed numerous fire, water inundation and ground control emergencies using these techniques. The authors interviewed German mine emergency professionals about rescue team and emergency operations. These operations were then analyzed to determine which of these German principles would be of interest to United States mine rescue teams. Implementing these programs into United States mine rescue and emergency operations was analyzed. INTRODUCTION Coal mining has become much safer industry than it has been in the past. Advances in safety and health regulations and company polices have improved working conditions for miners all over the world. Even with these advances there is still a need for continued attention to safety and health. It is also important for mine safety professionals to observe practices and procedures in other countries and cultures and learn what and how to apply this knowledge in their own systems. Coal mine rescue has been an integral part in improving coal mine safety. Mine rescue procedures have evolved with time, experience and technology development. Today, coal mine rescue teams are still needed and must be continually trained and prepared for any mine emergency. Although it is hoped that improved mine safety policies and practices will eliminate coal mine disasters in the future, accidents remind us that disasters can still happen today. In May 2014, Turkey experienced a severe coal mine disaster where 301 people were killed [G.Tuysuz, 2014]. Our industry must learn from these incidents, focusing on disaster prevention and making improvements in mine rescue operations. Mine rescue procedures differ from country to country due different regulatory environments and different historical evolution of emergency response. Sharing practices and procedures from one country to another enables learning from different experiences and cultural backgrounds. Sharing is also a way of preserving information, identifying and learning best practices."

Jan 1, 2015

By M. Bryson, S. Broom-Fendley, A. E. Brady, W. Dawes, G. Beer, N. Sehlotho, S. Al-Ali, F. Wall

The Songwe Hill Rare Earth Element (REE) Project in Malawi is a near surface carbonatite-hosted deposit with synchysite and apatite as the key REE bearing minerals. A strong focus has been placed on understanding the REE mineralogy of the Songwe Hill carbonatite as REE mineralogical characterization is a crucial component at all steps, ranging from exploration to production, in the development of REE deposits. Extensive mineralogical work has been completed at Camborne School of Mines (CSM), Natural History Museum (NHM) London, British Geological Survey (BGS), Nottingham, Aberystwyth University, Wales, Mintek, South Africa, and SGS Inc. Canada (SGS). The following analytical techniques were used: scanning electron microscopy (SEM), electron microprobe analysis (EMPA), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), and QEMSCAN®. The detailed studies have demonstrated that while synchysite is light-REE enriched as expected, apatite, abundant in all stages of carbonatite emplacement at Songwe, is anomalously enriched in mid- to heavy-REE relative to apatite in other carbonatite deposits. The distribution of REE within synchysite and apatite at Songwe has had important implications for the direction of the metallurgical work with respect to the behaviour of light and heavy REE through the flotation and hydrometallurgical stages of the flow sheet.

Jan 1, 2014

By R. H. Storch, D. C. Holt

During reconnaissance investigations of more than 300 stream areas in Idaho to determine the potential value of ilmenite in black - sand placer deposits 46 deposits were explored by churn drilling , trenching , test pitting , or shafting . The component mineral content and total black - sand content were determined for more than 8,690 reconnaissance and exploration samples . Data compiled during the investigation indicate a good potential for large , low- grade deposits containing ilmenite , monazite , columbite , euxenite , uranothorite , and other radioactive black minerals and accessory black - sand minerals . The data also indicate most deposits will be economic only if several component minerals can be recovered as coproducts .

Jan 1, 1963

By A Deakin

It has been almost a decade since the release of the International Council of Mining and Metals (ICMM) Health and Safety Critical Control Management: Good Practice Guide (2015a). During this time the ICMM member companies, along with many others across industry, have been busy designing, deploying and enhancing their own critical control management (CCM) programs. So, what have we learnt? This paper discusses the scope, application and learnings from the implementation of CCM within the mining industry. What’s going well? What are the common challenges? What are the opportunities to strengthen the approach? What are the threats to successful implementation? The paper draws on the author’s experience as one of the key contributors to the development of the CCM Good Practice Guide and an adviser to many mining companies, including six of the ICMM members. The paper focuses on the practical (operational) application of CCM and the cycle of identifying, defining, implementing, verifying and improving critical controls at the frontline. The paper also includes a discussion on the safety performance of the ICMM member companies over the past decade and provides a recommendation for how CCM can be incorporated into a more proactive model to measure safety performance. The paper concludes with practical recommendations that mining companies, regardless of their CCM maturity, can consider as they look ahead. They are supplemented by three additional recommendations for consideration at the industry level.

Apr 16, 2024

By Michael Tenenbaum

A REVIEW of process metallurgy of iron and steel during 1944 in many ways reflects the political and military developments of the year. Early in 1944 the tremendous wartime emergency expansion program was virtually completed and the industry directed its efforts to maintaining maximum production wherever needed. The vigorous production programs inaugurated to support the Normandy invasions did not persist as Allied armies approached Germany. General public apathy which developed with the prospect of an early ending of the European fighting was reflected in a general relaxation in armament programs. Toward the end of the year, as the prospect of a prolonged war became real, the entire program revived considerably and the need for steel became acute. Between January 1940 and October 1944 more than 12,400,000 tons had been added to the nation's steelmaking capacities, and over 12,700,000 tons added to the blast-furnace facilities. The total cost of this enormous program was more than two billion dollars. By July 1, 1944, total steelmaking capacity had exceeded 94,000,000 tons, with blast-furnace capacity rated at 68,400,000. Annual steel production, which was 88,900,000 tons in 1943, increased slightly during the past year and was estimated at 89,500,000. Production of pig iron also increased somewhat from 61,800,000 tons in 1943 to an estimated output of 62,500,000 in 1944. This review deals with a few of the numerous factors involved in maintaining the wartime iron and steel program at the level necessary to accomplish this enormous output.

Jan 1, 1945

By P. D. Kondos, J. R. Goode

Given the global inventory of low grade and refractory gold deposits, processes that could turn these challenged deposits into mines are of considerable interest. Such gold deposits have low value and potentially high operating costs and so they pose special challenges for the mining engineer and metallurgist. Conventionally, refractory gold ores have been processed by whole ore pressure oxidation and roasting, or flotation followed by roasting, pressure oxidation or bio-oxidation of the concentrate. Halide-based processes have recently been developed that might be applied to concentrates. Low grade refractory gold ores have been processed using heap bio-oxidation followed by cyanide heap leaching or milling. Other processes are emerging. Barrick has completed an inventory of emerging technologies (1). A summary of the current status of these developments will be presented with the view that, with additional development, some of these technologies or a combination thereof may unlock the value of these deposits.

Jan 1, 2005

By Chee Theng

"Keep calm and carry on mining. That has long been the conventional wisdom in the mining industry, a largely cyclical one that has weathered roller-coaster booms and busts. But in the years from 2002 to 2016, an unprecedented steep rise in commodities prices that lasted a decade and then took a sharp turn downward had made it hard for gold and silver miners to stay the course.“The last 15 years highlighted some of the structural and inherent challenges that our industry has, from product price uncertainty to long lead times to the capital intensity of our business,” said Mitchell Krebs, president and chief executive officer of Coeur Mining, who was the luncheon speaker at the American Exploration & Mining Association’s 122nd Annual Meeting held Dec. 5-9, 2016, in Reno, NV.Looking back, Krebs said, “We were given this enormous gift of a commodities super cycle, and the industry kind of blew the opportunity.” While gold prices rose 319 percent and silver prices rose more than 200 percent over the 2002 to 2016 period, the XAU index of 30 gold and silver mining companies’ stock prices went up by only 20 percent.Entering 2016, precious-metals prices have made a comeback, with gold rallying strongly from a six-year low at the start of the year. This time, the industry is ready. Companies are leaner and meaner, with lower costs, reduced debt and an increased focus on higher grades and quality ounces. Although opportunities were missed in the past, the industry has got its act together and is now well positioned to take advantage of a price upswing and even to show profits when prices fall, as they did in August 2016, pushed down by a strong dollar."

Feb 1, 2017

By Paul M. Tyler

NOW that the dust of World War II has settled and we and our allies are faced with extravagant losses of men, money, and materials, virtually the only hope that the United States and Britain have in the way of reparations lies in the capture of industrial, technical, and scientific secrets. Even during the war American and British scientists and technicians gained access to German factories, questioned German personnel, studied German documents, and endeavored generally to keep pace with new discoveries in science, industrial technology, and process development. Under various agencies this work continued for two years after the war. Altogether at least 600 American scientists and industrialists have gone to Germany and brought back reports and several times as many British, Canadian, and. Australian investigators have been similarly engaged under co-operative arrangements designed to assure the maximum of coverage with a minimum duplication of effort. As a result of these investigations and document studies, about 500 or 600 reports have been prepared on metallurgical and allied subjects. Those by American authors or joint teams have been listed in the annotated Bibliography of Scientific and Industrial Reports, issued by the Office of Technical Services in the U. S. Department of Commerce. Many of the British reports are also available in this country through the same office or through a British representative in New York. Since it was my duty to read most of these reports for

Jan 1, 1948

By A. K. Ratte, C. M. Brown

"IntroductionIn autogenous mills, grinding of the ore feed is accomplished by the direct action of the variously sized rocks making up the feed on each other and the mill interior. Size reduction is achieved without the addition of grinding media foreign to the mill feed, differing in this respect from rod, ball, and pebble milling. The term ""semi-autogenous"" has entered common usage in the industry to describe autogenous mills to which supplementary grinding ball additions are made to increase the rate at which size reduction of the mill feed occurs, beyond that achieved solely by the action of rock on rock. In a semi-autogenous grinding (SAG) mill, 50Jo to 10% of the mill volume may be occupied by grinding balls, whereas a range of 25% to 45% is more usual in ball milling.The comminution of mineral ores using ""conventional"" techniques has been described in previous papers. In conventional operations, size reduction of mined ore, and liberation of the valuable mineral content, is typically accomplished using flowsheets employing two to four stages of crushing. Crushing is followed by one to three stages of grinding and classification using various combinations of rod, ball, and pebble mills. This paper describes operations employing autogenous or semiautogenous grinding as the principal stage in the comminution process. Primary crusher discharge, or in some instances run of mine ore, is fed directly to an autogenous or semi-autogenous grinding circuit. Final product sizing may be accomplished in a single grinding stage, the mills operating in closed circuit with classification equipment, or in several stages using autogenous and semi-autogenous mills for primary grinding, and ball or pebble mills for secondary grinding. In several operations a portion of the primary mill discharge is crushed in an intermediate comminution step, these circuits being called autogenousball- crusher circuits (ABC). Many different flowsheets exist, but common and important to most are crushed ore stockpiles, reclaim feeder and mill feed conveyor systems, pumps, screens, and classifiers. Autogenous grinding is employed in both wet and dry processes, although today wet predominate."

Jan 1, 1989

By G. F. Olsen

ON superficial consideration a technical library might be considered a luxury to the business institution that possesses one. After all, public libraries and research institutions probably contain all the data that would be found in a private technical library, and able consultants are available both within and without a company. In all probability the technical men of a company have in their combined personal libraries sufficient information to answer most inquiries. Nevertheless, possession of such a department is of real economic benefit because of the time it saves its users, because it prevents expensive duplication of technical literature in a company, and lastly, but most important, be- cause it makes readily available a central storehouse of technical facts classified and indexed to meet the demands of the industry or industries concerned.

Jan 1, 1940

By Fabiane Leocádia da Silva

Cristais da família cristalográfica do sal de Tutton A2B(XO4)2.6H2O, A=K, NH4, Rb, Cs, Tl, B=Mg, Mn, Fe, Co, Ni, Cu, Zn, Cd, V, Cr, X=S e Se tem sido investigados por diversas técnicas experimentais com o objetivo de compreender suas propriedades físicas e potenciais aplicações tecnológicas. Investigações sobre o comportamento estrutural têm sido realizadas por difração de raios-x a fim de compreender suas propriedades estruturais, principalmente a distorção Jahn-Teller presentes nos cristais com cromo e cobre. Soluções sólidas destes sais na forma A2B'xB”(1-x)- (SO4)2.6H2O, têm sido relativamente pouco investigadas embora possam apresentar distorção Jahn-Teller. A estrutura dos cristais desta série à temperatura ambiente é monoclínica, grupo espacial P21/a com duas moléculas por célula unitária. Bons monocristais da série (NH4)2NixCu(1-x)(SO4)2.6H2O com 0

Aug 16, 2017

By N. O. Johnson

This is one of a series of-Information Circulars dealing with mining and milling methods and costs at mines in various districts in the United States. The Hog Mountain gold mining district is of the northern edge of Tallapoosa County, in the east central part of the State of Alabama. The district is equally close to Goodwater and to Alexander City, both stations on the main line of the Central of Georgia Railroad. From Alexander City the mine is reached by 13 miles of graded road, traveling in a northeast direction. In dry seasons the road is good; in wet weather it is bad but passable. Improvements are being made constantly on the road, so that in the near future the gravel road should be good under all weathered conditions.

Jan 1, 1936

By R. M. Santmyers

Of the sand and miscellaneous silica produced in the United States , ordinary sand and gravel are , of course , the most important, at least as regards volume of output . The building- construction industry absorbs approximately 75 per cent of the total value of all quartz and silica , as shown in Table 2 of Quartz and Silica, Part I, under "General summary . " Because of their unusual physical properties tripoli and diatomite find extremely wide uses in industry, and as the commercial deposits of these ninerals , especially tripoli , are scattered, large quantities enter into interstate commerce . Whereas ordinary sand and gravel are bulky commodities , these specialties have a fairly high unit value and hence can be transported relatively long distances .

Aug 1, 1931

By P. V. Fillo

This paper describes Mohave Mining and Milling Co. methods of mining and milling manganese ore in Arizona. It is one of a series of publications prepared by the Bureau of Mines on methods and costs in various mining districts in the United States. Production of manganese ore, as such, in Arizona began in 1915. Before this time manganiferous ores had been mined primarily for silver content and used as a smelter flux. From 1916 to 1918 approximately 69,000 long tons of manganese and mangsniferous ores were mined. After World War I production dropped to almost nothing until World War II, during which period more than 24,000 long tons were produced. A lull in mangonese mining occurred after World War II, having production rates of only a few hundred tons annually through 1952.

Jan 1, 1963

By Pedro Lilienfeld

This report describes a program to develop, design, fabricate and subject to environmental testing three prototype collection-sensing devices of an eventual mining-machine mounted automated monitor for the measurement of the respirable fraction of coal mine dust to determine both short-term as well as average mass concentrations over typical 8-hour shifts. The design of this instrument is based on collection by filtration and mass sensing by beta-radiation attenuation. The emphasis of this development program was to evolve a rugged, stable and reliable collection-detection head compatible with the environment to which An eventual monitor will be subjected. Laboratory testing of this prototype instrument was performed over a representative range of temperature, humidity, dust concentration and composition, shock and vibration. The results of this testing program indicated that the operation of the prototype version His compatible with these environmental conditions and that further development of this configuration into a field operational device is justified.

Jan 1, 1977

By J. R. Patts, A. B. Cecala, E. J. Haas

Exposure to respirable crystalline silica (RCS) remains a serious health hazard to the US mining workforce who are potentially exposed as various ore bodies are drilled, blasted, hauled by truck, crushed, screened, and transported to their destinations. The current Mine Safety and Health Administration (MSHA) permissible exposure limit (PEL) for RCS remains at approximately 100 μg/m3 , but it is noteworthy that the Occupational Safety and Health Administration (OSHA) has lowered its PEL to 50 μg/ m3 (with enforcement dates staggered through 2022 for various sectors), and the National Institute for Occupational Safety and Health (NIOSH) has held a 50 μg/m3 recommended standard since 1976. To examine a method for reducing RCS exposure using a NIOSH-developed video exposure monitoring (VEM) technology (referred to as Helmet-CAM), video and respirable dust concentration data were collected on eighty miners across seven unique mining sites. The data was then collated and partitioned using a thresholding scheme to determine exposures that were in excess of ten times the mean exposure for that worker. Focusing on these short duration, high magnitude exposures can provide insight to implement controls and interventions that can dramatically lower the employee’s overall average exposure. In 19 of the 80 cases analyzed, it was found that exposure could be significantly lowered by 20% or more by reducing exposures that occur during just 10 min of work per 8-hour shift. This approach provides a method to quickly analyze and determine which activities are creating the greatest health concerns. In most cases, once identified, focused control technologies or behavioral modifications can be applied to those tasks.

By B Besa

Australia is a world leader in the design and operation of mines accessed by the decline method. Literature indicates that a number of metalliferous underground mines using the decline system are also increasing steadily. This increase has generated a great deal of interest in underground haulage systems in future due to the huge costs involved in the development of declines. Studies have also shown that the current method of accessing orebodies by the conventional decline method has proved to be expensive, especially for narrow vein deposits. This is because decline development costs are influenced by mine planning and design parameters as well as available haulage systems that the mining engineer can choose from. The current access method suggests that more waste material is being extracted because of the size of decline openings adopted (5.5 mW and 5.5 mH). Also the conventional 1:7 decline gradient and turning radius of 20 m makes decline lengths, as well as the duration of development, excessively longer. This paper discusses results of a mine design case study with monorail technology as a method of accessing and developing the decline. The proposed system is economical, has high advance rates and offers a significant reduction in capital expenditure. The study compares costs, development metres and the duration of decline development using the monorail system with the conventional (truck haulage) access method. Results obtained indicate that the monorail technology has the potential to reduce the decline length by over 62.6 per cent and decline costs by 63 per cent for the case study. The monorail system also reduces the total capital development costs by 22 per cent for the same case study. Due to rapid development resulting from increased advance rates and the shorter decline length coupled with smaller decline openings, the time to access the deposit reduced by 71.8 per cent. This case study demonstrates that the economics of narrow vein deposits can be improved significantly by using the monorail system of decline development.

Jan 1, 2008

By S. H. Ash

No single factor in modern civilization has played a more important part in the lives of our people than mechanization in industry and to it civilization owes much of its progress. In no industry has mechanization met more opposition than in coal mining, where ?the introduction of mechanical equipment has been opposed on many fronts for economic and social reasons. The term 'mechanization? as used in this report refers to the application of machinery to cutting, loading, and transporting coal from the face to the mine cars. During 1933, 84.7 per cent of the underground production of the bitu-minous-coal mines of the United States (1) was cut by machines, while in Washington only 17.6 per cent was machine-cut. Information in this report has been obtained from personal observations and from operating officials in the Roslyn-Cle Elum coal fields, especially D. R. Swem, manager of coal operations, and Thomas Murphy, superintendent, of the Northwestern Improvement Company, to whom the author is indebted for assistance. INTRODUCTION Although Washington coal-mining problems relating co mining methods, ventilation, drainage, and preparation of coal have been discussed in many publications, little has been published on mechanization in this region, principally because it has not been accepted generally that mining machines, mechanical loaders, and conveyors are necessary or economically adaptable to the variable and steeply inclined coal beds of Washington. Production of coal in Washington reached its maximum in 1918, when 4,128,424 short tons were produced; from that year, the trend was downward until 1934, when production was 1,383,103 short tons, the lowest since 1898; for the past two years, production has risen steadily.

Jan 1, 1937

This paper discusses equipment replacement strategies and specifically addresses the upgrading of technologically superseded equipment. The process of equipment replacement evaluations is reviewed, and areas have been highlighted where currently accepted practice results in a bias towards retaining existing equipment longer than otherwise justified. The Discounted Average Cost Method is described and the advantages of the technique for this style of decision making discussed. Several key issues influencing the replacement evaluation are also presented together with examples from recent consulting work.

Jan 1, 1992