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By Prakash AJ, Singh PK, Dhar BB

Safety and stability of underground mine openings, coal pillars and water dams in the near vicinity of operating surface mines are endangered from excessive blast induced vibrations. This paper deals with the investigations carried out in four coal mines. Simultaneous measurements at equal distances from the source indicated higher level of vibration on the surface than those produced in the underground workings. The values of peak particle velocity (PPV) measured on coal pillars, body of water dam were lower than those measured on roof and junctions of the roadways. The parting of coal (3-4.5 m) between two sections vibrated with higher PPV compared to the roof of top section and floor of bottom section. In one case the influence of total charge fired in a round was significant in generation of vibration compared to the maximum charge/delay where monitoring was done vertically below the source.

Jan 1, 1995

By D. K. Deardorff, H. Kato

THE transformation temperature of hafnium from hcp to bcc is 1750° + 20 °C in contrast to previously published values by Duwez and fast2 which are believed inaccurate. The Bureau of Mines determined this value by measuring the temperatures at which a sudden decrease was observed in the electrical resistance of hafnium alloys containing up to 18 at. pct Zr, and then extrapolating the temperatures to 0 pct Zr. Duwez1 previously reported a transformation temperature of 1310°C, obtained by use of a rapid-cooling thermal-analysis technique. Later, Fast2 published a much higher value of 1950° 100°C based upon: a) his own determination of 1690°C for the beginning of the transformation range for hafnium containing 5.7 at. pct Zr, and b) his belief that lattice parameters reported3 for Duwez' hafnium indicated i contained 19 at. pct Zr and that the 1310°C value should be associated with that composition. Russell4 subsequently stated that Duwez and Fast probably were reporting their lattice parameters in different units and reassigned a value of 6.0 at. pct Zr to Duwez' hafnium. If this assumption were true, Duwez' hafnium was of approximately the same purity as Fast's, but his transformation value was considerably lower. The reason for this divergence is not known. Fast's value for hafnium containing 5.7 at. pct Zr agrees well with our data. McGeary5 determined a transformation value of 1660°C by metallographic examination of heat-treated specimens, but the zirconium content of his hafnium was not definitely established. The specimens used in this investigation were 1/8-in.-diam rods 6 1/2 in. long, fabricated by hot-swaging bars cut from arc-melted buttons. These buttons were melted from crystal bar hafnium and crystal bar zirconium. The chief impurity in the hafnium

Jan 1, 1960

By Brian E. Travis

Recent Developments in the utilization of polymer grid structures for Longwall Shield Recovery operations are discussed. Specifically: various Longwall screen designs and the numerous methods employed during installation. Also discussed is the role of polymer grid structures in head and tailgate mf and rib control and their role in controlling soft bottom often associated in shield recovery operations.

Jan 1, 1993

By R. H. Fernald

In 1900, as far as available records show, there were only two producer-gas power installations in the United States. In June, 1915, the number probably exceeded 1,000. Of this number, some 84.5 per cent comprised small plants using anthracite, and only about 15 per cent of the total number utilized bituminous coal and lignite. In addition to these, two plants used wood, and three or four used oil. In the main, however, the larger sized units are operating on bituminous coal and lignite. During the early years of these plants little success was anticipated from the use of bituminous coals and lignites, but in 1904 and 1905 it was fully demonstrated at the Government testing station at St. Louis that these fuels could be utilized to excellent advantage. However, although many producer-gas plants in daily operation are using bituminous coal and lignite, many power-plant men are still skeptical regarding the successful commercial use of these fuels.

Jan 1, 1916

By Anuradha Khetwal, Sandeep Khetwal, Andrea Panciera

The observation method is a design optimization approach for the drill and blast method in tunneling. This method includes first identifying the hazard scenarios through site investigation, formulating suitable solutions, obtaining feedback during construction, and finally using that data to optimize the design methods. This paper illustrates the application of the observational method for T-48, a railway tunnel project in the Himalayas. It is a 10.2 km long tunnel with a parallel escape tunnel and 26 cross passages. The use of observational methods in this project optimized the overall tunnel design and considerably saved the overall project cost.

Jun 23, 2024

By Francesco Chiappalone, Filippo Azzarà, Raffaele Aliberti, Daniele Nebbia, Lance Waddell

As part of the 3RPORT and NEBT Projects, 5-mile Combined Sewer Overflow Tunnels were excavated with a 19 ft diameter Slurry and 26 ft diameter EPB Tunnel Boring Machines. Due to the difficult geological and hydrogeological conditions, both tunnels were excavated maintaining a ground support pressure between 2 and 5.5 bar imposing significant challenges to the projects. The first part of the paper describes the general characteristics of both projects while the second part focuses on the challenges and technical details of the pressurized breakthroughs that took place in deep shafts excavated in urban environment as part of the projects.

Dec 1, 2022

By Adam C. Powell

A new Cahn-Hilliard phase field model of transport-limited electrochemistry describes phase boundary motion due to oxidation and reduction reactions at metal-electrolyte interfaces. Benchmarks demonstrating the accuracy of the method include open circuit voltage and closed circuit current in metallothermic reduction, and linear stability theory in metal electrolysis, including a new stability criterion for reduction of liquid metal from liquid electrolyte. The model is applied here to understanding cathode interface stability in titanium electrolysis e.g. in the SOM process developed with Uday Pal, and to structure evolution in subhalide reduction of titanium dichloride by magnesium developed by Toru Okabe. Potential for application to new fuel cell and battery systems is also discussed.

Jan 1, 2006

By Diessel C. F K, Ng N

The commonly used Stopes-Heerlen coal petrographic classification and nomenclature has over the years been subject to variable interpretations. This paper discusses the problem with specific reference to the inertinite maceral group. The effect of various interpretations of the Stopes-Heerlen system on maceral analysis is discussed and illustrated by means of comparative analyses conducted by a number of laboratories in Australia. An attempt is made to define the reflectance thresholds used by the authors to subdivide the inertinite group; the genetic and technological significance of these thresholds are compared. The difficulties of distinguishing structured and non-structured macerals of the inertinite group is discussed in terms of possible improvements to the present Stopes-Heerlen system by extending the classification to include transitional maceral types.

Jan 1, 1969

By Melvin D. Nelson

Executive Summary The future of coal as an important energy source in the 21st century will depend heavily on whether or not our industry is recognized for its performance. We have had a major role in powering our nation through the 20th century ... but many today do not understand that role nor do they know that 56% of our nation's electricity today comes from coal. Corporate communications, marketing, and public relations must be a high priority of our industry if we are to survive in the society of the 21st century as a viable energy option for powering our nation. The time to start is now. The place to start is locally. The way to strengthen local and regional efforts is to network on a regional and national level with associations who have the ability and the will to develop effective communications strategies. Introduction The Minnkota Power Systems is a regional association of 26 electrical suppliers. Serving more than 96,000 customers in a 34,500 square mile service area in Minnesota and North Dakota, the association includes 12 municipal utilities, 12 distribution cooperatives, a municipal power agency, and a generation and transmission cooperative. The Minnkota Power Systems generating capacity totals 613 megawatts, and 83% of it is fired by lignite coal. On an annual basis, 80% of our total energy is derived from coal. We are proud of our long association with the coal industry. Our pride shows in the very visible role that coal plays in our marketing and public relations efforts. In 1993, the Minnkota Power Systems had one of the lowest wholesale rates in the country, at 3.1 cents per kWh. Average residential rates were 5.8 cents per kWh. Minnkota Power Cooperative, One of the Minnkota Power Systems, is a generation and transmission cooperative headquartered in Grand Forks, North Dakota. Minnkota's Strategic Plan - Shaping the Future Minnkota recently completed a strategic planning process which is intended to give direction to our future and allow us to proactively influence the shape of that future. Minnkota's mission is to assist the associated systems in Improving the quality of life of their consumers by continuously improving the value of electric energy to the consumer. Our business focus is creating and keeping satisfied, long-term energy customers.

Jan 1, 1994

By Kung-Lee Wang

This report describes the linkage of all mining sectors with all other manufacturing, services, and final demand sectors of the U.S. economy. Besides being a basic data source, it provides a framework for aggregate economic impact analysis with respect to the mining industries. The framework is an open-static input-output model specifying 48 mining industries as classified in the Standard Industrial Classification Manual for all mining activities and 76 nonmining industries which collectively exhaust, all economic activities. The 124-sector model used in this report is an expansion of the preliminary 82-industry aggregation estimates made by the Department of Commerce. In the expanded model, 48 ruining industries are substituted for the original 6. The methodology used to ascertain the industry-by-industry procurement cost estimates and product ion flows necessary to the construction and expansion of the basic 82-sector model included personal interviews, case studies of specific mining activity analysis, and published and unpublished data from the Bureau of Mines and the Census of Mineral Industries, The end products of this study are two tables arranged to show the direct purchases necessary for each industry to support the level of economic activity and the total purchases generated in each industry throughout the economy by each $1 of aggregate economic demand in 1958. The tables may he used for economic impact studies and market analysis by firms engaged in or closely associated with the mining industries. Some illustrations of their usages are presented.

Jan 1, 1967

Despite limited discussion, Chemistry of Flotation is a good text and reference 1985 by M. C. Fuerstenau, J. D. Miller, and M. C. Kuhn Society of Mining Engineers Caller No. D Littleton, CO 80127 Softcover, $23.50 (member), $18.50 (student member), $28.50 (list) Review by Richard R. Klimpel Chemistry in Flotation, as stated by the authors, is intended as a textbook for students as well as a reference book for practicing flotation engineers. It covers subject matter related to surface phenomena; collectors and collector salts; natural floatability; the flotation of sulfide minerals, insoluble oxide and silicate minerals, semisoluble salts, and soluble salts; and slime coatings. There are no discussions in the book on practical plant implications of flotation chemistry, such as the influence of rate, particle size effects, dosage, flotation equipment, and methods of chemical addition. The book itself is small (only 177 pages), and, as published, is in an easy-to-handle soft cover. Once one accepts the intent of the authors, this book really does represent a very concise and convenient summary of the chemistry of flotation. It is, however, far from complete in its discussion of concepts and implications of data. Very often in the presentation, key prior knowledge (or at least subject matter awareness) not given in the book, is assumed. Thus, depending on one's familiarity with the specific subject matter, some sections can be easily followed while others could be tough going. Some of the discussion is so brief and terse on important subjects that unless the reader already realizes the meaning of the presentation, the conclusions to be drawn are not always clear. Therefore, if one is not expecting a self-contained primer on flotation chemistry, this book is very useful. To this end, the book is recommended to practitioners of flotation chemistry. The presentation of data in figures and tables is good. It helps considerably in the book achieving its conciseness. The authors certainly are qualified and knowledgeable in the subject matter - apparent in the style of presentation. In summary, this reviewer thoroughly enjoyed this book and will use it as a concise review of flotation chemistry. Richard R. Klimpel, member SME, is a scientist with Dow Chemical Co., Discovery Development, 1776 Building, M. E. Pruitt Research Center, Midland, MI 48640. International Symposium on Blast Furnace Ironmaking, 1985, The Indian Institute of Metals, The Tata Iron and Steel Co., Ltd., Jamshedpur 831007, India, 282 pp., papercover, no price given - Papers from this symposium held in Jamshedpur, India, include the following: determination of coal and coke quality; feed to blast furnaces; burden quality and blast furnace performance; operation of blast furnaces on charcoal; review of cast house slag granulation systems; developments in blast furnace engineering and control; process improvements in blast furnace ironmaking; coal injection into the blast furnace; and coke from stamp charged coal. Advances in Materials Technology for the Process Industries, 1985, edited by H.A. Huskins, National Association of Corrosion Engineers, P.O. Box 218340, Houston, TX 77218, 273 pp., softcover, $20-This book is the proceedings of a meeting held in Atlanta, GA in October 1984. It describes innovations in metallurgy, ceramics, glass, composites, and polymeric materials that impact the integrity and economics of operating systems. It covers biotechnical developments, improvements in membrane systems, or beneficiation processes, as well as developments in electrochemical controls, testing procedures, and surveillance techniques. A Reference Guide to Mining Legislation in Canada, 1985, by B. Barton, B. Roulston, and N. Strantz, The Canadian Institute of Resources Law, Room 430, Bio Sciences Building, The University of Calgary, Calgary, Alberta, Canada T2N 1N4, 120 pp., bound, $US28- This guide provides a ready means of finding how the different jurisdictions in Canada regulate mineral activity. It covers the rights required for exploration, development, and production of mineral metallics and industrial minerals. It does not cover placer mining, petroleum and natural gas, bituminuous sands, coal, or structural materials. Dictionary of Geological Terms, 1985, edited by Robert L. Bates and Julia A. Jackson, The American Geological Institute, 4220 King St., Alexandria, VA 22302, papercover, $7.95 plus $1 for postage - This third edition is for geoscience students, teachers, and rockhounds. It defines the core vocabulary of earth sciences, contains 8000 revised definitions, and includes 1000 new terms. It adds recent terms in plate tectonics, hydrology, and permafrost studies. Accurate definitions are given without technical jargon, cross-references are included, and commonly used abbreviations are provided. Processing and Utilization of High Sulfur Coals, 1985, edited by Yosry A. Attia, Elsevier Science Publishing Co. Inc., 52 Vanderbilt Ave., New York, NY 10017, 787 pp., bound, $142.50-These proceedings comprise the majority of the papers presented at the First International conference. Investigators there reported the latest discoveries, developments in commercial practice, and state-of-the-art reviews of scientific principles and applications of various technologies for handling, processing, and use of high sulfur coals. Sessions were held on: characterization of sulfur in coals; environmental problems and impact of high sulfur on coal use; selective mining and blending; coal desulfurization by physical and chemical cleaning techniques; handling of coal fines; sulfur capture during coal combustion; biological desulfurization of coal; and new applications for high sulfur coal. The Economics of Magnesium Metal, 1985, Roskill Information Services Ltd., 2 Clapham Road, London SW9 OJA England, 129 pp., 71 tables, appendices, bound, $750-Despite setbacks in some major magnesium markets in 1985, Roskill's latest forecast for the last half of this decade is for a 4% to 6% annual growth rate in demand. Growth for magnesium metal is expected in the motor industry for use as a possible substitute for aluminum. Some magnesium producers are altering their marketing strategies to cultivate this market. This study also includes a review of the worldwide magnesium industry, its end uses and consumption, and international trade and price trends.

Jan 7, 1986

By Janet E. Halliwell

In keeping with the traditions of the Science Council of Canada - an independent and forward looking agency that applies broad and multidisciplinary analyses to the various issues it examines the author indulges in a holistic approach to the integration of the environmental, scientific, economic, and cultural concerns. This paper will characterize the changing conditions which the mining industry is facing. It will then explore the changing expectations of society with respect to environmental sustainability and how those attitudes in turn, must influence the strategic directions and attitudes of the industry, and within that, the role of science and technology.

Jan 1, 1991

By Afrânio Márcio Costa

Placas lingotadas continuamente, não obstante atendam a requisitos como composição química, conteúdo de inclusões, aspectos macro e micrográficos, podem ser desclassificadas por falta de conformidade dimensional. Contrações térmicas, de solidificação e de transformações de fases são partes intrínsecas do processo e são afetadas por alterações na taxa de extração de energia da placa durante o processo. Este conjunto de contrações determina o Fator de Contração de operação, o qual é utilizado para determinar as dimensões do molde que irão resultar na largura especificada, onde o presente estudo determinará o fator de contração dos aços peritéticos. As variáveis identificadas que influenciam no fluxo de calor primário foram: frequência de oscilação, superaquecimento, velocidade de lingotamento e viscosidade do pó fluxante. Identificou-se que o resfriamento secundário e a conicidade utilizado no molde, também são critérios determinantes para obtenção de larguras especificadas. Assim sendo, uma equação de regressão foi desenvolvida para o Fator de Contração.

Aug 17, 2017

By Ivan F. Avery

DOMESTIC production of carbon black increased 4 percent in 1962 to 2,056 million pounds. Furnace black output was 8 percent, or 132 million pounds, above that in 1961 and accounted for 90 percent of total carbon black production. Channel black output continued to decline and was 55 million pounds less than in 1961. Carbon black shipments during the year totaled 2,082 million pounds and were 5 percent above those of 1961. About one-fifth of these shipments were exported; the balance were sold domestically. An increase of 180 million pounds in domestic sales was partially offset by a decline of 80 million pounds in exports. Total value of carbon black production in 1962 was $145 million. The average value per pound of 7.06 cents was 0.24 cent per pound less than in 1961. Producers' stocks declined 26 million pounds during the year.

Jan 1, 1963

By B. R. Neufeld, M. G. Heximer, S. J. Roach, W. G. Van Luven, D. G. Reynolds

"Teck Metals Ltd. operates an integrated zinc-lead complex at Trail, British Columbia, Canada. In the zinc plant, zinc concentrates are roasted to produce calcine, which is then processed in the leaching circuit for zinc recovery. Calcine is first dissolved at pH <2.0. This is followed by a precipitation stage using additional calcine that removes iron as a ferric hydroxide precipitate which is recycled to the lead operations. It is during this pH adjustment that impurities, notably arsenic, antimony and germanium, are co-precipitated with ferric hydroxide which is the primary removal phase for these elements. Recent processing conditions have resulted in lower iron inputs to the leaching circuit and this has resulted in insufficient co-precipitation of key impurities. This paper summarizes the influence of iron concentrations on impurity removal using laboratory and plant scale surveys, and emphasizes key specification limits for the primary iron removal circuit.INTRODUCTIONThe Sulphide Leach Plant (SLP) at Teck Metals Ltd., Trail Operations produces a zinc sulphate electrolyte from three different zinc bearing streams:1. Calcine, primarily containing zinc oxide, from the roasters2. Zinc electrolyte from the Oxide Leach Plant (OLP) is produced by leaching zinc oxide fume from the pyrometallurgical lead smelting operations3. Zinc slurry from the Zinc Pressure Leach (ZPL) autoclaveThe feed sources are blended and introduced to the iron removal process to precipitate iron in the form of a hydrolyzed iron precipitate which is recycled to the lead smelting operation. Along with iron, impurities, namely arsenic, antimony, germanium and silica, also co-precipitate; this process acts as the primary removal step for these elements. Following iron removal, the electrolyte is further processed in the zinc dust purification circuits. Cadmium and copper are removed in the cold stage circuit via zinc dust cementation, followed by cobalt cementation in the hot stage circuit."

Jan 1, 2016

By Afshin Sadri

Uma das principais razões para o reparo de altos-fornos é a perda do revestimento refratário, principalmente nas regiões da soleira e onde são feitos os furos de corrida. A operação intensa dos altos-fornos pode resultar em desgaste e deteorização extensiva do material refratário. Isto pode, então, afetar a continuidade das operações e a vida útil do forno. Novo-Lipetsk (NLMK) e a Hatch desenvolveram uma abordagem sistemática para monitorar a condição do revestimento da soleira dos altos-fornos usando Acousto Ultrasonic-Eco (AU-E), um sistema de ensaios não-destrutivos desenvolvido pela Hatch. Inspeções contínuas e periódicas dos altos-fornos revelaram áreas com deterioração acelerada do material refratário, formação extensa de “elefant foot” e acelerado desgaste do refratário, assim como fissuras e outras anomalias. Para prolongar a vida do forno, mantendo a intensidade de suas operações, algumas modificações, tais como a melhoria da qualidade do coque e da limpeza das placas de resfriamento e adição de óxido de titânio, entre outras medidas, foram recomendadas e aplicadas. Este trabalho demonstra como esforços coordenados entre a NLMK e a Hatch resultaram no prolongamento da vida útil de um alto-forno

Aug 17, 2017

Orange Free State Branch Minutes of a Committee Meeting held in the Boardroom of Western Holdings on Thursday, IIth October, 1973, at 5.00 p.m. Present Messrs E. T. Wilson (in the Chair), E. Dunstan, W. B. Evans, C. J. Isaac, C. Mostert, N. Shand, R. Williams, and G. Young.

Jan 2, 1974

By Walisson Silva Gomes

A injeção de carvão pulverizado pelas ventaneiras dos altos-fornos é um dos meios de redução de custos de produção do ferro gusa. Esta injeção deve ser de forma efetiva para evitar possíveis desperdícios de combustível. Esse trabalho teve como objetivo desenvolver uma metodologia de quantificação do teor de carbono na lama e no pó de coletor, gerados na limpeza de gás do alto-forno para auxiliar a avaliação da eficiência de queima do carvão injetado pelas ventaneiras e sua correlação com as variáveis de processo. Nenhuma norma especifica a quantificação de carbono na lama e no pó de coletor. Foram utilizadas duas técnicas de quantificação de carbono em carvão e coque utilizados na Companhia Siderúrgica Nacional, a Análise Imediata, baseadas na norma ASTM D 5142-09, e a Análise Elementar. Um estudo mais detalhado para investigar as possíveis interferências nesses métodos de análise, devido a diferença de resultados entre eles, foi utilizado Difração de Raio-X, associado ao método de Rietveld, e Analise Termogravimétrica de Calorimetria Exploratória Diferencial (TG-DSC). A partir dessas análises foi possível definir o melhor método para quantificação de carbono no pó de coletor e lama de alto-forno.

Aug 17, 2017

By J. A. Fellows, Earnshaw Cook, Howard S. Avery

HEAT-RESISTANT alloys of the higher nickel and chromium ranges have been empirically developed through the practical experience of the past two decades to a position of significant industrial importance. Few quantitative metallurgical data have been published, however, that could be related directly to engineering specifications and design. Inadequate information led to the inauguration, in 1934, of a research directed toward a better understanding of the properties and performance of these steels at temperatures between 1400° and 2000°F. Investigation was concentrated upon the 26 per cent Cr:12 per cent Ni type, which owes its extensive application to an excellent combination of economy, strength and surface stability at elevated temperatures. The requirements of the oil-refining industry have been prominent in influencing the scope and evolution of the program. Creep strength at the maximum allowable deformation ranges has been employed to evaluate the merits of these alloys. Permissible elongation rates vary from 1.0 per cent in one million hours for turbine blades to 1.o per cent in ten thousand hours for tube supports and heating-furnace equipment. Throughout this paper, the limiting creep stress (L.C.S.) for a given temperature has been defined as the stress that will produce a uniform elongation rate (stage II) of one per cent in ten thousand hours as extrapolated from rates per hour or tests of less than two thousand hours duration. Certain current specifications require a minimum L.C.S. of 1600 lb. per sq. in. at 1800°F., of 3600 lb. per sq. in. at 1400°F., and include a tensile acceptance test at room temperature, after aging for 24 hr. at 1400°F., as a measure of embrittlement in service. An elongation of 4 per cent is considered satisfactory for general use, while a minimum of 9 per cent is prescribed on occasion. Many differences of opinion concerning the properties and performance of these alloys appear to result from their sensitivity to unappreciated variations of chemical analyses which, for example, may change their L.C.S. from 3500 to 350 lb. per sq. in. at 1800°F. Within broad chemical limits, it is possible to balance the six or more important elements present to attain desirable properties with a number of different combinations. One method for adjusting the composition has been described under the sponsorship of the Alloy Casting Institute,1 in which, by maintaining a substantially austenitic* alloy, optimum creep strength and minimum tendency to embrittle after aging are expected. Unless, however, the limits are undesirably dose, it has not been possible to ensure a moderate range of strength and of ductility by any chemical specification alone. There is a definite need

Jan 1, 1942

By Subhas G. Malghan

Feldspathic deposits occur widely throughout the United States, but North Carolina, California, Connecticut, and South Carolina accounted for over 80% of the total domestic feldspar output for the year 1973.1 Pegmatites and granites constitute the major feldspar reserves of the United States, 2 and in addition, feldspar is produced as a byproduct by firms whose major products are spodumene and mica. 3 Feldspar flotation is practiced in the United States, Mexico, Finland, Norway, West Germany, Japan, and the USSR. According to the US Bureau of Mines estimates, the production of feldspar in the United States and rest of the world were 704,000 and 2,514,000 t, respectively. Feldspar is principally used as a flux in making glass, pottery, porcelain, enamel, tile, and other ceramic products. In recent years, the domestic feldspar industry is faced with a number of problems. As a result of increased cost of energy and the introduction in 1972 of new legislative programs relating to air, water, and noise pollution, land-use restrictions, and mined-land rehabilitation, the production costs have increased. Apart from the increased cost of operation, an operational problem exists with the feldspar producers in North Carolina, especially those in the Spruce Pine area. This problem is concerned with the use of hydrofluoric acid in the feldspar flotation. Feldspar producers in Spruce Pine, NC, have been discharging process waste water into the North Toe River. The mill waste water contains active fluoride ions. Fluoride in excessive concentrations is undesirable in waters used for drinking. It is stated that water containing 0.9-1.0 ppm fluoride will seldom cause mottled enamel on children&apos;s teeth; and for adults, concentrations less than 3-4 are not likely to cause endemic cumulative fluorosis and skeletal effect. Although the literature on this subject is rather confusing and inconclusive, the inference that concentrations over 4 ppm may affect bone structure is clear. According to the recent Federal Register,4 maximum fluoride level of 1.4 ppm at 79°-98°F is considered to be adequate and safe for the protection of health of the consumers. The EPA and state environmental agencies have accelerated their drive to reduce water pollution on a faster schedule. By 1977, the EPA specifications for maximum contaminant level of fluoride ions in the discharge waters of feldspar milling operatins is expected to be reduced to 2.0 ppm. The other problems of using hydrofluoric acid are the following: toxicity, hazards of handling and storage, and high cost as compared to other inorganic acids (almost 16 times the cost of sulfuric acid). In order to reduce fluoride levels in mill discharge waters, mining companies have taken the following steps: I) Recirculating a part of their mill water. Even though recirculation of mill water seems to be a novel method of reducing fluoride contamination of the discharge water, there are certain operational and handling problems. 2) Conducting research on the treatment of fluorides in mill waste water. The technology of treatment of fluoride ions has received considerable interest in the recent years. A recent research report5 estimates that the cost of fluoride ion removal to meet the present specifications in the feldspar industry is approximately $0.25/t of ore processed, and about $0.50/t of feldspar produced. At the request of the feldspar producing industries in North Carolina, the North Carolina State University (NCSU) Minerals Research Laboratory has taken up a research program directed towards overcoming the fluoride ion pollution problem. After a close study of the operational, technical, and economic aspects of feldspar flotation, it was decided to attempt to replace the conventional hydrofluoric acid process. Conventional Feldspar Flotatin Using Hydrofluoric Acid Since the inception of the feldspar flotation process using hydrofluoric acid by O&apos;Meara2,6 the process has achieved a great commercial success. In the conventional flotation separation of feldspar-quartz, hydrofluoric acid is used to suppress quartz and activate feldspar, and a long chain amine salt (acetate or chloride) is used as a collector. The bulk of amine collectors used in current feldspar operations are applied as the water-soluble acetates of the free-base amines. These products are pastes or waxy solids which are available in a range of acetic acid neutralization levels generally 50 to 100% neutralized. In spite of the problems mentioned in connection with the use of hydrofluoric acid, this process is extremely stable with respect to changes in the process variables. With the exception of a few operations, alaskite and pegmatite are the major sources of feldspar.7 In the flotation treatment of a pegmatite that contains iron-bearing minerals (heavy minerals), mica, feldspar, and silica, a logical order of removal presents itself considering the following:8 1) Mica is readily floated by an amine collector in a pulp pH 3.5. Some iron-bearing minerals will usually respond to amine collector in acid circuit with the mica concentrate. 2) Since iron minerals tend to occur invariably in the feldspar concentrate, it is desirable to remove most of these prior to feldspar flotation. A fatty acid or a petroleum sulfonate collector used in this flotation step in acid circuit will float iron-bearing minerals. 3) Using hydrofluoric acid to maintain pH of 2.5, an amine collector employed in a final step will float feldspar away from silica, usually leaving the latter in the tailing as a high-grade silica concentrate. The problems connected with the flotation separation of feldspar-quartz arise due to the similarities in their chemical structure. Therefore, any reagent system that is likely to succeed in feldspar-quartz separation should have adsorption affinity towards one of the minerals and depression effect towards the other mineral.

Jan 1, 1979