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By W. M. Pytel

A simplified two-dimensional model to analyze time-dependent load distribution and surface subsidence associated with longwall mining geometries is described. The model is based on the theory of beams resting on inelastic foundations and includes visco-elastic behavior of immediate floor strata, non-linear behavior of coal pillars, elastic behavior of face supports, and visco-elastic behavior of the overburden strata. The relative importance of the different variables affecting the performance of longwall mining geometries from ground control point of view is also analyzed. The model has been validated for field observations from one Illinois longwall mine.

Jan 1, 1986

By P. L. De Bruyn

[According to the Young equation, SG = SL + Coso, the equilibrium contact angle depends on the values of the three interfacial tensions involved. A solute promotes wetting, i. e. a decrease of contact angle if it decreases.LG and/or YSL or if it increases SG. Dewetting, the important step in flotation is, promoted if the solute increases y and/or SL or decreases. Most solutes used for wetting or dewetting are, positively adsorbed at all interfaces involved and consequently according to the Gibbs equation lower the interfacial tensions. Wetting is therefore expected to occur if LG and SL are more affected by the solute than SG. Dewetting on the other, hand demands a greater decrease of SG than that of SL (and of LG). See P. L. de Bruyn, J. Th. G. Overbeek and B. Schuhmann, Jr., Mining Engineering (1954) P. 519.]

Jan 1, 1960

By A. Tobey Yu

The smelter is the heart of a copper producing operation. Its principal function is to reduce and convert raw copper concentrates and/or leach plant precipitates into blister copper before it is refined. In addition to concentrates and precipitates, typical feed to a smelter also encompasses matte chips, flue dust, flux and lime. By nature, the characteristics of these materials are extremely variable, ranging from sub-micron to lumps, from slurry to dust, from abrasive to corrosive and free-flowing to adhesive. Furthermore, as a result of geological formation, most of the world's open pit copper mines are located in a semi-arid zone, where precipitation is minimal. This particular climate compounds the problem of handling these materials.

Jan 1, 1976

By Robert J. Hite, James P. Searls, Sherilyn C. Williams-Stroud

Potash is a generic term that includes potassium chloride, potassium magnesium sulfate, potassium sulfate, potassium nitrate, and sodium-potassium nitrate mixtures. In the ceramics industry, potash is also used to refer to potassium oxide. Potash, primarily in the form of potassium carbonate, was the first industrial mineral produced in the United States, and the first US patent issued was for an apparatus and process developed in 1790 for its production (Paynter, 1990). Prior to the 1860s, potash was primarily sold as an impure form of potassium carbonate produced by burning hard- wood trees and leaching the potassium salts from the ashes. The major early uses of potash include soap and glass making, dyeing fabrics, baking, and saltpeter for gunpowder. In 1859, the development of a purification process to remove the sodium and magnesium chlorides was developed for the carnallite found at Stassfurt, Germany, and mined potash became available. With the appearance of mined potash and the earlier (1840) discovery in Germany by Justus von Liebig that potash was a nutrient for crops, potash started to be used for high valued crops such as cotton and vegetables. The German potash companies quickly developed a manufacturing process for producing potassium sulfate for tobacco fertilization. German potash supplied nearly all American needs until the embargo of the First World War when imports from Germany were interrupted (Bateman, 1918). With the discovery of potash deposits in New Mexico in 1931, the United States became self-sufficient in potash. In 1962, the United States began importing potash from Canada, and two years later domestic apparent consumption began to exceed domestic production. Along with nitrogen and phosphorus, potassium is one of the three essential plant nutrients, the "K" of NPK terminology. As a result, 95% of potash production is used as plant fertilizer. In all plants, inadequate potassium diminishes growth, causes increased disease, stalk and stem breakage, and susceptibility to other stress conditions. Plants take up large quantities of potassium from the soil, and potash fertilization replaces this loss so that each new crop can be grown with the same vigor and productivity as the previous year's crop. The potassium depletion of the soil from growing repeated cotton and tobacco crops is well known in the history of southern agriculture in America. George Washington was known to have studied alternative crops that could be grown on soil that had been depleted by repeated tobacco crops. Most of the remaining 5% of potash consumption is by the chemical industry, as potassium hydroxide to produce soaps and detergents, glass and ceramic products, dyes, explosives, alkaline batteries, and medicines. Potash as chemical is used in oil field drilling mud, the aluminum recycling industry, and the electroplating industry. Additional minor uses for potassium chloride include water softener regeneration, sidewalk deicing, and salt substitution for human consumption. Potash is used in the food industry as potassium phosphate, and in production of glass products as potassium carbonate or nitrate. GEOLOGY Potassium is the seventh most abundant element in the earth's crust and the sixth most abundant element in seawater. It is found in silicate minerals of igneous, metamorphic, and sedimentary rocks and is also a major constituent of many surface and subsurface brines. The majority of world potash resources are found in subsurface bedded salt deposits which yield high grade, large tonnage ore bodies and are amenable to low cost mining and beneficiation. Because of the relatively high solubility of potassium minerals, potash from salt deposits is ideal for use as fertilizers. Some potash production is from evaporation of naturally occurring brines, but the vast majority of current domestic and international production is from bedded salt deposits. Sylvite, carnallite, kainite, and langbeinite are some of the more important potassium minerals (Table 1). Sylvinite, a mixture of KC1 and NaCl is the highest grade potash ore. Carnallite can be considered a potash ore when removal of magnesium chloride is included in the beneficiation, but it can also be considered a contaminant when mining for sylvite. Potassium sulfate and potassium nitrate are typically manufactured products. Potassium sulfate is produced from mined minerals through conversion processes in Italy, Germany, and Carlsbad, NM, and from brines in southern California and at the Great Salt Lake in Utah. Natural deposits of potassium nitrate occur only in small amounts in Chile. The majority of potash-bearing bedded salt deposits are believed to have originated from the evaporation of seawater or mixtures of seawater and other brines in restricted marine basins (Schmalz, 1969). The reflux depositional model for evaporite deposition was first described in the literature in 1888 by Ochsenius. A shallow bar, or sill, across the mouth of a basin lets in a restricted flow of seawater which evaporates into a salt-precipitating brine (Fig. 1). The density of the brine at the distal end increases with increased salinity, sinks to the bottom, and sets up a reflux current of higher density brine back toward the ocean. The sill, which restricts the inflow of seawater, allows inhibited flow of evaporation-concentrated brines back to the ocean. The least soluble salts are precipitated nearer the sill, and the most soluble components come out of solution in the deeper parts of the basin. The result is a lateral facies change in a tabular-shaped deposit that is due to the salinity gradients in the brine (Fig. 2A). The asymmetrical facies distribution of the Paradox Formation (Middle Pennsylvanian) Utah (Hite, 1970), the Prairie Formation (Middle Devonian) in Saskatchewan (Holter, 1972), and the Salado Formation (Upper Permian) in New Mexico (Lowenstein, 1988), might prompt explanation by such a model. Other deposits, such as the Salina Formation (Upper Silurian) in Michigan (Matthews and Egleson, 1974), show a facies distribution that could be described as a bull's eye pattern. Although some small subbasins of high grade sylvite are found near the margins, the potash is generally located in a central part of the basin surrounded by successively less soluble facies (Fig. 2B). The sparse

Jan 1, 1994

By Angela K. Braden

Igneous rock exposures occupy only a minor portion of surface area (<18 mi2) in Arkansas, and are divided into two major groups: nepheline syenite (7 mi2) and syenite complexes (8 mi2), with various dikes and sills representing the remaining surface exposures. The syenite complexes have been the sites of major vanadium and minor titanium production during the past 50 years. Nepheline syenite exposures were important in the early production of locally used building stone; however, aggregate and roofing granules have now become the principal market for the production of nepheline syenite in Arkansas. Nepheline syenite intruded into a sequence of Paleozoic sedimentary rocks in Arkansas and is exposed in two areas: in Saline County near the town of Bauxite, and in Pulaski County at Granite Mountain, just southeast of Little Rock. Although the central Arkansas region had been investigated thoroughly for bauxite by the early 1950s, the nepheline syenite resources of the region have yet to be evaluated systematically by the state. Arkansas nepheline syenite was evaluated for its ceramic uses in 1952. Some recent industry interest has revolved around its potential use as a sand-blast abrasive. The largest exposed areas of nepheline syenite, located at Granite Mountain, currently are being mined by the Minnesota Mining & Manufacturing Company (3M) and McGeorge Contracting (Granite Mountain Quarry). 3M has been in operation since 1947 and mainly produces roofing granules. A fine powder produced by 3M during crushing that is marketed under the name Donnafill? recently has seen use as filler in self-compacting confined construction and as an additive (frit) in common brick. Since the early 1960s, Granite Mountain Quarries has produced a variety of aggregates, ranging from riprap to industrial sand, and recently constructed a computerized hot-mix-asphalt production facility. Approximately 4.5 million tons and 1.2 million tons of syenite were produced from Granite Mountain and 3M, respectively, during 1979. No production values are available after this date; however, combined production from both quarries is estimated to be at least 6 million tons annually.

Jan 1, 1999

By Heinz Hofmann

In order to drive tunnels with low overburden in town regions, it is necessary to give a quantitative prognosis for the deformation of the underground as well as of the tunnel-lining and of its stability. These problems and their solutions are illustrated by the works for a two-track-railway-tunnel in Bochum (Ruhrdistrict). In this case the most important problems consisted in passing below buildings in a vertical distance to the fundamentals of only 3.20 m and a railway earthdam with rapid train traffic in a distance of 4 m under the dam. The results of measurements from other comparable tunnels and finite-element-computations were used to prognose the settlements on the surface and in the ground, their distributions and their development in time. To obtain these values at the site, a special system of tunnel driving was executed. The tunnel was excavated with the newest type of tunneling-machine from DEMAG, cutting an inclined front, immediately followed by a special temporary support of shotcrete and inclined steel-ribs. By using theoretical and empirical methods to assess the behavior of the tunnel and underground and by executing an optimal driving system in technical as well as economical aspects, the expected behavior, expressed in quantitative values, was almost equivalent to those received by control measurements.

Jan 1, 1974

By Jeffrey P. Chanton

A specialized Pore-Fluid Array sampler (PFA) was designed to collect and store pore-fluids to monitor temporal changes of ions and gases in gas hydrate bearing sediments. We tested the hypothesis that pore-fluid chemistry records hydrate formation or decomposition events and reflects local seismic activity. The PFA is a seafloor probe that consists of an interchangeable instrument package that houses OsmoSamplers, long-term pore-fluid samplers; a specialized low-dead volume fluid coupler; and eight sample ports along a 10-meter sediment probe shaft. The PFA was deployed at Mississippi Canyon 118, a Gulf of Mexico hydrate site. A 160-day record was acquired from the overlying water (OLW) and 1.3 meters below seafloor (mbsf). Fluids were measured for dissolved chloride, sulfate, and methane concentrations and dissolved inorganic carbon and methane stable carbon and deuterium isotope ratios. Chloride and sulfate did not change significantly over time, suggesting the absence of gas hydrate formation or decomposition events. Over the temporal record, methane concentrations averaged 4 mM at 1.3 mbsf and was thermogenic in origin (d13C-CH4 = -32.4±3.4?). The timing of an anomalous 14 mM methane spike coincided with a nearby earthquake (Mw=5.8), consistent with the hypothesis that pore-fluid chemistry reflects seismic events. Keywords: Osmosampler, gas hydrate, methane, stable isotopes

Jan 1, 2008

By M. Jack Snyder

The problem of effective utilization of fly ash has been given wide attention for a number of years. Although the effort devoted to the problem has led to some applications of demonstrated usefulness, the full utilization of fly ash has been held back by lack of concerted research and development activity, by lack of effective dissemination to potential users of fly ash of the knowledge that is available from laboratory and field studies, and by the obvious variability of the product. Because of the variability in fly ash from one power plant to another and from time-to-time in the same plant, specifications have been set up defining compositional or property limits within which a fly ash must fall to be used in certain applications. This paper discusses the bases for such specifications and examines them in the light of recent research on the characterization of fly ash. Other limitations and restrictions on the use of fly ash and what is being done to overcome them are also discussed.

Jan 1, 1968

By F. J. Chernosky

In the past, a number of papers have been written on the use of various reagents as coal flotation frothers. For the most part, these papers have attempted to correlate the intrinsic chemical and physical properties of the reagents or reagent groups to the floatability of various fine coals. Because of the type or nature of evaluations made, chemically pure reagents were normally used. Generally, these reagents are unavailable in commercial quantities. Therefore, the results obtained with these reagents were usually limited in usefulness to the plant operator or metallurgist. This paper presents the results of a study in which commercially available forms of various reagents were used as flotation frothers. Flotation procedures which would conform in general to those employed in a large number of commercial coal flotation plants were utilized. The objective of the test was to compare these reagents on yield-selectivity-cost basis, that is, (1) the yields obtained, (2) the ash levels obtained, and (3) the reagent cost relating to these results.

Jan 1, 1962

By David H. Carrillo

HYL has developed a sticking tendency test which accurately predicts behavior of iron oxide feedstocks in the HYL III process. Test results together with pilot plant experimentation and commercial scale demonstrations permit the conclusion that lump ores will not agglomerate at 960°C (1233 K) in an HYL III Plant. Pellets may also be processed without agglomeration at 960°C (1233K) with the addition of no more than 5 percent lump ore. Using the HYL III process, the ironmaker can exploit feedstock market conditions without sacrificing plant productivity or energy efficiency.

Jan 1, 1981

By Stephen Semeniuk

Discussion by Stephen Semeniuk Discussion As a valuator and SME member, I view Ross D. Lawrence&apos;s position as based on unproven and faulty assumptions made with regard to the pragmatic evidence presented in his paper. Moreover, his call for the inclusion of all mineral resources in discounted cash flow valuations is redundant, if not irrelevant, as there are procedures that already take all classes of mineralization into consideration for valuation purposes. In my experience as a valuator, I find that Canadian securities regulators are more than accommodating in allowing any valuations of mineral properties to be based on cash flow calculations. In other business areas, the same regulators usually reject discounted cash flow valuations of projects or businesses with no operating history. Instead, the regulators prefer valuations to be based on other transactions tested in the marketplace. Valuations based on actual market transactions are less subjective than discounted cash flow calculations and/or the capitalization of arbitrary, untested or undemonstrated earnings projections. In the mining and minerals sector, such projections may be made by persons not qualified to make such projections. In support of this statement, I direct readers to the article "Valuation of mineral properties which do not contain exploitable reserves" by Lionel C. Kilburn, which appeared in the August 1990 issue of the CIM Bulletin. To quote from the article: "Value of a mineral property depends basically upon metal prices, recoverable grades, mining and metallurgical practices, commodity supply and demand, and political-economic conditions, all of which vary with time. Five fields of expertise influence the value of a mineral property: •geological engineering, •commodity markets, •financial markets, •stock markets and •mineral property markets. The skills of geologists and engineers properly apply to the first field of expertise. Knowledge and consideration of the other four fields is important, but such advice is more properly sought from marketing experts, economists and stockbrokers." Securities regulators have created no hardship for valuators by excluding unsubstantiated resources in discounted cash flow valuations. In the field of engineering, best design practices apply. A margin of safety is built into the design criteria for any new equipment or structure that will exceed normally expected load levels and stresses, even though such considerations imply higher front end costs. In accounting, the comparable operating principle is conservatism. It explains why, for balancesheet presentation purposes, inventory is stated at cost or market, whichever is the lowest value. Similarly, when the engineering or geoscience-based valuator plays in the field of finance, the rules of accounting and applied economics apply. Regulators in their skepticism of income-based valuations are in tune with similar views already expressed in mining literature. To quote H. Van Tingley, in Mining Magazine, July 1996: "... the DCF method has inherent dangers when applied to undeveloped resources. Firstly, it presents an often-undeserved aura of accuracy. A DCF value is no more accurate than the least accurate of the assumptions incorporated into the calculation - and assumptions

Jan 1, 2003

By William Lodding

That grinding may change a crystalline material both in a physical and in a chemical sense has been shown by a number of authors in recent years. Thus Mackenzie (1) and Bartha (2) reported the effects of careful grinding on muscovite, quartz, gypsum, dolomite, etc. Increase in specific surface produced by grinding implies increase in total energy of a system. Newly produced surfaces are chemically more reactive; dislocations may be introduced during grinding, and existing strain may be released by the same process, as shown by Holt et el. (3) All these changes are easily detected by thermal analysis, but it is not easy to separate the multiplicity of effects registered and to arrive at quantitative interpretations. This paper is an attempt to analyze by the use of thermal analysis some effects produced in grinding. In differential thermal analysis (DTA) one measures all thermal changes occurring in a substance during heating or cooling. Chemical changes, such as decompositions, synthesis, oxidation, reduction, etc., and physical changes such as phase transformations, changes in specific surface and in thermal conductivity, strain release, etc. By thermo gradmetric analysis (TGA) on the other hand only chemical changes involving weight loss or gain are recorded. Similarly gas evolution analysis (GEA) will register only reactions involving gas evolution, including water vapor, and oxidation-reduction. By performing two or all three of these thermal methods of thermal analysis simultaneously and on the same specimen one can separate the different effects registered and by difference evaluate their magnitude.

Jan 1, 1966

By W. L. Chen

In the United States hydraulic cyclones have been used for thickening, classification and cleaning in coal preparation plants for many years. The cleaning cyclones presently in use are based on using a "heavy medium", such as a fine magnetite and water pulp. The latest addition to cleaning cyclones is the one which uses ?water only?, or simply called "Hydrocyclone". Just as was the heavy medium cyclone, the hydrocyclones were originated in the Netherlands (1, 2). Plants using hydrocyclones were built in Europe (3) and test plants were erected in Canada (4, 5, 6) and India (7). Roberts and Schaefer Company has built four plants using hydrocyclone circuits. One additional plant is in the process of construction.

Jan 1, 1965

By Bond. F. C.

Introduction Although autogenous grinding applications date back to the early years of mineral processing when tumbling-type mills were first used, there has been a renewed interest in this type of grinding over the past few decades. A review of the historical aspects of autogenous grinding is provided which follows the development of the various types of mills and processes. Wet and dry grinding operations using either autogenous or semiautogenous mills, including the Aerofall mill, are described. Em¬phasis has been placed on the test work required to evaluate the feasibility of using autogenous or semiautogenous grinding for a spe¬cific application. The factors which must be considered to establish the appropriate design criteria for these types of grinding circuits are discussed in detail. Successful application of these grinding circuits results from a thorough test program, a careful analysis of the test results, and a practical engineering approach to the design of the process flowsheet and milling equipment. Certain pebble milling applications, where the pebbles consist of the ore or rock itself, can be classified as autogenous pebble mill grinding, or better known as ore-pebble mill grinding. In the generic sense, pebble milling includes those grinding operations using a tum¬bling mill in which the grinding media consists of various types of pebbles, either ore or other pebbles, instead of metal balls. Conse¬quently, this subject is covered separately in Chapter 5, Pebble Mills. Operating data from many of the installations located throughout the world are included in this chapter. Our appreciation is extended to those companies who contributed this important information. History of Autogenous Grinding F. C. BOND Autogenous grinding, the grinding of ore by itself rather than by special metallic or nonmetallic grinding bodies distinct from the ore, has an old and honorable place in the art of mineral processing. It antedates the use of the rod mill and is only a few years younger than the development of the continuously fed rotating tumbling mill in which it is accomplished. Its history71, 72 is inextricably bound up with that of gold mining. Every important early development of autogenous grinding took place on ores of gold, except in one case of silver ore. In common with many other features of modern mineral processing, autogenous grinding would have been greatly retarded if the winning of gold had been so small a part of mining in the past as it is today. Gold unlocked the secrets of rock-on-rock grinding. In years past gold ores were crushed in stamp batteries and then flowed over copper plates covered with mercury which amalgamated the gold. The McArthur Forrest cyanide process for the dissolution of gold in a dilute alkaline cyanide solution appeared in 1890. With finer grinding it recovered more gold than could be won by amalgama¬tion alone. The first response was to stamp in cyanide solution and finer mesh screens guarding the stamp discharge. However, the fine screens greatly restricted the tonnage stamped, and they wore out rapidly. Rotating tumbling mills70, 73 were the obvious choice to grind the coarse product from stamps. Many of these were Gates tube mills; more than 1,000 of these were sold between 1907 and 1913. They were made in 6, 51h, and 5 ft diam, with lengths of 20 and 22 ft. The 5 x 22-ft size was the most popular. The term tube mill did not refer to the mill shape, but included all tumbling mills using grinding pebbles. The flint or chert rocks found along the coasts of Denmark and Normandy are probably the most durable and resistant to abrasive and tumbling wear of any on earth. They were much used in the early tube mills. The early linings were all silex or Danish flint blocks, cemented into place with portland cement. Local hard stones or cast iron blocks were also used later. The cast iron liners carried lifters and were not bolted to the shell, but were held in a tight circle against it by steel wedges hammered home between them. The first ribbed metal liners designed to hold grinding pebbles pounded into them by the mill action were developed at El Oro, Mexico, about 1905. These and the Forbes, Komata, and Tonopah types, as well as the Osborne type developed in South Africa within about five years, were very successful in reducing liner wear. They sometimes lasted two years or more, and equalled or exceeded the life of silex lining at a lower cost. Some of the types were patented. The pioneer name recorded in the history of autogenous grinding is that of Kenneth L. Graham. In 1907 at the Geldenhuis Deep Ltd. mine near Johannesburg, he ran a comparative test on two tube mills. One mill used pieces of the common gold ore, or banket, and the other used the customary imported Danish pebbles as grinding media. He published the first account of autogenous grinding.&apos;&apos; In a test lasting 81 days the ore pebbles showed a definite saving over the Danish pebbles. Graham&apos;s historic paper also describes the invention of B. Chew of the Crown Deep Mines of the first trammel to be attached to a grinding mill discharge. The first known account of autogenous grind¬ing printed outside of South Africa was the description of the Graham test in Mining and Scientific Press&apos;s The use of grate- vs. overflow¬discharge was also described at this time." The news of this successful test appears to have had immediate effect, for by the end of 1908 the number of tube mills on the Rand had increased from 72 to 120.76 Presumably, most of these mills were now using autogenous grinding. The ore was principally a hard conglomerate of quartz peb¬bles cemented by silica, and was eminently suitable for use as a grind¬ing media. It is unfortunate that in South Africa the new autogenous process continued to be called by its old name of pebble milling, since the name does not distinguish between grinding with ore and grinding with extraneous pebbles. For increased clarity the former is called rock pebble milling. The first historical stage in the development was what is now designated as secondary autogenous grinding, or rock pebble milling. It consists of grinding a feed all passing &apos;A in. or finer with ore pebbles about 2 to 4 in. in diameter. The next stage to develop was that now called intermediate autogenous grinding, where larger amounts of larger pebbles about 5 in. in size were used to grind ore which had been crushed to about rod mill feed size or somewhat finer. It was developed on the Rand and in other places where coarse stamp screens were used to increase mill tonnage. In many cases the early secondary and intermediate autogenous mills have now been replaced by conventional ball mills and rod mill-ball mill circuits, with the object of further increasing grinding capacity. The third stage to develop is designated as wet primary autogenous grinding, in which run-of-mine ore or a primary crusher product is all fed to the autogenous mill together. It developed many years later indepen¬dently in the United States and in South Africa. The fourth and most recent stage is that of dry primary autogenous grinding, which developed in the United States and Canada. All four stages originated in gold mining. The first use of commercial autogenous grinding outside of the Rand apparently took place five years later in 1912 at the Santa Gertrudis gold mine at Pachuca, 55 miles northeast of Mexico City. This was followed closely by an installation at Goldfields, Nevada, in 1914-1915. The first name associated with autogenous grinding

Jan 1, 1985

By Roy M. Fleming

During the decade of the 1970&apos;s, a new emphasis was placed on assuring a safe and healthful workplace for all American workers. Much of the basis for this national effort was federal legislation: the Occupational Safety and Health Act of 1970 and the Federal Mine Safety and Health Act of 1977 (amended from the 1969 Coal Mine Act). One of the agencies involved in this protection effort is the National Institute for Occupational Safety and Health (NIOSH) of the Centers for Disease Control (CDC) in the Department of Health and Human Services (DHHS). In fulfilling its mandates under the 1970 and 1977 Acts, NIOSH conducts research, experiments, and demonstrations to support and stimulate advancements in health and safety practices. Priorities for NIOSH research are established primarily through congressional mandates, requests from the Department of Labor, needs as defined by NIOSH researchers, and surveillance information. Emphasis is placed on research in the areas of toxicology, industrial hygiene, physical and chemical sciences, physiology, ergonomics, engineering, psychology (behavior and motivation), and epidemiology (industry-wide studies). The framework of the current Institute program to identify, evaluate, and control occupational hazards includes activities in surveillance, research, evaluation, and training. These activities are planned and evaluated through a system that coordinates the efforts of eight research and scientific divisions. Each division develops projects to address program areas that have been identified by NIOSH management as having highest priority. In surveillance programs, the objectives are to identify substances and agents found in a representative sample of workplaces and to collect and evaluate information on rates of disease and injury in occupational groups. Information is also collected on occupational safety and health programs implemented by industry. Estimates of worker exposures and the potential for adverse health effects are considered in setting priorities for further investigations. A related activity, which also serves to provide technical assistance to industry, is NIOSH&apos;s Health Hazard Evaluation program. On-site investigations of workplaces are made in response to worker, employer, or government agency requests. Both industrial hygiene and medical examinations are conducted, and the results contribute to identifying new problems and evaluating their significance which may have public health implications beyond the particular worksites that are investigated. Field and laboratory research projects are performed to meet several objectives: - Characterize the working environment by evaluating current and past exposure levels for workers who are included in epidemiological or medical investigations. - Develop epidemiological information to define the association between the substance or agent under investigation and the acute and chronic health effects on workers. - Determine through animal studies the parameters of an association between exposure and effect. - Investigate the etiology of disease. - Develop sampling and analytical instruments and techniques and demonstrate their application for measuring toxic materials in the workplace. - Formulate sampling strategies that will accurately and precisely indicate exposure levels. - Develop medical procedures to prevent disease and to detect the presence of disease and early indicators of disease. - Assess the technology for control of exposures, including engineering and administrative techniques, personal protective equipment, and work practices. Presently, the research program is focused on reproductive effects, neurotoxic effects, injury/trauma, lung disorders, cutaneous disorders, cardiovascular disorders, cancer, stress-related disorders, effects of physical agents, digestive disorders, and renal and other organic disorders. In studying these issues, priorities are determined by the seriousness of possible adverse health effects resulting from occupational exposures, the feasibility of studying existing records or obtaining new data, and the size of the population which is potentially affected. Where there is low level of suspicion concerning adverse health effects or where an occupational disease occurs in a variety of industrial environments, investigations are limited to gross analyses of health effects such as review of mortality patterns. In such studies, the industrial populations selected are those for which existing data resources can be utilized. Such data consists of records of occupational exposures or health status which have been maintained by the employer, the union, or Government agencies. Where a review of the available information suggests that serious health hazards exist and the existing data resources are inadequate for quantifying the relationship between the specific biological response and type and degree of exposure, prospective studies are initiated. Information derived from such research is essential for the development of sound criteria for control of industrial exposures to noxious agents. Other input to the criteria documentation process comes from searching and evaluating the literature. Criteria documents contain the recommendation of an environmental limit where information is available to support it, as well as the recommendation of work practice controls, medical evaluation, information for workers to recognize and avoid the hazard, and identification of specific research gaps. In some cases, during the criteria document preparation, gaps in knowledge are found which necessitate further research before an occupational standard can be recommended.

Jan 1, 1981

By Raymond E. Connell

From a macro business process perspective, if what we do in the Mining Industry is find material, dig it out of the ground, convert it to a product and sell it, we are in what might be considered a "simple business". If it is so simple, where does information technology fit? How does it affect our industry? Is it a strategic tool for our industry? What approach should we be employing to ensure we are utilizing information technology effectively? How is information technology integrated or tied together with other areas in the organization such as process control? What kind of people and skill sets are required to support the whole area of information technology? What effect does information technology and automation have on streamlining and rethinking the way we do business in the 90&apos;s. This paper covers how these areas have been addressed within the Noranda Group of Companies. It reviews how information technology has evolved, the approach, and what effect it has had on a diversified natural resources company in the mining and metals, forest products, and oil and gas industries.

Jan 1, 1993

By J. D. Decker, T. E. Norman

Introduction Grinding is the reduction of ore and similar raw materials to particle sizes below the practical limits of commercial crushing ma¬chines. This size is about 36 in. (1 cm), in most cases, although some finer crushing machines are in regular use. The feed size to grinding machines may range upward to S in. in rod mills, and 12 in. or more in autogenous mills. The finest particle sizes produced in mineral processing operations result from grinding. Ordinary grinding of brittle materials is the result of impacting, rolling, and abrasion of heavy bodies, moving freely under the influ¬ence of gravity. These falling and rolling grinding bodies, which are usually of metal, must be much heavier and larger than the ore parti¬cles they break. This weight relationship is usually in excess of 100: 1. The sustained fall of the grinding bodies is obtained by placing them, together with the rock particles they grind, in a rotating drum or cylinder with horizontal axis, called a tumbling mill. The mill is nearly half full of grinding bodies and ore particles, which may be fed into one end and exit from the other through hollow trunnions which usually serve as the mill bearings. The mill lining must be thick to absorb wear and rough to prevent excessive slippage of the charge. The breakage of brittle rock or ore is accomplished by compression. The compression may be a rapid impact, from the fall and roll of a grinding ball, or it may result from the relatively slow and constrained motion as in a jaw crusher. Breakage by shear is a secondary result of the compressive motion. Ordinary rock has an extremely heterogenous structure with innumerable zones of weakness in which cracks, fractures, and breakages can form. When a rock is subjected to com¬pression it deforms. If the compressive force exceeds a certain critical value an incipient crack appears in the most fragile zones of weakness. This crack tip may first form on the particle surface or in its interior. When the first crack tip forms the compressive stresses immediately surrounding it flow to it, and this concentration of forces extends the crack and splits the rock. Other adjacent cracks may form during this extremely rapid process. Because of the nature of brittle particles, the work done in breaking them consists essentially of the work input required to compress them to the point at which the first crack tip forms. Breakage requires no appreciable additional energy input be¬yond that required for the deformation, since the stress energy already imported to the rock flows to the crack tip and extends it to breakage. Types of Tumbling Mills The general term tumbling mill includes the rod mill, ball mill, pebble mill, autogenous mill, and tube mill. It is of cylindrical or cylindro-conical shape and rotates about its horizontal axis. Rotational speed, liner type, and size and shape of tumbling media are selected to provide the desired operating conditions for the specific grinding application. Openings are provided through the mill ends for feed and discharge of the material being ground. A common feature of tumbling mills is the use of tumbling media

Jan 1, 1985

By Jack J. K. Daemen

A wide variety of subsidence prediction methods exist. They can be classified into empirical methods and mechanistic models. The empirical methods include profile functions and influence functions (Brzuner, 1973a,b; Kratzsch, 1974; Berry, 1978; Hood et al., 1981), the two empirical approaches of most practical value, if only be- cause they are readily programmed on calculators or computers. The profile functions have the advantage that they allow for ready determination of the necessary empirical parameters from field observations. They have the disadvantage of being restricted to subsidence calculations at a very limited number of points or lines above very simple (rectangular) mine geometries. This reduces greatly their practical applicability for damage predictions, which usually require estimates of strains, slopes or curvatures at structures that have arbitrary position and orientation with respect to planned mine excavations. Influence functions can be used to calculate subsidence at any point near an excavation of any in- seam outline. The main difficulty associated with empirical influence functions is the lack of uniqueness in the relation between subsidence and its cause, the convergence distribution over a mined excavation and its immediate surroundings. A secondary practical difficulty is the need for fairly arbitrary adjustments near the excavation edges, usually in the form of compensation zones (e.g. Brsuner, 1973; Hood et al., 1981). Determination of the appropriate empirical constants in influence functions is facilitated greatly when a direct mathematical connection exists between influence and profile function (several examples are given by Brauner, 1973 and by Hood et al., 1981), so that field data can be used to determine the parameters through backfitting of the profile functions, which is considerably simpler and more direct than backfitting of influence functions.

Jan 1, 1982

By Stephen J. Crittenden

Deep gas and oil production has been substantially increased over prolonged periods through the use of sintered bauxite propping agents. Since its inception in 1976, over 170,000,000 pounds of high strength ceramic proppants have been employed. Recent field evaluations and economic analysis demonstrate the superiority of sintered bauxite proppant over quartz sand. This paper describes the development, application, field results, and product evolution of sintered bauxite.

Jan 1, 1983

By Clifford J. Lewis

The control of sulfur dioxide and fly ash in the emissions from coal-fired boilers is a significant segment of the national environ- mental protection program. Developing technologies to accomplish this objective presently emphasize aqueous scrubbing techniques. Should circumstances require aqueous scrubbing for fly ash control only, provision must nevertheless be made to counteract the presence of sulfur dioxide which can create an acidic and potentially corrosive environment. Major technologies for sulfur dioxide control by aqueous scrubbing include, l), recovery processes yielding sulfuric acid or elemental sulfur and 2), throw-away processes which produce a sludge consisting essentially of calcium sulfite or varying amounts of calcium sulfate.1/ Recovery processes are more sophisticated and best suited for locations where there are markets for sulfuric acid or sulfur, or where sludge disposal is an overriding consideration. Throw-away processes are generally less sophisticated but have a problem in that gas scrubbing systems may not operate for practical time periods without failures due to corrosion and to plugging by particulates and precipitates. To overcome this difficulty, some throw-away systems employ an aqueous solution of caustic in the gas scrubbing device to assure maximum water solubility of sulfur compounds, followed by the addition of lime to the scrubbing medium in a system external to the scrubber to produce the throw-away sludge and regenerate the caustic for recycle. Such systems are referred to as double alkali systems.2/

Jan 1, 1975