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By Frank F. Roxborough

The paper presents a brief account of the principal findings and an assessment of the practical value of a substantial international research effort into the mechanical excavation of rock that has been in progress over the past 30 years. This assessment together with an appreciation of the emerging trends in mechanical excavation suggests what are likely to be profitable lines of future inquiry.

Jan 1, 1985

By Martin H. Stanczyk

Under the Solid Waste Disposal Act, the Bureau of Mines initiated several accelerated in-house research programs to develop new and improved methods of proper and economic solid waste disposal. The program being conducted at the Bureau' College Park Metallurgy Research Center is concerned with eliminating the current waste of valuable materials in municipal refuse by developing low-cost methods for reclaiming and recycling the metal and mineral values contained in incinerator residues. Each year the United States must collect and dispose of in some manner or other, about 150 to 200 million tons of municipal solid wastes. The monetary output for this service ranks third among public services, exceeded only by the costs for schools and roads based on population growth projections and materials use patterns, the quantity of refuse generated by the early 1980's may approach 300 million tons annually. Currant estimates indicate that only 10 to 20 percent of the total municipal refuse generated is disposed of by incineration. If all refuse were properly incinerated the residues would contain more than 11 million tons of iron and nearly a million tons of mixed nonferrous metals including aluminum, copper, lend, zinc, and tin.

Jan 1, 1969

By A. E. Isaacson, T. H. Jeffers

The U.S. Bureau of Mines (USBM) is investigating arsenic removal from dilute waters using a biological precipitation/chemical adsorption system. The method includes (1) inoculating water with ferrous salts to increase hydrogen sulfide generation by indigenous sulfate-reducing bacteria, (2) utilizing the hydrogen sulfide to precipitate the bulk of the arsenic as arsenic sulfide, and (3) using beads containing ferric oxyhydroxide to remove the remaining arsenic. This approach was applied to a contaminated water containing 13 mg/L As. Arsenic extractions up to 99% were achieved. The use of sulfate-reducing bacteria is particularly warranted in this situation since most of the required nutrients are present in the water. Based on successful initial efforts, planning is underway to conduct a pilot-scale test at the site.

Jan 1, 1995

By M. A. S. Martins, J. C. Guillaneau

Steady-state simulation has been proving its usefulness and efficiency in process design and optimization for many years. Steady-state simulation is a very effective approach for plant design since it enables a great number of hypotheses to be considered regarding flowsheet, equipment etc., the processing equipment and material handling equipment to be sized, and the configuration of almost optimal industrial plant to be attained in a very short time. This paper will present the basic principles of mineral process simulation methodology and some real case applications of their capabilities in several complex ores in Brazil.

Jan 1, 1998

By J. C. Barker

Alaska, with about 74% of the US continental shelf, is largely unexplored for placers in its vast shallow marine waters. Nevertheless, there are numerous occurrences of marine minerals including gold, platinum, and cassiterite. Offshore dredging has recently begun in the Nome area. State and Federal agencies are preparing additional acreage for leasing. With 76,200 km (47,300 miles) or 54% of the US coastline, Alaska is a vast, largely unexplored frontier for shallow-water marine placers. Despite the general lack of mapping and only sporadic past prospecting, many prospects are known and a major mining operation for gold has recently begun offshore of Nome. Due largely to the demonstrated success of the Nome operation, the US Minerals Management Service is preparing to conduct a lease sale of additional acreage further offshore from Nome. And future sales are being considered elsewhere by both the Federal and state leasing agencies.

Jan 1, 1990

By M. S. Klima, M. Fofana

The use of a laboratory-scale magnetic fluid-based separator for coal separations was examined. A Frantz laboratory magnetic separator was modified by fabricating new pole pieces of the appropriate geometry to provide the proper magnetic field gradients. Two separation chambers, which were constructed of Plexiglas, were designed to fit between the pole pieces. A commercially available, water-based, ferromagnetic fluid was used as the separating medium. The separating density was changed by varying the current intensity of the electromagnet coil. Both batch and continuous separations were made using 0.59 x 0.50-mm and 0.18 x 0. 15-mm coal. The results are compared to those obtained using organic liquids.

Jan 1, 1998

By D. M. Bodily, V. J. Hucka

INTRODUCTION Interest in the recovery of methane from coalbeds has increased rapidly over recent years, because of its potential as an energy resource and to alleviate pollution and safety problems. The resource base of coalbed methane in the United States has been estimated at 11.2 Gm3, roughly equivalent to 20 years consumption (Mroz et al., 1983; Kuuskraa and Brandenburg, 1989). Methane contributes to the adverse environmental impacts of global warming, tropospheric ozone formation (smog), and potentially stratospheric ozone destruction. Association of methane with coal has always presented a safety problem in mines due to the potential for explosions. The rate of release of methane depends on the amount adsorbed by the coal, the adsorption isotherm for the coal, and the size of the coal particles. Mining operations can affect the particle size distribution and the production of fines and therefore the rate of release. The time the mined coal remains in the mine may also be important in determining total emissions. The methane content of some Utah coals was determined in this study. The methane content of the coals is compared with the chemical and physical properties of the coals and the properties of the seam and neighboring strata. Correlations are developed to better understand the formation and retention of methane by these coal seams. METHANE FORMATION IN COALBEDS Three mechanisms for methane formation may be considered: (1) nonbiogenic formation, (2) formation by anaerobic bacteria during plant material deposition and the early stages of diagenesis, and (3) formation from pyrolysis of coal material during coal maturation. Nonbiogenic formation by thermal processes involving carbon- and hydrogen-containing compounds has been proposed as a mechanism for methane formation in the earth. It is not likely to be of importance where other fossil fuel materials are present. Coal would not survive the temperatures required and hence the methane would need to migrate and be trapped by the coal seam. This mechanism is unlikely for coalbed methane. Formation of methane by anaerobic bacteria undoubtedly occurs during coalification, but the methane may not be trapped until the pore system of the coal is developed, and would likely be displaced by methane formed during further coalification. Methane formed by maturation of the coal material as it progresses from peat to coals of various rank is the most probable mechanism for the formation of coalbed methane. Most of the methane is adsorbed onto the walls of microvoids in coal. It has been estimated that the surface area of one kilogram of coal is between 20,000 m2 to 200,000 m2. Surface area measurements depend on the coal and also on the method of measurement. At 20 atmospheres, in some coals, the adsorbed methane is 10 times greater than methane as a free gas. At 100 atmospheres the adsorbed gas can be as densely packed as a liquid. The volume of methane gas held in coal depends on the volume of gas that exists as a free gas and the adsorbed gas capacity. The volume of free gas in the coal can be calculated from the kinetic theory of gases (methane can be assumed to be an ideal gas because errors would not be greater than 1 % for normal mining pressures). Langmuir (1916) derived an equation for the adsorption of gases on uniform surfaces and this is applied to the adsorption of methane on coal:

Jan 1, 1993

By Sheldon P. Wimpfen

Sand and gravel has been, and will continue to be, our principal construction material. Most of us are familiar with the patterns of past growth. Today we will examine the present status of this vital industry. We shall also attempt to look into the future to see where it is going and to evaluate the constraints that are being imposed. Natural aggregates are among the lowest in value of all bulk industrial minerals. From the processing point of view, sand and gravel production is relatively simple since the products are sized materials obtained from a deposit of satisfactory physical soundness. They can be used either loose or bound to provide bulk, strength, or protection. One of the main uses of coarse aggregate is in concrete as a filling material. As a general rule, the coarse aggregate constitutes about three-quarters of the volume of concrete. The other main use for aggregate is as a roadstone or roadbase to provide protective and stabilizing bulk beneath the road surface. Also it is used in a mixture with petroleum products as the wearing course on top. The sand and gravel industry is geographically widespread. In general, the output of operations is directly proportional to the amount of construction in any area. A wide variety of other aggregates compete with sand and gravel, including crushed stone, blast-furnace slag, clinker, and artificial and natural lightweight materials.

Jan 1, 1972

By Alfredo P. Vargas

Industrial flotation of sulfide ores is 80 years old. It has gone through many advances to date. However most flotation operations are still struggling to improve performance, which as a worldwide average is at the 90% level. What can be done to push the ceiling to 95% or better without performing finer primary grind, nor without duplicating flotation plant capacity? Such "unique task" can be performed by the low volume high capacity new flotation equipment known as the JAMESON CELL, when used as, "post-scavenger" of final plant tails. Improved efficiencies are obtained mainly from two cases: -Particles which never contacted a bubble. -Particles sheared-off by cell turbulence due to reduced number of hydrophobic sites. The application reverses conventional trend of using large volume mechanical cells by trade-in with smaller efficient equipment: resulting in reduced capital expenditures and operating costs. Outstanding "pre-rougher" applications are also presented.

Jan 1, 1993

By Graham Taylor, Mandy Agnew

Hardpans developing in tailings storage facilities (TSF) in Australia have been investigated in relation to Acid Rock Drainage (ARD) generation. This research had three main aims. Firstly it was to obtain an understanding of the physical and chemical characteristics of tailings residues which support the in-situ formation of cemented layers and hardpans. Secondly it was to examine how effective hardpans are at reducing ARD generation, and thirdly it was to investigate the promotion of hardpan formation to inhibit ARD and pollutant generation. This paper presents the data collected during investigations into the effectiveness of hardpans to reduce ARD generation. Three basic types of hardpans have been identified and examined: laterally extensive surface hardpans, laterally extensive cemented layers; and laterally discontinuous hardpans developing in locations of seepage. Their mineralogy, morphology, lateral extent, depth and rate of formation are dictated by sulfide and gangue mineralogy and content, milling and depositional techniques of the tailings and the climate. As the sulfides oxidise, acid and heavy metals are generated, while gangue mineral degradation is enhanced, adding to elemental loads. These liberated ions are then available for precipitation of secondary mineral cements through concentration during evaporation. In TSFs where hardpan development is restricted by mineralogy, grain size or climate, hardpan formation can be enhanced in seepage zones (eg. seepage from waste rock dumps) where tailings are exposed to seepage waters laden with heavy metals and sulfate. The effectiveness of hardpans in the inhibition of ARD generation is dependent on reducing oxygen diffusion and water infiltration into the underlying tailings. A reduction in water infiltration will diminish the transport of contaminants developed during sulfide oxidation and subsequent reactions. Water and gas movement through the hardpans at the CSA (Cu, Zn, Pb) and Elura (Pb, Zn, Ag) mines has been investigated. Permeability tests indicate the hardpans have reduced the infiltration rates by 10 to 100 times that of the fresh tailings. Oxygen diffusion rates were calculated and were shown to be up to 1000 times lower in hardpans than in fresh tailings. Such decreases are explained by persistent elevated 'degrees of saturation' within the hardpans. These conditions were verified using a conceptual model of sulfide oxidation reactions, which allowed comparisons of diffusion coefficients with modelled and observed depths of oxidation within the tailings impoundments.

Jan 1, 2000

By D. Gärtner, A. Oster

"""Operational excellence"" provides a sound foundation for RWE Power AG's three strategic pillars (innovation, expansion and organic growth). The maintenance and development of operational excellence in lignite mining operations at RWE Power is supported by the Continuous Improvement Process (CIP) ""immer:besser"" (getting better). Obtaining cost reductions with the aid of the CIP as a kind of value-adding self-renewal process to ensure competitive lignite mining operations and lignite-based electricity generation forms the basis for further increases in profitability and growth. Since the beginning of the 1990s, RWE Power has carried out a multitude of re-engineering projects focusing on the efficient shaping of processes with the assistance of external consultants to enable the Company to cope with the considerable need for change by swiftly implementing major efficiency levers. These also include the required adaptation and development of the organization. Since 2004, the Continuous Opencast Mine Improvement Process (""KVT"") has enabled the mines to tap significant cost reduction potential by virtue of their own strength. But there is another issue that has come into focus: the development of performance enhancement options. In 2006, the ""KVT"" process, piloted in the opencast mines, was included in the RWE Power-wide immer:besser (i:b) programme (Figure 1)."

Jan 1, 2011

By Kenneth A. Gutschick, Harry L. Francis

A large number of minerals and chemicals (Table 1), some mineral-derived, are used in the treatment of both potable water and domestic sewage waste water and solids (Anon., 1990). In water treatment there are ten principal process uses as shown in Table 2 (Anon., 1990), which also lists the major chemicals in each process. Since lime (calcium oxide, calcium hydroxide, and dolomitic lime) is the largest chemical (by tonnage) used in water treatment, this chapter will deal primarily with this product. Note that it is included in five of the process uses shown in Table 2, and that indirectly it is also used in at least one other category (taste and odor control, where lime is used with potassium permanganate to provide optimum pH condition). POTABLE WATER TREATMENT Water Softening The biggest use for lime in water treatment involves water softening, where it serves to reduce carbonate hardness caused by dissolved bicarbonate and carbonate compounds. Currently there are more than 1000 domestic water softening plants (Table 3) located in most sections of the country, but particularly in Ohio, other midwestern states, Florida, and Texas, where limestone bedrock abounds (Anon., 1990). Among the other uses for lime in water treatment are coagulation, disinfection, and removal of heavy metals due to high pH softening, removal of certain radioactive and organic compounds and fluorides, neutralization of acidic water, removal of silica, particularly with dolomitic lime, and removal of color. Most of the above advantages accompany water softening, although at some plants lime is used specifically for one purpose, such as silica removal with dolomitic lime, minimizing pipeline corrosion by addition of lime to correct an aggressive water, and others. Hardness in water comprises two types - carbonate hardness, caused by dissolved calcium and magnesium carbonates and bi- carbonates, and non-carbonate hardness caused by dissolved non- carbonate salts, particularly calcium sulfate, calcium chloride, magnesium sulfate, and magnesium chloride. Total hardness is the sum of the carbonate hardness and non-carbonate hardness. Waters are classified as soft (0 to 75 mg/L as CaCO,), moderate (75 to 150 mg/L), hard (150 to 300 mg/L), and very hard (above 300 mg/L). Most water plants strive to reduce total hardness to about 100 mg/L, although in recent years the tendency in some cities has been to allow a little higher value in order to reduce both chemical costs and the amount of water softening sludges produced. There are four basic types of softening plants: lime softening, primarily to reduce carbonate hardness; lime-soda softening, for reduction of both types of hardness (in some plants caustic soda is used in place of soda ash, but it is more costly); split lime-zeolite, where a base exchange mineral is employed in place of soda ash (this system also requires salt [sodium chloride] to regenerate the zeolite mineral); and finally zeolite softening, which is generally used in small systems for private houses and small municipalities. Principal disadvantages of the latter system are its relatively high cost and the salt requirement, which introduces considerable quantities of soluble salts into the waste water discharge system.

Jan 1, 1994

By J. P. Ramsey

This is a description of the efforts of a research project intended to demonstrate methods of alleviating pollution from coal mine refuse piles and slurry lagoons. These are mainly derelict barren sites. Some are burning and some are vulnerable to wind erosion which causes air pollution. Some occupy valuable land near metropolitan areas. They are an integral part of the landscape of the Appalachian and Midwestern Coal Fields. They are important in the light of growing civic awareness of the great general problem of waste disposal and environmental improvement. In the V-shaped valleys of the Pocahontas Region, they continue to be piled higher and higher. In flatter topography, they tend to form broad, flat ridges. Some contain more metal forms than others and some have a minimum of metal, but weather to a fine talc, which chokes streams with a fine particle suspension. Most are burning or have burned, but burning or weathering, most all are sources of pollution to the atmosphere and to adjacent waterways. This demonstration project is being carried out at an abandoned mine near the town of Du Quoin in southern Illinois. It is jointly sponsored by the Truax-Traer Division of Consolidation Coal Company and by the Federal Water Pollution Control Administration of the Department of the Interior. The site area is a refuse pile and slurry lagoon, each of fifty acres. It is hoped that basic data from this study will be generally applicable to other sites and will provide a basis for rational and efficient engineering design of future reclamation projects. Most refuse piles have extremely long term capabilities to produce highly potent acidogenic oxidation products typifying the more serious aspects of acid mine drainage contamination. Numerous sites remain where the abandoned mine no longer discharges acid waters, but its associated refuse pile continues to generate significant quantities of acid and other oxidation products even after many years.

Jan 1, 1969

Bismuth, "the green metal," has become an important substitute for lead. The uranium industry was never really dead, anti-nuclear activists just wanted the world to think it was. And diamonds are fast becoming a miner's best friend. These commodities and others were discussed in May 1997 at the 47th Annual Minerals Processing Division meeting, held at the Broadmoor resort in Colorado Springs, CO. The meeting was put on by the SME Colorado subsection and was attended by about 115 people. In addition to the above three commodities, attendees learned more about the state of the copper industry, as well as lead and zinc and gold and silver. The program also included discussions of molybdenum, platinum and project financing. The following is a summary of some of the presentations.

Jan 1, 1997

By Eric Monrad

Discrete event simulation modeling provides a tool to quantify the throughput capacity of stockyards. Interactions between the main equipment types (trains, dumpers, conveyors, stackers, reclaimers, shiploaders) can be captured, including route blockages, breakdowns, and planned maintenance. Simulation has been successfully used at world-class stockyard facilities to determine current capacity and to identify gains resulting from improvement projects. Recent projects have focused on iron-ore, coal, and soya facilities, but the technology is suitable to be used on any bulk material type.

Jan 1, 2008

By R. H. Moore, B. D. Breitenstein

INTRODUCTION The United States Uranium Registry (USUR) tissue program was funded in 1978 by the United States Department of Energy (DOE) through its Human Health and Assessments Division, and registrant enrollment began in 1980. It is operated by Hanford Environmental Health Foundation (HERF), Richland, Washington, with support provided by Pacific Northwest Laboratory (PNL).** The USUR tissue program is the first systematic effort to contact and gain assistance of workers occupationally exposed to uranium and to seek and study uranium deposition in human tissue. This paper describes the program objectives, populations selected for study, procedures for enrolling workers in the program, types of tissue to be studied, and analytical procedures to be used. PROGRAM OBJECTIVES The objectives of the USUR tissue program are to: 1) Determine the distribution and concentration of uranium, if any, in the tissues of occupationally exposed workers. 2) Compare bioassay measurements of exposed individuals with the results of analyses of tissues obtained at autopsy. 3) Seek evidence of histopathologic changes related to any uranium deposition that may be present. 4) Conduct analyses of whole bodies, when available, to obtain more precise data on the uranium burdens, if any, in the body and organs, and especially the distribution in parts of the body, such as the skeleton, that are not usually accessible for sampling. 5) Develop data that will assist in evaluating a) the accuracy of current in-vivo measurement techniques, b) the propriety of existing regulations, and c) the adequacy of current protection programs. SELECTION OF POPULATIONS FOR STUDY Selection of the populations for the USUR tissue program was based on studies of the United States Uranium Registry described elsewhere (0c81). Potential populations for study were quite varied because of occupational exposure to different chemical forms of uranium, different levels and eras of exposure, varying ability to identify populations exposed in the past, and the general interest and cooperativeness of the populations. Nevertheless, certain identifiable populations emerged that were both willing to participate in the study and likely to provide useful information. Among the targeted populations are individuals who were exposed to uranium prior to the existence of modern exposure standards. These individuals are presently being enrolled by the USUR. The reliability of concentration and distribution data and the demonstration of effects are more likely in such individuals than in those who have received less exposure. However, the targeted groups also include individuals who Have been exposed to permissible levels of uranium, and reference employees in uranium plants who have not worked with uranium. The lesser exposures are of immediate interest because of the rarity of heavy exposures under current standards. The sampling of potentially exposed individuals with negative in-vivo measurement results may serve to check the adequacy of in-vivo measurements in the detection of deposition. [ENROLLMENT PROCEDURE] The enrollment of participants follows three patterns. 1) Presently employed workers are enrolled by the cooperative efforts of USUR staff with the medical, industrial relations, and/or health physics personnel of the uranium facility. Volunteers may be enrolled by medical personnel at the time of their physical examination or by health physics personnel at the time of a bioassay or lung counting procedure. Follow-up after initial contacts with currently employed uranium workers is carried out by on-site personnel, but subsequent follow-up is the responsibility of the Registry. 2) Retired workers are contacted by mail, with a covering letter from their former employer supporting the principles of the study but leaving participation in the program on an entirely voluntary basis. 3) An alternate method of enrollment is to obtain a USUR autopsy consent after death from the next of kin. As part of enrollment in the program, permission is requested for access to the individual's medical and exposure data, and a short occupational history is filled out. The autopsy permission agreement signed by the individual is for an initial period of 5 years; the USUR ordinarily seeks renewal of the agreement upon its expiration. While this agreement provides

Jan 1, 1981

By R. R. Klimpel

In three recent publications, Klimpel et al (1988) and Klimpel and Hansen (1988, 89), the theory and invention process behind the identification of two new classes of sulfide mineral collectors were summarized. These two new families can be represented by the 111 generalized formulate: R1-S-R1 -NRI III (denoted as the F-series chelation family) and R-S-R or R -CHSCH-R (denoted as the S-series redox family). The influence of systematic changes in the various R groupings on laboratory batch flotation cell tests has been covered in the above references and will not be repeated in this paper. In particular, the recent article by Klimpel and Hansen (1989) should be studied as a research introduction to this paper.

Jan 1, 1989

By M. Carvalho, R. Bicallho, M. Queiroz, R. Gomide, V. Silva, R. Toubes

Since it is becoming increasingly important, from an environmental viewpoint, to minimize blast vibrations induced in urban dwellings and improve rock fragmentation in order to reduce costs with loading, transportation crushing and grinding, a cooperative research project was established between Companhia Vale do Rio Doce - CVRD and the Blasting Research Group in the Department of Mining Engineering at Escola de Minas - UFOP to investigate which elements interfere on ground vibration, air blast, flyrock and rock fragmentation related to rock blasting activities at Conceição Mine, located in Itabira city, state of Minas Gerais, Brazil. This research also involved development of a new explosives formulation in order to minimize the total blasting cost. This paper presents the general scheme of the research running from May 1995 to May 1997 and a summary of the results obtained in the field tests that were carried out in this mine.

Jan 1, 1998

By J. J. Fallon

Las Vegas is a place of many distractions. It is difficult for one to apply himself to sophisticated technical matters in the midst of gambling, liquor, scantily clad young ladies and the top entertainment available in the United States. But, I know that the men and women of SME are made of stronger stuff and will not be tempted by these things.

Jan 1, 1989

By D. Borrowman

Attrition of activated carbon in either the carbon-in-pulp (CIP) or carbon-in-leach (CIL) method of gold extraction can lead to, at the least, loss of expensive carbon that has to be made up, and at the worst, loss of both the carbon and any gold that was attached to it. Carbon attrition therefore represents a significant factor in both the efficiency and cost of the extraction process, and efforts to reduce attrition through process and equipment selection pay dividends. In evaluating carbon attrition potential, one would note that an individual carbon particle is in jeopardy virtually any time it is in motion. Since the motivators of this motion are primary centrifugal pumps, the purpose of this paper is to review the current styles of these pumps now in use and to examine their performance in minimizing carbon attrition.

Jan 1, 1992