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By B. J. Arnold, F. F. Aplan, R. R. Klimpel, E. C. Jr. Dowling

Residence-time distribution techniques are useful tools in the analysis, characterization and modeling of the performance of processing equipment and circuits. This paper presents the results of both conventional and more-sophisticated residence-time distribution techniques for industrial copper-flotation-circuit data. While conventional techniques provide a description that is sufficient for macroengineering design requirements, the more sophisticated tracer-technique methods give more realistic descriptions of process flows and system effectiveness. It is demonstrated that these approaches can provide highly useful information about different equipment, as well as its configuration and performance.

Jan 1, 2000

By Jan A. Nemcik

Steel mesh has been used successfully for many years to control friable roof conditions and prevent loose roof and rib material from caving into the roadway. Despite its extensive use, the installation of steel mesh is difficult to automate and many other products have been evaluated as an alternative for skin control. Ideally, the properties of these new products should be similar or better than those of the steel mesh. In particular, development of a strong and resistant shell that minimizes movement along the fractured rock and coal surfaces between the bolt anchors is recommended. A strong surface adhesion and the strength of a reinforced polymer skin can provide the necessary toughening mechanism required to enhance roadway surface support by forming a reinforced polymer/rock surface layer. Most of the Thin Spray-on Liners (TSL) evaluated in the mines are weak with slow curing times, and the plastic mesh currently used to support the coal ribs is relatively weak. Therefore, neither material can seriously compete with steel mesh. Currently, a new polymer product that cures in seconds and forms an instantaneous strata binder that surpasses the properties of steel mesh is under development at the University of Wollongong.

Jan 1, 2009

By Richard H. T. Garnett

In 1900, placer gold was discovered on the beach of Nome, AK on the southern coastline of Alaska's Seward Peninsula (Garnett, 1991). The site is about 800 km (500 miles) from Anchorage. Nome is connected to Anchorage only by air (daily) and by sea (summer). Total onshore placer gold production from Nome's immediate vicinity was more than 155.5 t (5 million oz). Alaska Gold Co, has continued to produce gold onshore with, until recently, two bucketladder dredges, each of 255-L (9-cu ft) bucket capacity. Small-scale marine dredging for gold has been at- tempted several times this century (Garnett, 1991). Western Gold Exploration and Mining Co. Ltd. Partnership (WestGold) is the only company to have been successful in achieving a significant offshore production. The Nome bucketladder-dredging operation from 1986 to 1990 constituted a unique marine-mining experience in the United States. \Inspiration Gold Inc., WestGold's predecessor, acquired six offshore leases in 1985. The total lease area of 87 km2 (21,551 acres) extended from the coastline to the 4.8-km (3-mile) offshore limit (Fig. 1). Those leases al- ready had been partially explored. Drilling was conducted off the shorefast winter sea ice. Therefore, it was rarely more than 1.6 km (1 mile) from the shore or in water deeper than about 9 m (30 ft). In 1985, estimated reserves comprised of a 5-m (17-ft) vertical thickness of sediments below 6.3 m (20 ft) of water. This meant a mean digging depth below the mean sea level (msl) of 11.3 m (37 ft). It was thought that the offshore Nome deposit possessed a feature that is common with many terrestrial gold placers - the secret of profitable exploitation of the marine deposit lay in maximizing the dredge throughput to minimize the unit costs. The inability of the project to withstand the prohibitively high cost of a new dredge was recognized. So Inspiration Gold purchased a used unit. This was the world's largest ocean- going bucketladder dredge (Fig. 2). Binzn was an 850-L (30 cu ft) bucket capacity dredge that was lying idle in Singapore. Originally constructed in the Jurong shipyard of Singapore in 1979, Bima was designed by Mining and Transport Engineering, a subsidiary of IHC Holland. Billiton Marine used the dredge for tin production at Pulau Tujuh in Indonesia (Dieperink, 1978) before it was laid up in mid-1985. Bima underwent a nine-week refit before departing Singapore on June 4,1986, with 800-t (880-st ) of deck cargo. It was dry-towed for 32 days to Alaska. A slower, less expensive, wet-tow at the authorized 5.5 kmthr (3 knots/hour) would have delayed the dredge's arrival in Alaska untl almost the onset of winter. The 13,000-km (8,100-mile) voyage was made on the deck of Smit Lloyd's "Giant-4" submersible barge towed by its 7.8- MW (10,500-hp) tugboat. The first season's dredging revealed several major shortcomings in Bima. Further repairs and modifications were undertaken at Tacoma, WA. The dredge returned to Nome for the June start of the 1987 summer dredging season. The refitted Bima worked offshore at Nome from 1987 to 1990. It produced 3.67 t (118,078 oz) of gold at an average recovered grade of 824 mg/m3 (0.0204 oz/cu yd). In 1991, the dredge was dismantled and sold.

Jan 1, 1997

By Bilgehan Kekec, Sertac Dündar, Niyazi Bilim

"Knowledge of the abrasion resistance of aggregates is important when using them for asphalt and concrete mixes and highway construction materials. In this study, the usability of natural building stone waste as aggregates for different engineering applications was investigated. To this end, test samples were obtained from a number of natural stone quarries and stone cutting factories. The abrasion tests were carried out on the test samples and results were compared between samples. The abrasion strength values were determined with both the Micro-Deval (MDe) and the Los Angeles (LA) abrasion test methods. A correlation coefficient was also determined between the LA and MDe tests results using an appropriate statistical model.Introduction The rapid consumption of natural resources has led researchers to work on the efficient utilization of such resources. To this end one can convert waste into useful raw materials, or determine alternative uses of the industrial waste materials. This has become increasingly important as storing or dumping waste may result in environmental problems. In addition, the use of industrial waste in a different application of the construction industry prevents rapid consumption of limited natural resources and can mitigate environmental problems related to raw material production, Industrial waste such as blast furnace slag, fly ash, building demolition material, marble waste and dismantled asphalt have been used as highway and concrete materials (Ahmed 1993, Ramaswamy and Aziz 1992, Schroeder 1994, Ceylan and Manca 2013, Holtz and Eighmy 2000, Hebhoub et al 2011). It is very important to analyze whether these aggregates are of the required quality in terms of their application and their economic life. This analysis can be carried out using various tests such as the Micro-Deval and the Los Angeles abrasion tests, sieve analysis, durability chemical resistance, peeling and adhesion, and freezing-thawing tests (Erdem et al 1996). Specifications for aggregates also include terms that define the grain shape, cleanliness and surface textures."

Jan 1, 2017

By C. K. C. K. Gupta

The rare earths in elemental form are required for a variety of scientific and technological purposes. They are not easily obtained in this form, due to the great chemical stability of the rare-earth compounds and the strong tendency of elemental metals to react with everything they come in to contact with, especially at high temperatures. Beginning in the 1950s, when sufficient quantities of separated rare earths became available, as the result of intense research and development, three processing routes were developed to accomplish the preparation of all 16 naturally occurring rare-earth elements. They are chemical reduction of the halide intermediates, the oxides and electrochemical reduction of chlorides and oxide-fluoride mixtures. Not all the processes are effective with all the rare earths. In spite of the celebrated similarity of trivalent rare earths, the physical properties of individual rare-earth elements are sufficiently different that a variety of techniques are required for their preparation. The development of reduction processes for the rare-earth metals are covered in this paper, with focus on the oxide reduction routes. The strong reliance of effective reduction processes on the fundamental science of reduction reactions is highlighted.

By A. S. Kane

According to the 1966 Bureau of Mines Mineral Year Book only three states reported production of lignite in that year. These state: were North Dakota, Montana, and South Dakota; although it is known that there is production of lignite in Texas, California and, perhaps, Arkansas. In the year 1966 North Dakota produced 3,543,000 tons of lignite, Montana produced 328,000 tons of lignite, and South Dakota produced 10,000 tons of lignite. In view of the fact that North Dakota produces approximately 95 per cent of all the lignite reported in the United States, in discussing lignite mining, my remarks will be confined to lignite mining as conducted in North Dakota and will be confined to the production of lignite by stripping methods, as this is the predominate method used today. The first lignite mining in Worth Dakota, undoubtedly, was done by people settling in the western part of the state where wood was scarce and where lignite is exposed in the banks of creeks and ravines. The first production records were kept in 1884 and indicate that 35,000 tons of lignite were mined that year. The growth of the lignite industry has been very slow during the intervening period, but in 1966 production started to increase, and it is now indicated that production in the next few years may approach 6,000,000 tons per year. Ninety-seven per cent of the lignite produced in the lignite area of the Midwest is utilized in the generation of electric power, and it is anticipated that this use will predominate during the next two decades.

Jan 1, 1968

By M. Henneman, M. Kosma, M. Eyll-Vetter

"For a long time, the recultivation of depleted opencast mines and operating systems was aimed at restoring the original state. The focus, as desired by policy-makers and the local population alike, was on restoring high-quality agricultural land and on creating reforested areas of value that suit their location. Until the turn of the millennium, recultivation measures were only rarely the subject matter of public planning processes beyond these general objectives. They were never regarded as nucleus and origin of sustainable structural developments. The rehabilitation of inactive lignite opencast mines in central and eastern Germany brought about a change in mind-set that understood recultivation to be a unique opportunity to completely redesign a landscape and gear it towards the future in the Rhenish mining area as well. The ""Inden residual lake"" and ""terra nova"" projects, planned in the last 10 years in cooperation with policy-makers and authorities, are two undertakings that provide sustainable structural impetus for the future today."

Jan 1, 2011

The deformation, failure, and filling characteristics of a caving roof in the initial and normal mining stages of a pitching oblique longwall mining area are analyzed using large-scale threedimensional physical-similitude experiments and numerical calculations to study the characteristics of roof fracture and migration in a steeply dipping seam. The results show that the roof fracture development has evident sequential and spatial characteristics. Among them, immediate roof breaking in different parts of the mining area shows difference in time and space. The failure sequence of the immediate roof in different areas changes with the mining; unique regional stability evolution characteristics are observed in the suspended immediate roof simultaneously, resulting in its significant regional stability on the goaf filling.

Jan 7, 2020

By Keith G. Papke

Industrial-mineral mining started early in the history of the State when salt was extensively mined for use in processing gold and silver ores, and borates were produced to meet most of the world's needs. After this start, industrial-mineral production grew slowly until World War II, mostly because of the remoteness of the State and the small population. Nevada now has a large and varied industrial-mineral industry. In 1983, 14 principal commodities were produced from 48 deposits; the total value of these materials was 168 million dollars. Nevada ranks first in domestic production of barite and magnesite; second in diatomite, gem stones, and lithium; third in fluorspar; and sixth in gypsum. Other materials produced are carbonate rocks, cement, clays, decorative and crushed stone, light- weight aggregate, perlite, pyritic soil additive, salt, sand and gravel, and silica. From 1978 through 1982 barite was the most important commodity; in 1983 diatomite surpassed barite in value of production. Most of the Nevada production consists of high-value commodities that are consumed out of the State. Approximately 430 significant deposits with 20 principal commodities are present in Nevada. This abundance can be attributed to the numerous and diverse geologic processes that have been operative. Seven major modes of origin have been identified: hydrothermal activity, sedimentation, combined hydrothermal activity-sedimentation, evaporative precipitation, brine formation, extrusion of igneous rocks, and alteration by ground water. The hydrothermal type accounted for 39 percent of the deposits, the combined hydrothermal-sedimentary type for 28 percent, and the sedimentary type for 13 percent. Nevada diatomite production is about 200,000 short tons/year valued at 30 million dollars. In 1984 three companies operated in Nevada producing diatomite from six open pits and processing it at four plants - one plant producing filter-grade materials and the others adsorbents and fillers. The diatomite occurs in about 60 areas, almost all in the western one-third of the State. The diatomites were deposited in long-lasting, fresh-water lakes in topographically closed valleys formed by basin-and-range faulting. About 85 percent of the barite mined in the United States is produced in Nevada. In 1981 the high point of production,-2.5 million short tons of bedded barite was produced from about 30 open-pit mines. About 120 significant bedded-barite deposits are known in Nevada; 38 of these have had past production of more than 25,000 short tons. The deposits are associated with marine siliceous rocks of Cambrian through Devonian age and occur in a zone about 300 miles long and 60 miles wide. Abundant evidence supports the theory that the bedded barite is of exhalative sedimentary origin.

Jan 1, 1987

By P. C. Kapur

The hierarchical relationship between three broad kinds of grinding models for a spatially homogeneous, linear, time-invariant batch grinding system are first established. Limiting and asymptotic arguments for arriving at approximate but simpler models are employed in all three cases. These parsimonious models -provide alternate and, in some respects, more incisive and convenient tools for the analyses of grinding processes and simulation of comminution circuits. In the discrete-size, discrete- time class of models, a reduced mill matrix is derived, which is seemingly adequate for those grinding circuits whose identification otherwise is difficult because of limitations on the quantity of data and its quality. In discrete-size, continuous-time types of models, parameter lumping has been employed for obtaining a G-H solution which is quite accurate and exceptionally useful for graphical display of data, model verification, and parameter estimation and simulation. In continuous-size, continuous-time models, a similarity transformation is used for solving the integrodifferential equation of grinding. This solution provides a unified framework for a number of apparently diverse empirical grinding phenomena such as self-preserving behavior of ground particle size distributions and energy laws.

Jan 1, 1987

By W. J. Nelson

Detailed underground geologic map- ping at a scale of 1:1200 has been carried out at the Crown II Mine of Freeman United Coal Mining Company, which operates in the Herrin (No. 6) Coal Member. The roof sequence, upward from the coal, includes (1) soft, medium- to dark-gray shale; (2) hard, black, fissile shale; (3) argillaceous nodular-bedded limestone, and (4) fine-grained, shaly, water-bearing sandstone. The first unit is highly lenticular, and any or all may be missing at a given locality. The sand- stone has a sheet facies and a channel facies. The Herrin Coal is eroded in channels near the Crown II Mine. Structural features mapped at Crown II include normal and strike-slip faults of small displacement, "slips" and clay dikes, and limestone "bosses." Less stable roof and wet con- ditions are encountered where the limestone is thin or missing or where it is broken by natural fractures or by artificial openings that inter- sect the water-bearing strata above the limestone. Geologic mapping of the underground workings has allowed us to predict faults, fracture zones, and channels ahead of the face for this mine. Some lithologic and structural patterns apparently are random and cannot now be projected. Conventional exploratory drilling is entirely inadequate to map faults or lithology of the roof, but it does indicate the range of lithologic variability, which can be used to project needs for roof sup- ports. Drilling also is useful In locating channels and in mapping regional variation in thickness and facies of the sandstone.

Jan 1, 1980

By P. Schilizzi

The increased impact of mining subsidence in the U.S. coalfields and the recent regulatory constraints legislated by government and state agencies have provoked an intense research effort on this topic by government agencies, coal companies and academic institutions. Subsidence and horizontal strain predictions are a basic requirement if subsidence and its associated effects are to be controlled and contained within acceptable environmental levels. As a result, several such prediction techniques have been proposed or are currently under development to assist coal operators in minimizing the detrimental effects of these surface deformations. VPI&SU has been actively involved in this research effort in the past few years, with particular emphasis on the Appalachian coalfield. During the initial stages of this research a large number of subsidence case studies were collected from the literature, the coal industry and government agencies. In total, data from 32 longwall panels and 60 room and pillar panels were collected. This data bank was used to determine relationships between the basic mining and subsidence parameters, in order to allow the evaluation of the various prediction methods for the Appalachian coal region. Based on this data two subsidence prediction techniques, one based on profile functions and the other on influence functions have been developed. Profile function methods provide a tool for a fast calculation of subsidence on a line across a mine panel. Influence function methods, on the other hand, allow for a more detailed calculation of ground movements, in any mode and at any depth, on a grid or at any specific point. The limitations of the data of the collected case studies, i.e. accuracy of surveys, frequency of monitoring, lack of horizontal movement measurements, etc, led VPI&SU to the initiation of a detailed subsidence and strain monitoring program above a number of active mines, located in three major coal producing counties of Virginia. The aim of this program was to enhance the data base with accurate and complete measurements of surface movements and to allow, therefore, the refinement of the prediction techniques. This paper presents this monitoring program, discusses in detail the results obtained from three specific case studies and provides recommendations for the implementation of the field data in the general prediction methods.

Jan 1, 1986

Recent expansion programs have made the Yunkang underground coal mine the number one producer in Shenxi Province. The mine is the newest in the Datong Coal Administration, currently rated at around 3 Mt/a of coal. Located in the Wa Chushi mountain range about 23 km north of the city of Datong, the mine has undergone a series of expansion phases since startup in 1973. Initial design capacity was 1.5 Mt/a and ultimately, production will be brought to an estimated 7.0 Mt/a by 1985, according to mine superintendent Li Jia-zhi. How Coal Occurs The coal, Jurassic in age, occurs in three economically identifiable seams designated No. 2, 3, and 7. Seams are 100-250 m below the surface. Reserves from this economic zone were not quantified, but Superintendent Li indicated that there was enough mapped out to sustain the expanded production rate for over 20 years. Below the Jurassic coal is another possible economic zone, a Permocarboniferous coal lying 400-600 m below the surface. Little development drilling has been conducted to ascertain its potential. The Jurassic beds are relatively flat and coal quality is reportedly one of the best in China. Heat content of the coal runs around 33.5 MJ/kg and the ash content is less than 10%. In some areas, it is less than 7%. Coal preparation is simple and involves a washing and screening separation into four principal size fractions. Washed coal is stored in one of six storage silos, each with 4000-t capacity. Mining the No. 2 Seam Since startup, primary production has been derived from the No. 2 seam. The coal is relatively hard and is topped by a hard cement-like conglomerate. These factors, coupled with an average thickness between 4 to 6 m, precluded the use of conventional longwall techniques, according to mine engineers. The solution was development of a room-and-pillar tech-

Jan 3, 1980

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 D. Elsworth, M. Bai

The influence of mining on the hydro-geo-mechanical environment can be greatly modified by alternating mining geometries. The limiting magnitudes of surface subsidence and groundwater flow over the mining area, as a result of mine geometric changes, can be reasonably predicted through the coupled finite-element model introduced in this paper. The model has been verified using real and conceptual case studies which reveal that changes in strata conductivities are strongly related to the strata deformation induced by mining. The greatest modification of hydraulic conductivities occurs within the caving or severely fractured zones. The study indicates that narrowing the panel face width will substantially reduce both the intensity and extent of mining damage to the overlying strata, limit surface subsidence and constrain the change in hydraulic conductivity to a reduced scale and smaller extent, particularly as mining depth increases.

Jan 1, 1995

By K. Hanumantha Rao, K. S. E. Forssberg, H. R. Manouchehri

The fundamentals of electrical separation, the electrical properties of minerals, the principal methods used for charging minerals and their mechanisms, the effective factors controlling the acquisition of charges by minerals, the general configuration of commercial electric separators and the forces operating during electrical separation of minerals are reviewed and presented.

Jan 1, 2000

By Dennis W. Leonard

Let us begin our discussion by looking at historical and current levels of sales of both natural and synthetic zeolites on a world-wide basis. Due to the understandable reluctance of some companies to disclose sales data, some estimation has been necessary regarding the tonnages and values shown in Table 1. We are confident, however, that they are within acceptable limits, especially the numbers referring to natural zeolite.

Jan 1, 1979

By P. Somasundaran, A. Sivakumar

Surfactants and polymers are used in a number of processes such as flotation and flocculation. The structure of the adsorbed surfactant and polymer layers control the interfacial properties of the solid and hence an understanding of the structure of the adsorbed layers at the molecular level is essential. In this paper, a review of different spectroscopic techniques (fluorescence, electron spin resonance and Raman) used to characterize the adsorbed layers [in-situ] is presented. Information on the micropolarity, microfluidity and size of the surfactant aggregates was obtained and the growth of the adsorbed layer was followed. [In-situ] conformational states of polymers at the solid/liquid interface were determined for different pH values.

Jan 1, 1989

By Wang Zuoyu

The manuscript of this paper was not available for publication when the Proceedings went to press. Should the author elect, he may distribute copies to the time of the Symposium.

Jan 1, 1986

By S. R. S. Sastri, G. V. Rao

Because the nickel contained in lateritic nickel ores does not occur in an identifiable mineral, it is generally accepted that these ores are not amenable to beneficiation. For this reason, such ores are either directly smelted or leached to extract the nickel. In this paper, a process for enriching the nickel content of the lateritic nickel-bearing chromite overburden, normally a waste material generated during chromite mining, is described. In this flotation process, a nickel preconcentrate containing >1.1% Ni was obtained from material containing as little as 0.36% nickel. An empirical relationship was developed to predict the grade of nickel that can be obtained.

Jan 1, 1997