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By R. B. Inturi, R. G. Reddy

Solid-state reduction of roast Movat chromite ore with carbon was carried out as a function of the C/FeO ratio at temperatures ranging from 800°C to 900°C. The reduction was studied using thermogravimetric analysis (TGA). A two¬stage mechanism consisting of the reduction of FeO with carbon monoxide and the regeneration of CO by the oxida¬tion of carbon with CO2 was proposed. The rate-controlling step is the carbon oxidation reaction. A kinetic equation, that of random nucleation, was proposed. The activation energy for the reduction was determined to be 55,800 J/mole and is compared to those activation energies determined for other chromite ores.

Jan 1, 2000

By Eugene E. Brucker

In recent years, there has been increased interest in construction problems presented by karst topography. Twenty-five years ago, karst areas were by-passed for development. Today, the high cost of land and population pressures are requiring utilization of karst areas. Areas exhibiting karst features can be satisfactorily developed so that construction can proceed in a normal manner; or the areas may be left undeveloped and the underground drainage system abused by improper use causing or contributing to structural collapse, excessive erosion, and a grave threat to the stability of land development and the environment. The term "karst" is a comprehensive term applied to areas underlain by soluble rock that possess a topography formed chiefly by the dissolving of rock and the diversion of surface waters to underground routes. There are four features which contribute to the maximum development of karst. 1. A soluble rock, preferably limestone, must be present at or near the surface of the ground. Occasionally, dolomite will suffice.

Jan 1, 1970

By R. B. Coleman, T. P. McNulty

HISTORICAL PERSPECTIVE Environmental protection is not a newcomer to the minerals industry, there having been numerous examples dating from decades ago. Sometimes the awareness of a need for preservation or restoration derived from the ethics and principles of the engineers and management responsible for development and operation of a property. On the other hand, pressures to clean up industrial messes frequently were applied by special interests such as farming and ranching, recreational and conservational groups, and local governing bodies. Mineral industry environmental controls in this century have therefore been a patchwork of good intentions and bad, clean operations and dirty ones. The Hoboken siphon converter for converting copper matte while effectively capturing sulfur dioxide at a relatively high concentration was developed in Olen, Belgium in 1928, a full sixty years ago. The alternative was closure of the Hoboken smelter by Belgian government health officials who had become intolerant of sulfur dioxide emissions which were causing serious respiratory ailments in the river valley in which Olen is situated. As early as 1958, the Anaconda Company had a full-time botanist on its metallurgical research staff with the responsibility of learning how to vegetate the extensive tailings deposits at Anaconda, Montana. By that time, considerable progress had already been made in restoration of Silver Bow Creek, which at one time was “dead” for as far as 40 miles down- stream from the point of entry of acid mine drainage in Butte.

Jan 1, 1989

By Y. A. Attia, D. K. Sengupta, H. A. Hamza

Increased recycling of waste paper has been emphasized in recent years in both the United States and Canada for environmental and economic reasons. Removal of ink particles from waste paper pulp is therefore necessary. One of the most promising methods for ink removal is froth flotation. This study investigated the feasibility of a simplified flotation scheme and found that about 90% to 92% ink removal can be achieved. Also, a 95% to 97% ink removal is achievable if a hydrophobic polymer is used ahead of the flotation stage. Clean paper pulp recovery was over 90%. The effects of pulping pH, flotation pH and concentrations of flotation and polymeric reagents are discussed in the paper.

Jan 1, 1995

By Ronald J. Thomas

Prior to 1974, bauxite-producing countries were poorly informed about important aspects of the bauxite/alumina/aluminium industry. This placed them at a disadvantage in negotiations over the development of the industry with interested parties. Since the formation of IBA, its member governments have acquired a fuller awareness of the structure and operation of the industry. The role of IBA is to enlarge the relevant information base of member governments, to act as a forum for the exchange of information on the industry and to form a focal point for multilateral discussions on problems in the industry with corporate interests and with governments of consuming countries.

Jan 1, 1984

By Douglas W. Fuerstenau, Douglas M. Deason

The depletion of high grade siliceous phosphate ores is bringing about a search for economically processable replacements. The processing of unexploited dolomitic sedimentary phosphate reserves has numerous problems including the similar surface properties of the carbonate and phosphate minerals and the presence of significant concentrations of dissolved species in the flotation pulp. In this paper, inorganic adsorption and surface transformation phenomena exhibited by the dolomite/apatite systems are examined in detail. Electrokinetic, adsorption, and flotation results indicate that when placed in a common solution, these two minerals interact significantly, with a corresponding strong influence on flotation using a physisorbed collector. Such behavior can have strong implications for flotation plant practice.

Jan 1, 1993

By Otis M. Clarke

Domestic bauxite used in aluminum production comes from Arkansas where syenite was lateritized forming bauxite. Part of the residual bauxite and kaolinized syenite were eroded, deposited downdip, lateritized with bauxite formed in place, and covered by sediments. The unconsolidated overburden causes problems in mining. Bauxite for refractories and chemicals comes from Alabama and Georgia. Sediments were deposited in karst lakes and were lateritized forming bauxite and kaolin. Ferruginous bauxite in Washington, Oregon and Hawaii, derived from weathered basalt, can be used in aluminum production.

Jan 1, 1984

By Catherine M. Dentan, Yosry A. Attia

The presence of finely divided carbonaceous matter, particularly graphite, in gold ores, adversely affects the adsorption - recovery of gold by activated carbon from cyanide solutions of such ores. Competitive adsorption of gold by graphite and other carbonaceous matter, is thought to be responsible for this deleterious effect In this study, adsorption of gold cyanide complex AU(CN)2- by the activated carbon used in carbon-in- pulp or carbon-in-leach processes, was compared with that by graphite which was chosen to represent the carbonaceous matter. Similar adsorption studies were made with gold chloride complex AuC14-. Correlation of adsorption with surface characteristics and thermodynamics were presented in detail, and a flowsheet for graphite-in-leach was proposed.

Jan 1, 1990

By Gian-P. Lozej, Ross Y. Black, Sami S. Maddah

The Zabirah bauxite is a Cretaceous paleolaterite exposed by postTertiary uplift and erosion of the Phanerozoic sequence. The laterite profile, which is preserved in situ, occupies a prominent angular unconformity over a sequence of sandstones, siltstones and mudstones ranging from Late Triassic to Early Cretaceous in age, and is overlain by a Late Cretaceous terrigenous and carbonate package. The profile is known to be preserved over an area of 250 sq km and at depths below the present surface of up to 80 m. The bauxite layer is hard, compact and predominantly pisolitic, with a variety of subordinate, superimposed textures resulting from post-formation alteration. The bauxite minerals are boehmite and gibbsite. Boehmite generally predominates, and the boehmite:gibbsite ratio averages 2:1, with a marked tendency for the proportion of boehmite to increase down the profile. Kaolinite, a major constituent of the profile, is concentrated in two zones, one above and one below the pisolitic bauxite layer. Iron content is variable and bears a direct relationship to parent-rock lithology. Genesis and preservation of the bauxite are due to the favourable coincidence of a number of geological controls of which the most significant are the local structural and sedimentary regimes, the lithology and chemistry of the parent rocks, and the Cretaceous paleogeography of the region.

Jan 1, 1984

By Asa Weber

With continuing pressure from stockholders not only to maintain but to increase mineral revenues, producers have increased plant capacity. Depressed mineral prices have accentuated the trend toward higher production rates to maintain consistent cash flow, and these same trends have promoted the development of large-scale processing equipment. In addition to the need to handle increased throughput, larger flotation equipment can result in decreased capital-equipment and operating costs. The development of larger column and conventional flotation equipment relies, in part, on suitable scale-up procedures. To properly scale-up large flotation cells and columns, certain constraints and design parameters must be taken into consideration, including velocities in the vessel, residence time, solids suspension, and lip loading. This paper will review the design constraints and scale-up criteria for WEMCO® flotation cells. Scale-up criteria are augmented with computational-fluid- dynamics analyses and high-speed imaging techniques, as well as multiple regresesion analysis of in-plant operational data.

Jan 1, 1999

By R. E. Utting

INTRODUCTION Until recently, gamma doses had been largely ignored in Ontario uranium mines. This has been due to the assumption that these doses are small and have been more or less unchanged with time and hence their effects have been included automatically in the epidemiological studies that led to the establishment of radon daughter exposure limits. This assumption had to be challenged for two basic reasons. The first was that radon daughter exposures to miners have been progressively reduced over the years due to improved ventilation and ever more stringent regulations, while gamma exposures have presumably remained relatively unchanged. Therefore it must be assumed that the ratio of gamma to radon daughter exposure has gone up. The second reason is more philosophical. It is clearly inappropriate to make judgements on the significance of a potential industrial hazard when the magnitude of that hazard has not been fully assessed. Having decided that some sort of assessment of gamma exposures to uranium miners must be made, it was than necessary to determine how this should be done. Several options were available, for instance: (i) Wholesale personal gamma dosimetry for all mine and mill workers, (ii) Personal gamma dosimetry only for those workers suspected of receiving the higher doses, coupled with area monitoring to estimate the exposures of other workers, (iii) Area monitoring coupled with dose rate times time calculations for all. This would correspond to the generally prevalent method of assessing radon daughter exposures. It was argued that since radon daughter exposures are the major radiological hazard in uranium mines, to invest resources for assessing a lesser hazard to a greater degree of precision was not cost effective. (iv) Since gamma dose rate is related to ore grade, individual doses could be assigned from knowledge of work location and ore grade. Before deciding which of these options would be most appropriate, it was necessary to have some idea of the magnitude of the problem. Very few data were available in the literature and with the exception of a few spot dose rate measurements, and the results of a few gamma dosimeters issued to selected individuals by some of the mining companies, nothing was available. A rule of thumb of obscure origin is often quoted within the industry indicating that gamma dose rates underground will be about 0.25 mR/h per lb/ton or 5 mR/h per % U. This had been used by some to justify neglecting gamma radiation at least for ore grades of the order of 0.1% or 2 lb/ton, on the grounds that gamma dose rates would be of the order of 0.5 mR/h and therefore give rise to annual doses of only about 10 mSv (lrem). That is, it was assumed that gamma radiation was of limited concern compared to the hazard associated with the inhalation of radon daughters. We were thus faced with the situation of just assuming that no regulatory limits were being breached. This situation could not be allowed to continue. A program was initiated to investigate the gamma doses absorbed by uranium miners in three mines in Ontario, and extensive gamma surveys were conducted in the Quirke 2 mine of Rio Algom Ltd, Elliot Lake; Denison Mine, Elliot Lake; and Agnew Lake Mine, Espanola. Negative reaction was received from several mine company officials to the possibility of all miners being required to wear personal gamma dosimeters due to the logistical difficulties involved, and therefore part of the project was aimed at determining if a reliable correlation between gamma dose rate and ore grade in the work location could be deduced, in order that dose rate times time calculations might be used for gamma dose assessments. The results of these programs provided evidence that the gamma dose for some employees in the three mines investigated may be a significant fraction of the current maximum permissible annual dose of 50mSv (5 rem). When combined with radon daughter exposures in the manner recommended by the ICRP at their 1980 Brighton meeting (ICRP 80) the results indicated that some individuals will come close to the resulting limit and may even exceed it. The results also indicate that is probably not feasible to develop a reliable formula for

Jan 1, 1981

By Malcolm J. McPherson

Mine shafts that are used as primary ventilation routes are different in their airflow characteristics to other subsurface openings because of the aerodynamic effects of guide rails, buntons, pipes, cables, ropes, and shape, size and velocity of conveyances. As many shafts contribute heavily to the overall resistance of a mine ventilation circuit, it is important to be able to predict the resistance of a planned shaft with reasonable accuracy. This paper describes part of a study on the ventilation characteristics of hoisting shafts, conducted for the Basalt (Nuclear) Waste Isolation Program (BWIP). Methods of quantifying each of the four components of shaft resistance are developed; namely the shaft walls, fittings (buntons, pipes, etc.), the skips or conveyances, including the dynamic effects of their motion, and shaft stations. Practical guidance is given on ways of reducing the shaft resistance. The paper concludes by giving a step by step procedure for the ventilation aspects involved in the design of combined hoisting/ventilation shafts.

Jan 1, 1987

By R. R. Oder, R. J. Gray

We report measurements of the effects of rank, type, and grade of coal on grinding energy and grinding media consumption in a Pitt Mill. The rank of coal has a greater effect on grinding energy than does coal type. The effect of coal grade on grinding energy depends upon the relative grindability of the mineral matter and of the hydrocarbon components of the coal. The mineral matter is primarily responsible for abrasive media wear in a Pitt Mill. The widely recognized HGI test for coal breakage may yield misleading results, particularly for multiple-banded bright and dull coal where the screening procedure used in sample preparation favors the testing of the hardest coal fraction. The work reported here indicates that the Pitt Mill, which grinds the whole coal in a single stage and which yields easily interpreted results, is an excellent candidate for testing coal pulverization characteristics including energy requirements and equipment wear. The measurements of the effects of coal characteristics on grinding energy and on media consumption have been used to estimate the cost of fine grinding in a Pitt Mill. The results, based on a conceptual level evaluation of grinding at the rate of 1 TPH, show that there are trade-offs possible between the cost of energy and cost of media consumption which involve choice of grinding media size. The use of fine-size grinding media to lower grinding energy and to increase throughput can be deceptive because the total cost of grinding must consider both energy and media consumption.

Jan 1, 1992

By R. Y. Wan, J. R. Parga, J. D. Miller

The direct recovery of precious metals from a1kaline cyanide solution is frequently accomplished by the well-established Merrill-Crowe process involving zinc-dust cementation. This is particularly true for silver. Plant data from two operations are presented and analyzed in terms of intrinsic reaction features. In such Merrill-Crowe plants a plate-and-frame filter press acts as a semicontinuous fixed-bed reactor with a distribution of particle retention times. For the plants studied, 99Yo of the silver is recovered with a solution retention time of less than 2 min. Differences in plant operating conditions and product characteristics can be related to the nature of the surface deposit of silver which forms on the zinc particles. From laboratory experiments and plant samples it has been found that the presence of lead in the system activates a change in the silver deposit morphology to the dendritic state which affects the rate of silver deposition as well as the filter cake porosity. Finally the plate-and-frame press is considered from an engineering perspective as a semi- continuous fixed - bed reactor to describe the behavior of the system.

Jan 1, 1987

By William G. Fischer

Equations developed by an early researcher in subsidence, F. Martos of Budapest, Hungary, have been slightly modified to produce effective equations for predicting the time-dependent nature of Green River trona mine subsidence. Following the initial study, a survey was run to check the results twenty years after mining of the area had been completed. The final results were within a few centimeters of the value that had been projected. Mining conditions in the Green River area are ideal for this sort of study with trough type subsidence being the surface manifestation of high extraction underground room and pillar caving operations.

Jan 1, 1986

By Ryota Kasahara

In 1981, a gas outburst accident occurred in the Yubari Shintanko coal mine, the only expectant mine in Japan, it caused 93 deaths. As a result, Yubari Shintanko closed in 1982. This major disaster was a turning point for sustainability of Yubari City, the largest coalfield in Japan. Finally, Yubari City was bankrupted in 2007. This paper aims to explore how miner’s children experienced this disaster and felt about region, family, and themselves, and to explain the relation between region declining and children’s lives. The data of this paper are the archived 600 essays, written by the junior high school students at the time of the disaster. There are three findings. First, the children who lost their father were the most shocked. They faced profound sadness. But they expressed that they had decided to overcome their sadness with surviving family. Second, the children who didn’t lose their father were also influenced. They were anxious about the future of Yubari, their family, and themselves. Furthermore, they decided to strive for their future. Third, they understood the disaster as a turning point of Yubari declining and looked ahead their future outside of Yubari. In conclusion, this disaster created their hopelessness to Yubari region and, as a result, promoted the decline of the city through their migration to other city. Furthermore, it is important to clarify that Yubari City has to continue the struggle to the regeneration.

Jan 1, 2017

By Daryl R. Tweeton

The Bureau of Mines has developed PC-based tomographic computer programs for geophysical applications, and is making them available to potential users as part of a Bureau plan to facilitate the transfer of technology to industry. These programs were initially developed for predicting and monitoring the flow pattern of leach solution during in situ mining. Seismic crosshole tomography has located fractured zones of low seismic velocity and saturated zones of high seismic velocit above the natural water table. The Bureau has applied tomography also to assessing high-wall blast damage, and examining the integrity of mine-related geological structures. The tomographic programs include the straight ray pro ram BOMTOM (Bureau of Mines Tomography? and the program BOMCRATR (Bureau of Mines Curved Ray Tomographic Reconstruction) that can be run with either curved or straight rays. Both programs provide optional mathematical constraints to help counteract the nonuniqueness of reconstructions that occurs with crosshole data. They are available from the Bureau free of charge. With typical data sets, they can be run on a 386 microcomputer with 640 Kb RAM. BOMTOM was described in the Bureau Report of Investigations 9159, so this report emphasizes BOMCRATR. Curved and straight ray reconstructions using seismic field data collected while simulating injection of leach solution were compared. The curved and straight ray tomograms were quite similar even with velocity variations of more than 50 percent.

Jan 1, 1992

By Richard H. Sailors

Data from full scale marked ball tests are used to demonstrate the effects of abrasion, corrosion, and impact on overall wear rate. The predominate wear mechanism need be identified before the optimum alloy can be chosen for the grinding media. Use of high chromium grinding media often results in increased mill efficiency due to shape retention. Thus, a benefit from energy savings can result as well as a reduction in wear rate. Converting from steel to east high chromium grinding media requires close association and cooperation between producer and consumer in order to properly conduct these studies.

Jan 1, 1990

By A. J. Abraham, K. E. Seitz, J. D. Humphrey

Caterpillar has led the way for sound reduction in off highway trucks (OHT) used for mining. In 2000 Caterpillar introduced the 793CXQ sound reduction OHT (Figure 4) to meet local noise level demands in the Hunter Valley near Sydney, Australia. The sound level of the mining equipment in the Hunter Valley is being reduced to pre-serve the quality of life for the residents of the area. To meet the levels established required a major redesign of the 793C, as a result the sound power level was reduced by 9 dB (A), which is a less than 1/8the original sound level.

Jan 1, 2004

By R. C. Babcock

Exploration for mineral deposits in the western United States is increasing annually, and the data generated by this effort are increasingly complex, diverse, and abundant. It is obvious that to make full use of this data base, which is both private and public, the technology of the computer must be involved. To lay out the framework for discussion of the particular uses of computers in all steps of exploration, this chapter will discuss the various approaches to the reconnaissance program which might be considered, the types of data to be acquired, the interpretation of these data, and the generation of recommendations based on this interpretation. Where possible, some of those areas where computer technology is now used will be pointed out. The discussion will cover the extent to which the computer is now utilized in those areas or where it should be brought into the program to aid in these activities. However, this chapter will not present an exhaustive evaluation of this technology, but will stress the exploration job and its requirements, so that subsequent discussion of the technology itself can be placed in perspective.

Jan 1, 1979