Search Documents

By Raymond E. Kary, John W. Mcklveen

The four unit Cholla coal fired power station at Joseph City, Arizona, consumes coal from the McKinley mine located in western New Mexico. Since coals may contain relatively high uranium or thorium concentrations and may release quantities of detrimental progeny of these elements to the environs, there is concern that releases may pose an adverse environmental impact or even a health hazard to the workers. Thus, an effort was made to quantify the radionuclide content of the coal and compare the results with radionuclide concentrations already present in the vicinity of the plant. Additionally an attempt was made to assess any potential for significant enhancement of the levels of radioactivity in the environment or to plant personnel. Background gamma radiation measurements at and near the plant ranged from 8 to 12 [µ]R/hr (70 to 105 mR/yr) with a few localized anomolies measuring to 18 [u]R/hr (160 mR/yr). Levels on top of the coal storage piles decreased to ~ 6.5 [u]R/hr (60 mR/yr). Apparently the direct radiation emitted from the coal is less than the background levels in the vicinity of the plant. Measurements performed on top of several coal seams at the mine confirmed low radiation levels emanating from coal, but readings more than doubled when the overburden was monitored. Laboratory gamma spectrometry confirmed the lower amounts of natural radioactivity in the coal when compared against soil and water samples obtained in the vicinity of the plant and the overburden at the mine. In an effort to see if there is biological enhancement, animal feces was sampled. The radiation variations were found to be influenced primarily by naturally occurring potassium-40 which varied from ~ 1 to 18 pCi/gm rather than fluctuations in the uranium and thorium series. The potassium-40 concentrated in the ash were similar to the concentrations in the environs around the disposal ponds while Radium-226 concentrated in the fly ash was ~ 3 times that found in the immediate surroundings. Radon-222 gas concentrations in buildings at or near the plant ranged from 0.5 to 1.8 pCi/l and were generally lower than indoor concentrations measured in the Phoenix area. The burning of coal at the Cholla station does not appear to increase ambient levels of radioactivity found in the surrounding environs or to the workers. However, the use of byproduct fly ash for construction purposes may need to be examined.

Jan 1, 1981

The first of this two part series takes a look at some of the history and types of flotation as well as agents and mechanisms involved in it. Part two, next month, will examine flotation processes as applied to various sulfide and nonsulfide mineral ores. Flotation-"froth" flotation-is a physicochemical method of concentrating finely ground ores. The process involves chemical treatment of an ore pulp to create conditions favorable for the attachment of predetermined mineral particles to air bubbles. The air bubbles carry the selected minerals to the surface of the pulp, there forming a stabilized froth that is skimmed off and from which the predetermined mineral particles are recovered. Other minerals remain submerged in the pulp.

Jan 3, 1982

By Jacob Petersen, Jon J. Kellar, Samuel Kessinger, Kiran Green

 The paper demonstrates that Belle Fourche Shale (BFS), an abundant shale, can be transformed into a ceramic through careful characterization and thermal processing. The study explores the potential of BFS ceramics for use as refractories and thermal energy-storage devices, highlighting their high thermal storage capacity, good thermal shock resistance, and cost-effectiveness.

Dec 1, 2023

By Roger Mourich

As the Powder River Basin coal industry has grown, many changes have occurred in the coal market, the economy and the Basin's methods of dealing with competition in the coal mining business. This article notes the mines that have changed to draglines as the major overburden-stripping tool. The Powder River Basin is defined as those mines within a 97 km (60 mile) radius of Gillette, WY. Mines to the north and south of this area - Decker, Spring Creek, Glenrock - have used draglines more extensively. The reasons for the conversions to draglines at each mine, and the specific timing of these changes, were different. However, the driving factor was economics. As coal production increases, strip ratios increase and coal sales prices decrease, mines must find ways to deal with rising costs and falling revenues. The primary method used has been conversion of overburden stripping to dragline operations. Stripping ratio equals the bank cubic yards of overburden removed for every ton of coal mined.

Jan 1, 1994

By Karl-Heinz Bruemmer, Karl Wollers

1- Importance of Shafts for the Exploration and Extraction of Coal Deposits Coal mining in the Federal Republic of Germany is carried out in a depth between 800 and 1200 m below sea level (Fig. 1). The shortest connections underground in a mine and up to the surface are vertical shafts. Such shafts assume, with ventilation, manriding and the winding of material, the most important functions for the maintenance of mining operations. In the German coal mining industry, a difference is made between the main shafts providing a direct access from the surface to the deposits, and the so-called "blindshafts" which serve as a connection between two or several haulage levels underground. [ ]

Jan 1, 1976

By L. F. Delgado

Environmental and cost pressures sparked renewed interest in gravity separation. Industrial sands in Mexico are generally processed by screening, desliming, and flotation. Gravity separation with spirals was evaluated as an alternative to flotation in order to lower operating costs and decrease water pollution. Outstanding operating results are obtained in glass and foundry sand operations, plus a more competitive position for Mexican producers due to lower operating costs. Coal fines, generally recovered by flotation, have the same cost and environmental advantages when processed with spirals.

Jan 1, 1994

By William A. Holgate

Coal production in the in the Powder River Basin began its tremendous expansion during the boom of the mid-1970s. New mines were opened from 1976 through the early 1980s. This expansion soon placed Wyoming at the top of the list of coal producing states, where it has since remained. Mines are operated by large companies, with safety and production having equal priority. These mines have been some of the safest ever in the coal industry. Many Sentinels of Safety Awards have gone to them. Safety programs are varied, but there are commonalities. Mine safety at Wyodak Extra training is required of all supervisors. The company offers to pay for any additional first-aid training that employees participate in. Safety departments conduct weekly safety talks. All employees receive the monthly magazine Family Safety and Health compliments of Wyodak. Electricians receive extra training on electric wheel motors, from General Electric. Equipment operators receive extra training from Dresser.

Jan 1, 1994

By R. S. C. Rogers

Semiautogenous milling was the subject of 18 papers presented at the SME Fall Meeting in Albuquerque, NM. The process design and scale-up of SAG mills was discussed in several papers. These included a review of testing methods for the sizing of SAG mills by Barrett and Allan. Austin et al. presented an improved simulation model for SAG mill grinding, with model validity demonstrated against pilot plant SAG mill test results. Rogovin et al. presented some pilot plant results relating to the charge motion, hold-up, and particle size segregation in SAG mills. A number of papers described improvements achieved in operating SAG mill circuits. These included presentations by Dailey concerning mills at the National Steel Pellet Co., by Brown and Pipke concerning the Island Copper grinding circuit, by Lovering of Afton Mines Ltd., and by Bartrum et al. of Kidston Gold Mines Ltd. Bush and Hegerle of Amax also discussed SAG mill operations at the company's Henderson mill. They addressed the topics of SAG mill grinding economics. Other papers addressed the topics of SAG mill control (Vanderbeek et al. and Pennington), grinding media (Meulendyke et al.), liners (Kjos), and fabrication (Carr and Utley). The 1985 AIME Annual Meeting in New York featured four technical sessions concerning size reduction technology and practice. Papers involving fundamentals included one by Hinde describing simulation model usage for quantifying the classification and concentration of heavy minerals in grinding circuits. Another, by Rogers et al., discussed simulation models that were used as a design aid in evaluating screens versus hydrocyclones for fine grinding circuits. Arbiter discussed dimensional considerations in grinding mill design, and Schwechten and Schonert proposed the use of a high pressure roll mill as a means for reducing energy requirements in fine grinding. Internal classification in tumbling mills was the subject of a paper by Hogg and Rogovin. The mechanism of internal classification were identified and their effects illustrated. Simulation for the process design of ball mills was exemplified in a paper by Rogers, Austin, and Brame concerning phosphate grinding in laboratory to large diameter mills. The incorporation of liberation into size reduction models was the subject of papers by Austin et al., Herbst et al., and Choi et al. Gupta used simulations models to further investigate zero order fines production in ball and rod mills. Of the published literature, many articles on size reduction were published in various publications in 1985. Articles concerning ball mill grinding included an analysis of interstitial gas effects in dry grinding by Cottaar et al., an analysis of mill grinding noise by Watson, studies of factors affecting breakage rates in dry milling by Gupta et al., and in wet milling by Tangsathitkuchai and Austin. Austin and Klimpel presented two papers concerning ball wear and ball size distribution effects. Koka et al., and Gotsis et al., described recent developments concerning the Szego mill. A model for hammer milling circuits was described in papers by Gotsis et al. and Gotsis and Austin. Heim et al. reported on wet grinding in Perl mills, and Kuga et al. presented findings concerning pulverizing in a screen mill. Studies of grinding effects on particle surfaces were published by Meloy and Hofmann et al., and Scieszka proposed a technique to investigate pulverizing properties of coals. Austin and Rogers discussed factors of powder technology of significance in industrial size reduction in mills and crushers. (Space limitations preclude listing of references. A complete list is available from author.)

Jan 5, 1986

By Merwin Bernstein

Peru has been an important source of metals since Aug. 29, 1533. On that day Francisco Pizarro took charge of the 24 t (772,000 oz) of gold and silver that constituted Atahualpa’s ransom. At today’s prices, the value of that booty ranges between $100 and $150 million, depending on the proportion of gold to silver. Since then, Peru’s silver and gold production has been legendary. Current mine production Most of Peru’s metals are mined from the Andes Mountains and its foot-hills. The Andes run the length of the country parallel to the Pacific coastline from Ecuador to Chile, a distance of nearly 3000 km (I 875 miles). They are about 300 km (187 miles) wide and much of the range is more than 3000 m (9900 ft) in elevation. High plateaus (altiplanos) occupy a large part of the range. Both flanks are rutted by large valleys and canyons. Many of these peaks are prodigious. which make road building expensive and adds to the cost of mining.

Jan 1, 1993

By Brian H. Kaye

Efficient design of grinding circuits for efficient production of ultrafine material requires rapid feedback of information concerning the fineness of material leaving the grinding device Generating this information requires efficient sampling and adequate rapid characterization of the material leaving the grinding machinery Recent developments in electrooptic inspection of dry and wet material leaving a grinding device are critically reviewed New methods for characterizing ultrafines are discussed A rapid operating automated cybernetic (intelligent) permeability device for automatic control of grinding circuits using Blaine Index and other fineness indices is described

Jan 1, 1983

By S. Nickson, M. Grenon

Oriented borehole data provide the means to characterize a rock mass. In this paper, the geomechanical caving potential of a hard rock mine project is investigated. In particular, the influence of random joints to the resulting block size distributions is addressed. The implications of this approach in preliminary investigations on the choice of mining methods are discussed with reference to one site.

Jan 1, 2003

By Dan G. Wasyluk, Meryl J. Klassen, Tony J. Morris, Clive H. MacKay

The Rogers Pass Project in British Columbia has involved the construction of two railway tunnels totalling 16.6 km and a 345 m deep shaft. Systematic geological mapping was carried out at four headings during construction. The paper discusses the procedures used to record the geology, structure, rock mass characteristics and excavation performance. Coded data from the geological mapping and shift inspector reports was entered into a computer data base. The rock mass quality was evaluated for both the Geomechanics and Q classification systems. Continuous computer generated graphic logs were produced showing the excavated perimeter map, geological parameters, installed support and construction activities. The tunnel logs were updated on daily basis and used during construction by project staff for evaluating support requirements and monitoring excavation progress. The specific requirements, difficulties and advantages in mapping tunnels using a computer based system are compared to those of a conventionally mapped tunnel excavation with hand drafted tunnel logs.

Jan 1, 1987

By James Wm. White

Mine management now recognizes the value of computer-based truck-shovel dispatching in open pit mines. The key tangible benefits are substantial productivity increases with a given fleet of equipment or, alternately, significant reductions in equipment required to meet production quotas. In this work, we review the literature, report on efficient, optimal algorithms for haul truck dispatching in real-time, and briefly discuss methods used by various mines to evaluate productivity improvements over manual methods. We also present actual results obtained at thirteen mining operations around the world.

Jan 1, 1992

By F. F. Aplan, V. Choudhry

This investigation is an exploratory study to evaluate a large number of potential pyrite depressants for use during coal flotation. Subsequently, the more promising reagents can be evaluated in detail. Several reagent categories (such as alkalis, lime, oxidizing agents, reducing agents, specific inorganic ions and dispersants) that were found to be effective pyrite depressants are discussed here. Other pyrite depressants will be discussed in Parts II and III.

Jan 1, 1993

By A. Covelli, A. B. Cecala

Two recent US Bureau of Mines studies evaluated workers' dust exposures in automated pallet loading processes. The first study involved a Bureau designed dust control system using a push-pull ventilation technique. The unit was shown to reduce workers' dust exposures by 76% during pallet loading at a ground silica operation. A hydraulic lift table was used to automate the bag stacking process. This kept the loading height constant throughout the entire pallet loading cycle. The second study evaluated different commercial, automated-pallet loading systems. These systems automatically stack the bags onto pallets, shrink wrap the pallets, and deliver the pallets to a fork lift pickup location. Results from a ground silica evaluation site indicated respirable dust samples taken were below the Threshold Limit Value (TLV) as established by the Mine Safety and Health Administration (MSHA).

Jan 1, 1992

By C. Strachan

This paper presents an evaluation of the tailings dam incidents included in the 1994 US Committee on Large Dams (USCOLD) Committee on Tailings Dams report. Also, comparisons are made to water storage dam incidents from USCOLD reports, as well as to more recent tailings dam incidents. The evaluation results show that tailings dam incidents result from a number of factors, including overtopping, static and seismic instability, seepage and internal erosion, and foundation conditions. The results also show that no particular type of tailings dam or operational condition is more susceptible to incidents. In addition, the results confirm that tailings dams should be located, designed, operated and reclaimed with a thorough knowledge of site conditions, mill operation, site monitoring and tailings characteristics.

Jan 1, 2002

By I. J. Lin

We have studied the possibility to use electrical phenomena in order to selectively separate minerals with various densities and dielectric constants in non-homogeneous electric fields. This technique is based on levitation forces acting on a solid particle immersed in dielectric fluid. When the gradient of the electric field is directed downwards, the levitation force in the dielectric fluid (pure liquid or electric colloids) will be in an upward direction to float sinking minerals by counterbalancing their density mismatch with the liquid medium. The separation process can be made by using two possible modes: either by direct application of electrical forces or by change in the density and dielectric constant of a liquid medium in which the mineral particles are placed. We have investigated several electrode configurations in order to produce electrical fields which are strongly non homogeneous. Further more, investigation on the dielectric properties of liquids have been performed.

Jan 1, 1977

By Jean-Claude Bianchini, Paul Bauernfeind, Erwin Gartung

Introduction The city of Nuremberg, located in Bavaria in the Federal Republic of Germany, started building a subway in 1967. The construction operations began in a southern suburb, where no complications were encountered in the design and execution of the job. As the first subway line approached the downtown area of the city, the civil engineering challenges increased rapidly. Tunnels had to be excavated next to, or below precious historical buildings, and the work of the responsible engineers was closely watched by the public, who were very anxious about any damage to the existing beautiful old houses and churches. The job has been handled successfully to date in cooperation with the owner-designer, the geotechnical consultant and the contractors, who jointly went through a process of systematic learning and gathering of experience, and who developed a modern tunneling technique specifically tailored to the natural properties of the encountered ground conditions and the requirements of the city of Nuremberg. The application of scientific methods has been an important part of this development. Research into the geotechnical properties of the predominantly encountered soft Keuper sandstone, studies of the geomechanical performance of grout reinforced sand sections and finite element analyses of various tunnel problems for the prediction of displacements, for the assessment of stability, or

Jan 1, 1979

By E. R. Braer, C. J. Bise

The trend in underground room-and-pillar coal mining is to employ remote-controlled, continuous-mining machines and extended cuts to depths of 12 m (40 ft) or more. This system of coal extraction, adopted by more than 435 mines, can create additional worker safety hazards. To address the ground-control-related safety hazards, a combination of statistical analysis and numerical modeling was used. Initially, the reported roof-fall incidents and fatalities were reviewed to delineate the ground-control hazards. Then, the application of the coal mine roof rating (CMRR) for estimating safe extended-cut depths was evaluated. Finally, computer modeling was completed to predict roof displacements during extended-cut mining. This paper describes the results of these studies and their impacts on the safety of extended-cut mining.

Jan 1, 2000

By Bart Hogeweg

The development of deep sea mineral deposits creates a new horizon for the mining industry. In a field where mining technology meets deep-water offshore engineering, new challenges are faced to come to the successful exploitation of these deposits. With the absence of proven technology for the mining of these minerals, a ?technological green field? is entered. IHC Merwede (IHC), a global market leader in the dredging and wet mining industry, is on the frontline of these developments. MTI Holland, IHC Merwede?s research and development company, has undertaken a number research efforts focused on the successful development of technology for the mining of deep sea minerals. This paper highlights a number of these efforts and illustrates IHC?s continued dedication for the research and development of technology to enable the commercial mining of deep sea minerals.

Jan 1, 2008