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By B. S. Treiber, R. A. Lohnes, S. M. Levorson

As part of a research program to develop a coal-handleability index that would predict the ease with which a coal would flow through a handling system, an apparatus was developed to directly measure the unconfined Yield strength and bulk density of consolidated-coal samples. The new test apparatus provides a fast and simple method for determining the strength and compressibility parameters that are associated with the handling characteristics of crushed coal. Comparative tests were conducted using a low-stress triaxial-test apparatus. To check the accuracy of the new method, four coals with a variety of moisture contents and gradations were tested using the new method. These tests indicate that the new test device yields valid results. Further, the speed and ease of operation of the new device makes it suitable for quality control and quality assurance in plants.

Jan 1, 1996

By P. R. Dugan

Sulfur removal from high sulfur coal has several objectives including: a) reduction of the atmospheric load that contributes to the problem of acid precipitation; b) reduction of ash, which contributes to decreased energy transfer in boilers, as well as ash disposal; and c) alleviation of the social and economic dislocations related to uneven geographical distribution of sulfur in coal reserves. Cost in relation to the value of refined coal will govern the development of an emerging coal refining industry. Estimation of the premium paid by power companies for coal with a low sulfur content is a good estimate of the value that will be added as the result of refining. Estimates of premiums paid in 1984 are $28.65/t ($26 per st) for reduction of total sulfur from 370 to 1% S and greater than $28.65/t ($26 per st) for removal below 170 sulfur.

Jan 1, 1988

By G. Wonnacott

A model for simulation of gravity regrinding circuits is presented. The model can predict "secondary" density distribution data from a series of "primary" grind/density distribution tests. Thus middlings regrind requirements can be predicted from primary grind data. Traditional methods of regrind design involve lengthy and tedious tests programmes. The model presented herein can considerably reduce the quantity of testwork required for regrind design. The model can also be used to design primary gravity grinding circuits. A parameter estimation scheme and experimental data validating the model are presented.

Jan 1, 1989

By M. J. Meulendyke, J. D. Purdue

Within the mineral processing industry, a range of grinding conditions exists which include semiautogenous grinding (SAG),rod milling, and conventional ball milling. Each of these mill environments presents a unique environment for grinding media, requiring the application of specific physical and chemical properties for optimum grinding media performance. The environments are characterized by varying degrees and combinations of abrasive, corrosive, and impact wear. An extensive test program has been conducted to determine the extent wear rates vary between these different applications. Test results are related to production results, ball size, and mill operating conditions.

Jan 1, 1990

By E. T. Balazs

Share of developing countries in world bauxite resources mining and processing. Technical assistance of the United Nations Industrial Development Organization to the developing world in the field of bauxite evaluation and processing. Review of selected projects of bauxite research and development aimed at creating indigenous capabilities in developing countries: "Assistance to the bauxite aluminium industry of the People's Republic of China". Project activities. UN inputs. Achievements. Follow-up. "Upgrading the scientific and technological capabilities of the Jamaica Bauxite Institute". Project activities. UN inputs. Achievements. Expected follow-up. Assistance to the establishment of an "Aluminium research, development and design centre" in India. Project activities. UN inputs. Achievements. Follow-up. "Establishment of an aluminium institute for research and development in Titograd, Yugoslavia". Project activities. UN inputs. Achievements expected. Second UNIDO group training on bauxite evaluation and processing to alumina October - November 1983 in Budapest, Hungary. Programme and coverage. Show of movie picture on organization and execution (15 minutes). Significance of UNIDO's assistance to the developing world in bauxite research and development. References.

Jan 1, 1984

By B. C. Cornilsen, X. Shan, D. H. Carlson, J. H. Johnson

Airborne respirable Diesel Particulate (DP) presents an additional health hazard in that it has been shown to be mutagenic. This problem is of increasing concern as more coal mines introduce diesel vehicles. If the DP present in coal mine air is to be controlled it must first be measured. This paper describes development of the laser Raman spectroscopic measurement of the amount of DP in DP/coal mixtures collected on filters in the laboratory and in coal mines. The Raman technique provides a chemical measure of the carbonaceous material in each component, and is not dependent upon particle size. When this work was begun there were no known analytical methods for this measurement. Side-by-side in-mine comparisons of the results obtained from Raman, neutron activation analysis, and size selective analyses (MOUDI and personal samplers) are presented. The neutron activation and size selective analyses were obtained by the USBM Twin Cities Research Center and University of Minnesota. Good agreement has been found among these three methods.

Jan 1, 1991

By C. Mermiris

Bauxite ores in Fokida belong to Parnassus-Giona zone and are found exclusively in limestone in two bauxite horizons, which are of great economic importance and with very unfavorable conditions for the reclamation process. The ore bodies are usually less than two million tones. They are in many cases encountered near the surface as a result of the erosion and are exploited either with open pit or underground methods. Mining activity, which dates back 70 years, causes many changes to the environment and most of all to vegetation and landscape. The first step to mining exploitation of bauxite ores is the selection of an underground or open pit method taking into consideration mostly economical and technical criteria. Open pit exploitation, which causes the most severe environmental consequences, is done with the method of vertical benches in hard rock with the use of explosives. The impacts on the landscape that result from the method of vertical benches are: ? The front of the excavation that is usually solid rock of the hanging wall (limestone). The height of the benches varies from 10 to 20 meters and the gradient of the final slope is designed to be around 65o, unless the rock is not so stable and the gradient is reduced accordingly.

Jan 1, 2002

By A. J. Surtees, M. P. Evans

This paper discusses the development and application of sophisticated monitoring equipment used to measure the operating parameters of conveyor systems. With the radical reduction in price of computer hard- ware and software during the last decade and an associated increase in memory capacity, the concept of continuous conveyor monitor is now a reality. With this tool, the various problems normally encountered in large conveyor installations can now be avoided at an early stage. • The four main areas of application are: • Design verification • Hand-over certification • Preventative maintenance and increase of system availability Failure analysis The paper introduces the techniques used and gives examples where the service has been used.

Jan 1, 1996

By John E. Urosek, Herman Schade

In March, 1988, a fire occurred in a large underground coal mine. Coal Mine Safety and Health of the Mine Safety and Health Administration was immediately notified of the situation. They requested the assistance of the Pittsburgh Health Technology Center (PHTC) to provide monitoring and analysis of the mine atmosphere in and around the fire area to insure the safety of the miners escaping from the mine and for the miners involved in extinguishing the fire. The capability to provide this type assistance is maintained by the PHTC Offices located at 4800 Forbes Avenue, Pittsburgh, Pennsylvania. The equipment used is maintained field ready and can be mobilized almost immediately. This paper will discuss the response to this recent major mine fire.

Jan 1, 1989

By R. Corriveaau

This paper is about a horizontally curved conveyor, which carries 6,050 stph of limestone over land from a new quarry to the owner's plant. The conveyor is 5,012 ft long with a horizontal curve radius of5,OOOft Site conditions made a curved conveyor design the most optimal and economic solution. Using our unique custom conveyor calculation program, TKRI was able to accurately model and design the conveyor to properly track the belt and prevent any spillage through the horizontal curve radius. A data monitoring system was installed that allows monitoring of the conveyor both locally and remotely. The remote monitoring allows TKRI to contact the owner for preventive maintenance. Preventive maintenance can reduce the conveyor downtime during normal operating hours.

Jan 1, 2004

By Leo Langland

One of the primary functions of the Geotechnical Services-Materials section of the Arizona Department of Transportation (ADOT) is locating, sampling, and evaluating potential aggregate deposits throughout the State. This information is essential in designing, estimating, and bidding highway construction projects. The nature of materials used for aggregate varies greatly within Arizona. The northeastern or plateau section is famous for its scenic sedimentary formations that are, how- ever, too soft to make suitable aggregate. Volcanic materials are widely used in place of more conventional geologic units. In contrast, the southwestern, or Basin-and-Range section, contains a relative abundance of good aggregate, especially a diversity of gravels. The paper will review the off ice, field, and laboratory methods used by the ADOT Materials Section in satisfying its needs for aggregate information in Arizona.

Jan 1, 1987

By E. D. Goddard, D. S. Murphy

Acid resistance, zeta potential and ESCA (electron spectroscopy. for chemical analysis) experiments were performed on emperador marble and four calcium carbonate samples (onyx calcite, travertine calcite, Iceland spar calcite and aragonite). Six fluorine-containing reagents were used to treat the surfaces of these materials: magnesium hexafluorosilicate, zinc hexafluorosilicate, sodium fluoride, zinc fluoride, strontium fluoride and stannous fluoride. The acid resistance of treated samples proved to be much higher than that of their untreated equivalents. The isoelectric point of treated samples approaches the isoelectric point of fluorite. Also, the fluorine content, as measured by ESCA, of a marble surface treated with magnesium hexafluorosilicate is much higher than that of an untreated sample. The binding energy off of fluorine and calcium the treated marble is consistent with the formation of calcium fluoride.

Jan 1, 1994

By Mark R. Stanton

Geochemical and mineralogical analyses of 46 samples from six drill cores in the Mayday mine pile near Silverton, Colorado, demonstrate wide variability in trace metal contents with spatial location. This variability results from the original geochemical composition of mined rocks, mixing of ore and non- ore rocks during emplacement of the pile, and weathering since rocks were placed in the pile. Weathering reactions are controlled by factors such as pile thickness (depth), water availability, microbial activity, and mineral dissolution and formation kinetics. These factors result in variable redistributions of trace metals from primary (ore) to secondary (weathering products) minerals within each core.

Jan 1, 2000

By E. William Rossi, Audrey F. Glowacki, Richard L. Unger

The U.S. Bureau of Mines has developed a graphics-based computer model to assess operator visibility for continuous miners, shuttle cars, and scoops. Using digitized drawings of the machine, the program can analyze visibility for both 5th percentile female and 95th percentile male operators. This model was used to predict 95th percentile male operator visibility for two shuttle car designs. These results were then compared to those obtained from a manual assessment of visibility using the actual shuttle cars. The methods showed good correlation except for several cases which were attributed to imprecise digitization of the machines.

Jan 1, 1992

By John R. Marks

Few if any mines in North America have used exhaust air to remove heat at temperatures above the stope reject temperature. In contrast, the South African mining industry has long taken advantage of this heat removal method. The Homestake Gold Mine in Lead, South Dakota, has reached the point where a large air-conditioning upgrade is needed. Since existing air and water resources are being utilized about as well as practically possible, it was recently decided to install an 8.1 MW(R) (2300 ton) plant in the deepest mining division. Two horizontal bulk air spray coolers will distribute the coo1th to active workings via controlled recirculation. The heat will be rejected to exhaust air in four parallel cooling towers. The number and size of these large direct-contact heat exchangers prompted an investigation into South African planning techniques.

Jan 1, 1987

By C. J. Pritchard

Productivity improvements reduced the number of continuous miner sections from seven to three while maintaining full productive capacity. So a decision was made to test an advancing tailgate ventilation system on the shortwall mining section. Having the shortwall mine its own return air system has freed the third mining section for more productive, less costly mining. The advancing tailgate has provided effective ventilation across the face and gob with acceptable pressure losses. The low-productivity, tailgate-development, continuous-miner section has been transformed into to a high-productivity, development-retreat section that is also available for long-term mine development duties, increasing mine planning flexibility.

Jan 1, 1991

By K. N. Han, K. Peri, Y. Guan

The leaching behavior of gold in ammonical solutions with iodine as an oxidant was investigated using cyclic voltammogram and Tafel polarization. The majority of the experiments were carried out at 75°C, and the results were compared with consideraton given to the equilibrium of the iodine-ammonia system. The distribution of nine iodide-containing species at various pH values in the absence and presence of ammonia were considered at three different temperatures. It was found that, with the introduction of ammonia into the system, the concentration of iodide (I-), iodine (I2) and triiodide (I3-) is increased substantially, which in turn helps the rate of gold dissolution. The apparent activation energy was found to be about 46 kJ/mole, indicating a chemical-controlled mechanism.

Jan 1, 2002

By Don W. Murphy, Don M. Larsen

Advanced process control has been implemented at the Jerritt Canyon Mill. Plant production prior to 1997 was limited by grind circuit capacity. The installation of additional mill horsepower and an optimizing supervisory control system achieved a throughput increase in excess of 12 percent. The controller application utilized a seamlessly integrated fuzzy logic expert system for real-time mill control coupled with a neural network predictor for closed-loop feedback of particle size constraints. In late 1998, a second supervisory controller was installed to operate the fluidized bed roasters. The second controller optimized roasting conditions, increased plant throughput and improved metallurgical recovery.

Jan 1, 2000

By Photios G. Ioannou, Guillermo F. Salazar, Herbert H. Einstein, Yeong W. Kim

The MIT tunneling group has developed, over the past decade, a number of decision support tools for the geologist and engineer, planner and designer, owner and contractor involved in underground construction. These computer based tools can be used in the planning and exploration stage of a project, in predesign and design, in construction planning and during construction. Tasks as different as optimizing information collection during exploration and during construction, as selecting major design alternatives in predesign and modifying design during construction, as providing cost and time estimation and considering social and physical environmental constraints, can be handled. Output can be in the form desired by the user ranging from geologic profiles (cross sections) to management reports.

Jan 1, 1987

By Tim O’Neil

Many mining companies try to fight their way up from small operator and exploration company to major producer. Not many companies make it. Cambior Inc., formed in 1986, is one company well on its way to making it as a major operating company. In 1993, Cambior surpassed 15.5 t (500,000 oz) of gold production and began operations at its world class Omai gold mine in Guyana. At the same time, the company has embarked on a program of geographic and minerals diversification. Cambior, a Canadian company, now has interests in eight mines, three development projects and more than 100 exploration properties in North and South America. The company’s goal is to derive 70% of its income from gold and 30% from base metals and other minerals. Cambior’s moderate diversification into base metals gives protection against negative gold price fluctuations. It also balances the typically short term gold mines and the longer term base metal mines.

Jan 1, 1994