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By B. Anameric

Considerable effort has been directed towards understanding the carbothermic reduction mechanisms of self-reducing, fluxing dried green balls to produce pig iron nuggets. Given the geometry of the situation, some investigators believed that the shrinking core model was applicable. Hence, this study involved investigation of the applicability of the shrinking core model to pig iron nugget production. The experiments involved heat treatment of dried green balls utilizing either a laboratory-scale resistance box furnace or a gas-fired muffle furnace at various furnace temperatures and residence times. The products were analyzed for the following: (i) preferred reaction pattern, (ii) distribution of the metallized areas, (iii) % iron content variation in the pig iron nuggets from surface to center, (iv) carburization pattern and (v) physical and chemical properties of the pig iron nuggets. It was determined that the reduction of iron oxide occurred simultaneously throughout the sample and not beginning at the surface and propagating inward; thus the shrinking-core model was not applicable. Heat transfer and gas diffusion from surface to center were not the rate-limiting steps for reduction and carburization reactions.

Jan 1, 2011

By R. S. Shoemaker

Environmental and regulatory authorities are increasingly requiring that precious metals heap leach piles be contoured before they are abandoned so they may present a more "natural" look to the eye. Depending on the ore type, many of these contoured heaps will be subject to substantial erosion by precipitation events, native plants will have difficulty in establishing themselves and slimes be washed onto surrounding areas or into watercourses. This paper presents the argument that the results of contouring heaps are counter to good environmental practice. Calculations which have been made demonstrate that leveling and berming the heap tops as well as berming the edge of each lift or setback will effectively prevent water erosion and promote the growth of native plant species.

Jan 1, 1993

By C. I. Basilio

Pearson's hard and soft acid and base (HSAB) principle may be applied to flotation systems. The HSAB principle states that hard acids prefer to bond with hard bases and soft acids prefer to bond with soft bases. By determining the Drago E and C parameters for the different components of a flotation system, the HSAB principle could be used to explain the selectivity of some collectors such as thionocarbamates against some minerals. Determination of these parameters is done by utilizing Drago's theory and flow micro-calorimetry.

Jan 1, 1991

By Langtry E. Lynd

The titanium industry is based on the unique properties of titanium dioxide and titanium metal. Because of its whiteness, high refractive index and resulting light scattering ability, titanium dioxide in its two main allotropic forms, rutile and anatase, is the predominant white pigment for paints, paper, plastics, rubber, and various other materials. Titanium metal, because of its high strength/weight ratio and resistance to corrosion, is widely used for aircraft, both in airframes and engines, for powerplant surface condensers, and a wide variety of chemical processing and handling equipment. U.S. production of titanium dioxide pigment in 1979 was about 658,000 tons - 2/, valued at about $770 million. Net shipments of titanium mill products were around 19,000 tons, worth about $380 million. These two major uses account for over 96% of domestic titanium consumption. The third largest application, the use of rutile for coating welding rods, required about 9,500 tons of rutile concentrate, worth about $4 million. Other applications of titanium-bearing raw materials include the manufacture of titanium carbides, ceramics, and chemicals, and the recently developed use of ilmenite as a substitute for barite in well-drilling muds.

Jan 1, 1980

By B. Sameti

Blast engineers have been taking advantage of image-based rock fragmentation analysis methods for the past 3 decades to estimate rock size distributions. These methods utilize a wide range of image segmentation techniques, from manual to fully-automated, to delineate the edges of rocks in images. Rock delineation results are then converted to physical rock sizes (and percentage passing curves) by scaling the image pixels to correspond to physical measurements. The size scaling process is critical for acquiring physical measurements, but specific to the limitations of different applications. This article starts by presenting a shovel bucket-based fragmentation analysis system, where scaling is done using the known width of the shovel bucket within the image. Next, it describes methods that use pictures captured by digital cameras with scaling reference objects in the view. Finally, the article presents a method that uses three-dimensional imaging to capture images without the need for scaling reference objects. A portable device which utilizes a three-dimensional imaging method is proposed, and compared with the other methods. The proposed solution combines the generated three-dimensional points with the delineated rock boundaries in the image to reconstruct the surface, and generate accurate rock size estimates and percentage passing rock size distributions. System operation is described and its accuracy and performance are discussed for various scenarios. It is shown that since the device does not require a physical object for scaling reference, it is free from the limitations of other methods, and can be applied for automatic rock size measurement from various sources such as mining shovels, loaders, crushers, stockpiles, haul truck beds, and conveyor belts.

Feb 23, 2014

By G. J. Karabin

The Boundary Element Method of Numerical Modeling has become an increasingly popular rock mechanics -mine design tool. It has been used by the Roof Control Division, Pittsburgh Safety and Health Technology Center, MSHA, to aid in the resolution of complex ground control problems since 1985. This paper will present an overview of an evolving simulation process and details of methods utilized to generate necessary coal, rock and gob input properties. Also included is a description of a Deterioration Index System that is used to link model output to observed mine conditions and two case studies to illustrate that process.

Jan 1, 1995

By J. A. Rusnak, K. M. Mohamed, M. A. Van Dyke, M. M. Sears, G. Rashed

"Researchers from the National Institute for Occupational Safety and Health (NIOSH) recently developed a coal-mass model to realistically simulate the deformation and loading behaviors of the ribs of coal pillars in underground coal mines. The scale-dependent properties (stiffness and strength) of coal material were considered in the coal-mass model. In this paper the orientation of face cleat with respect to driving direction was integrated in the coal-mass model. The controlling parameters (dimensionless coal-mass scale and fracture strains) of the modified coal-mass model were calibrated using a published case study of coal pillar strength. Numerical models with wide ranges of controlling parameters were conducted to simulate the test pillar. The best match between the numerical modeling results and the measured stresses and deformations was achieved by using a coal-mass scale of 30 and fracture plastic shear and tensile strains of 3.25% and 0.325 %, respectively. INTRODUCTION The failure of coal pillar ribs by itself are a major hazard in underground coal mines. Furthermore, failing ribs can indirectly contribute to roof and floor instability by increasing opening widths across intersections and entryways. Over the past decade, rib failures have resulted in 12 fatalities, representing 28% of the ground-fall fatalities in U.S. underground coal mines. Mining depth has always played a very important role in assessing rib stability. Gauna and Mark (2010) completed an analysis of rib fatalities that occurred between 1996 and 2010. One of their most prominent and influential findings was the identification of a relationship among fatalities, depth, and mining height. Therefore, Coal rib stability will continue to be a challenge for future deeper mines in U.S. coal basins. In the past several decades, research efforts have focused on roof support. The current rib control practice in U.S. coal mines is to select rib bolts through a trial-and-error approach (Mohamed et al., 2015a). Rib failure incidents can be can be substantially reduced or even eliminated by adopting an engineering-based coal rib design approach. The factors affecting rib stability in coal mines are numerous and mutually dependent. These factors include but not limited to mining height and overburden depth, interburden thickness for multiple-seam mining, coal strength, cleat density, entry direction with respect to cleat orientation, existence or absence of partings in the coal, percentage of extracted roof and/or floor rock, density of rib bolt support (Mohamed et al., 2015a). Moreover, it is difficult to isolate the particular effect of a specific factor on the overall rib stability. Therefore, a reliable empirical rib design approach is not achievable because it requires a significant number of case histories to be collected in order to have a reasonable range of all of the critical parameters. However, numerical modeling can be a practical tool to assist with rib support design if the modeling is realistic, which can only be achieved through calibration and validation of the numerical model against field data."

Jan 1, 2018

By Dianne M. Satalic, Peter A. Spencer

Bacterial leaching is a mature technology and has been applied in six commercial plants with others in the design stage or under construction. Bacterial oxidation is a relatively inexpensive process which uses naturally occurring soil bacteria to assist in extraction of base and precious metals. Bacterial oxidation has ini­tially been applied for gold recovery but the technology is now being transferred to base metal leaching with processes already developed for copper, cobalt and nickel. Bacterial oxidation plants often have capital and operating cost advantages over competing technologies and do not need a highly skilled workforce. The most common species found in the conditions used for bacterial oxidation and bacterial leaching are Thiobacillus fer­rooxidans and Thiobacillus thiooxidans. One common species other than Thiobaci!lus found in the commercial bacterial leach cultures is Leptospirillum ferrooxidans. Mixed cultures of the three species named here have formed the basis of the technolo­gy applied in most of the commercial applications of bacterial leaching to date. These bacterial species already mentioned all belong in the classification of mesophiles and have an operating range from 20 to 43°C. One other culture, a moderate thermophile operating over the range 40 to 50°C, has been used in one commercial plant in Western Australia. Bacterial oxidation takes place in acidic solutions under aer­obic conditions. The oxidation reaction normally produces iron (II) in solution which is ultimately conve1ted into the iron (III) form. The pH value falls naturally as the sulphide minerals are oxidised and the starting pH value can fall as low as pH 0.6 as the oxidation reaction proceeds. This paper examines the impact of the technology selection and its application on the design, engineering and operation of a bacterial oxidation plant. The effect of the changes to these para­meters on the cost of the bacterial oxidation plant is discussed.

Jan 1, 1998

By R. W. Amstutz

Abstract. The shaft was drilled on U.S. Government land in the Piceance Creek Basin and was funded by the U.S. Bureau of Mines. It was drilled to 723 meters (2 371') to provide access to rich deposits of oil shale, nahcolite and dawsonite for geotechnical test work and environmental mining research. Rotary drilling and dual string, reverse-air, jet-assist circulation methods were used. Drilling required 8 months. Site preparation, running and cementing the casing required another 4 months. A 2.44-meter (96-inch) ID steel welded casing, 5.1 cm (2 inches) thick was installed and 2 700 tonnes (63 000 sacks) of cement were slurried and pumped into the annulus.

Jan 1, 1980

It has been reported previously that dolomite samples from different locations showed varying flocculation behavior with Poly(ethyleneoxide) (PEO). In this study it is determined that palygorskite associated with the Florida dolomite samples is responsible for their flocculation with PEO. A detailed characterization of the dolomite samples from different locations and its relevance to flocculation with PEO is discussed.

Jan 1, 1994

By R. S. Datta

In the article "Concentration of Oil Shale,"(1) Dr. N. Arbiter stated, "One of the major factors in the delayed utilization of oil shale as an energy raw material is the low grade or content of hydrocarbon (kerogen) in oil shale as compared with coal and even more so to the liquid and gaseous fuels. " When the availability of high-grade deposits decreased, mineral industries started adopting prebeneficiation procedures for the low-grade deposits. This practice, which is becoming standard in these other industries, has been largely overlooked by the oil shale industry in its drive to produce oil from oil shale. If a major portion of this mineral matter can be removed, there can be potentially large savings in the capital and operating costs of oil shale retorts. Moreover, the environmental impact, associated with recovering the shale oil, could be reduced considerably. In 1980 Roberts & Schaefer Resource Service (RSRS) completed successfully the first set of demonstration runs with a 20-ton oil shale sample from Cathedral Bluffs (C-b tract), Colorado. This relatively low grade (~12 gpt oil content) oil shale was beneficiated applying the Dutch State Mines Heavy Medium Cyclone process. (2)

Jan 1, 1985

By G. Southam

Bacterial populations play an active role in mineral weathering in subsurface and near-surface environments e.g., supergene enrichment of Cu at Morenci, AZ. An in vitro bacterial biofilm model was used to examine the interaction between Sporosarcina ureae and ionic gold (which is toxic) or amino acid-gold complexes in gold mobility. The immobilization of ionic gold was between 80-90% for 1 week but as the available, cellular reactive sites became saturated immobilization decreased to 14% within 2 weeks. In the asparagine-gold system, gold immobilization occurred at a high rate (80-90%) throughout the experiment with limited toxicity towards Sporosarcina ureae.

Jan 1, 1999

By M. Sears, W. H. Su, J. Wickline, M. A. Van Dyke, G. Esterhuizen, Z. Khademian

It is commonly recognized that seismicity can be induced by rock failures or slip along geologic structures around mining excavations. The unpredictable nature of these events and their proximity to the working area may raise safety concerns in underground mining operations. Modeling can be a useful tool for estimating seismic potential for a given mine layout, but the challenge is to detect a seismic event and estimate its intensity in the model. One well-documented approach is to monitor the variation in the energy content of the model and record potentially damaging seismic events when there is a significant release of energy. Researchers from the National Institute for Occupational Safety and Health (NIOSH) employed this approach using 3DEC modeling software to simulate the anomalous seismic events that occurred in a deep longwall mine in Virginia in 2005. A four-panel model of the mine was constructed utilizing a 2D cross section at the location of the mining face at the time of the event. Seismic potentials associated with the development of each panel are evaluated by recording the seismic energy released during the simulation. The results demonstrate the occurrence of two relatively significant events during the mining of the last panel, which are consistent with the historical observations at the mine.

Apr 26, 2022

By P. A. Cornejo

Blastings always generates induced vibrations through seismic wave, these are lost energy from the blasting and therefore causing the disturbance of slopes and structures near the blast source. Most of the components of an open pit mine have to reach a physical stability, especially during its closure process. Aiming to develop a vibration prediction model using the historical records from an open pit mine located on Peru, this research has two main focuses depending on the distance from the blast source to the structure: to protect the final slopes and to protect the villagers houses. Both are based on the Devine model of the Square Root Scaled Distance (SRSD) to predict the Peak Particle Velocity (PPV). The Mid field model, where is found mainly final slopes from the pit, limited by the failure criteria of McKenzie based on the geo mechanical properties of the rock mass. The Far field model ranges distances where are located the most community households, limited by the German rule DIN 4150 for highly sensitive structures. Both scenarios resulted on a distribution abacus to limit the weight of used explosives to get the best operational advantage and structure safety.

Mar 2, 2022

By Charles R. Marek

There is an ever-increasing need for quality construction materials to provide the necessary housing and transportation facilities required for the protection and movement of people and goods. By the year 2000, requirements for housing in the United States will have doubled due to population growth. Requirements for transportation facilities in this same period will also have increased substantially. Further, all existing facilities for both housing and transportation will require substantial maintenance of one form or another. Aggregate is the basic material of the construction industry. There is some occurrence of aggregate source material in virtually every state of the United States, and in every country in the world. United States reserves of commercially useable aggregate have never been systematically estimated and are probably so vast as to be incalculable.1 However, in many areas its existence is largely negated by inaccessibility. Often it is lodged deeply or intricately in the earth or it is too distant from markets to offer a desirable "return on investment" under the present economic structure. Other factors that prevent its utility are the occurrence of small scattered deposits that individually are too small to justify the necessary capital investment for exploitation and collectively are too widely disseminated; also, the aggregate nay be deficient in certain desired chemical or physical qualitites.1

Jan 1, 1974

By A. W. Khair

This paper presents a strength formula for the design of coal pillars. The formula is derived from results of laboratory experiments, studying the effects of primary factors influencing the strength of the coal specimens/pillars. Five primary factors, significantly affecting the strength characteristics of the coal specimens/pillars were identified and extensive laboratory investigations were carried out. The five primary factors were namely 1) coefficient of friction between loading platens and coal specimens, 2) elastic properties of the loading platens, 3) coal specimen geometry, 4) coal specimen size, and 5) rate of loading. Four to nine levels of variation for each primary factor on the strength of coal were studied. An empirical formula, implementing the variation of the primary factors affecting the strength of coal specimens/pillars, has been developed. A comparative analysis of the results provided by this and some well known formulae is also presented.

Jan 1, 1994

By T. R. West

Planning for urban development in many locations is based largely on 0.10 factors, 1) soil conditions and 2) socio-political aspects of the region. A more widely based approach is necessary, however, if a complete and functional plan is to be obtained. Under this unified approach, the overall field of earth science is included in the planning process. As considered here, the earth sciences comprise a large segment of the natural sciences; that is, geology, pedology, geomorphology, reengineering geology and ground water hydrology. A number of shortcomings can develop when using the restrictive, two-factor approach for urban development planning. These deficiencies are discussed in the paper. The specific considerations for each earth science area are examined and land use considerations for various urban requirements reviewed in light of these specialties. To illustrate the potential of the unified or earth science approach, Tippecanoe County, Indiana is presented as an example. The current area planning system for Tippecanoe County is examined to determine how well it compares with the unified approach and some of the shortcomings of the current plans are discussed.

Jan 1, 1972

By J. R. Dyni

Colorado nahcolite deposits, estimated at 29 billion metric tons, formed in an asp metric permanent-lake basin whose waters were rich in algae and sulfate-reducing bacteria. Nahcolite (NaHCOg) occurs in oil shale of the Green River Formation (Eocene) as aggregates (62 percent), disseminated crystals (24 percent), and impure beds (14 percent). Because much of the nahcolite is nonbedded, it will be mined with oil shale and can be concentrated to marketable grade by crushing and screening Impurities in nahcolite are kerogen, quartz, pyrite, and carbonate minerals. A promising new market for nahcolite is in the process of removal of sulfur dioxide from industrial stack gases. When heated, nahcolite reacts with sulfur dioxide to form sodium sulfate. Differences in thermally induced microporosity may explain why nahcolite is more reactive than trona, a possible competitor with nahcolite for SO2 removal. Limited production of nahcolite at one or possibly two localities is expected in the next several years, but large-scale production is probably at least 10 years away.

Jan 1, 1980

By A. R. Laplante

A novel methodology to estimate gold recovery by gravity is presented. The methodology makes use of a population balance model which represents gold liberation, breakage and classification behaviour and applies pre-concentration and recovery performance curves to gravity-recoverable gold to predict overall recovery. Derivation of the necessary parameters is explained and demonstrated using data from an actual gravity circuit and one projected application. The methodology makes it possible to estimate the performance of circuits with large gold circulating loads and relatively low unit recoveries (e.g. jigs), or with high recoveries on a bleed of the circulating load (e.g. Knelson concentrators).

Jan 1, 1994

By W. J. Guay

Carbonaceous gold ores containing gold dispersed in sulfides are refractory to cyanidation because: ( 1) the carbonaceous materials adsorb gold during cyanidation; (2) a portion of the gold is so finely dispersed in the sulfide mineral lattice as to preclude contact with cyanide solution; and (3) a portion of the gold is chemically combined with carbonaceous material. Techniques which have been used to treat these ores are: (1) roasting or chemical oxidation to decompose sulfides and carbonaceous materials; (2) flotation to reject carbon; (3) the use of kerosene or other reagents to passivate the adsorptive carbon compounds; (4) carbon or resin in pulp; (5) flotation of a bulk concentrate which is treated by one of the above methods; and (6) the use of chelating agents which have a stronger affinity for gold than the activated carbon in the ore.

Jan 1, 1981