Search Documents

By D. A. Stanley

The Bureau of Mines has developed an equation which describes the dewatering of clay slurries with polyethylene oxide. This dewatering equation is An _ kC + b where n, k. and b are empirical constants and C is the concentration of polymer solution used for dewatering. The minimum amount of polymer required for dewatering. A is determined by titration of the clay slurry with a polymer solution. In this report, the dewatering equation is applied to data obtained for a polyacrylamide dewatering sequence. Fundamental similarities between the dewatering properties of clays and the viscosity of polymer solutions were observed. These similarities were explained by correlating an equation describing polymer configuration in solution with the dewatering equation. This correlation showed that amount of polymer required for dewatering and polymer solution viscosity are both consequences of the frictional interaction of entangled polymer coils.

Jan 1, 1989

By M. Fig, A. Juganda, M. Zurhorst, J. Brune, C. Strebinger, G. Bogin

"Understanding the airflow patterns in and around the longwall panel can help to identify poorly ventilated areas that may be prone to methane accumulation. Ventilation network modeling provides quick simulation time, and flexibility in adjusting airway parameters and ventilation controls. Such modeling is effective for analyzing linear ventilation networks in underground mines, but cannot compute flows in caved areas of hard rock mines or longwall gobs. The use of Computational Fluid Dynamics (CFD) enables a more detailed investigation of the interaction between the airflows in these caved areas but requires much longer computational times, designing complex meshes and determination of a variety of modeling parameters. Airway friction factors and ventilation controls are simple to implement in a network model but can be difficult to model and adjust in CFD. This paper will focus on using mine ventilation network simulation to identify and analyze key parameters that are affecting airflow distribution in and around the longwall panels, prior to more detailed analysis with CFD modeling, using the example of a longwall coal mine. INTRODUCTION In longwall coal mine ventilation systems common in the U.S., the main purpose of bleeder ventilation is to dilute methane gas and prevent the formation of explosive gas mixtures in the caved, poorly ventilated gob areas and adjacent mine workings. In longwall operation, these critical areas include the development headings inby the longwall face, and the gob. Methane-air explosions in these areas may be ignited by spontaneous combustion, rock-on-rock friction and other sources. Although rare, ignitions due to rock-on-rock friction caused by roof falls caving into the longwall gob are possible and were suspected in the Willow Creek mine explosions in 1998 and 2000 (Elkins et al., 2001; McKinney et al., 2001). Rock-on-rock frictional ignitions are difficult to prevent, as they occur in inaccessible areas. Therefore, rendering the gob area inert is essential to prevent the formation of explosive mixtures. Research by Gilmore et al. (2015) and Brune et al. (2015) has shown that gob inertization can be a difficult or impossible when using bleeder systems, since the flow of gases through the gob depends on the gob permeability and the amount of fresh air leaking from the face and the immediate roof caving conditions cannot be controlled by the mine operator. Having the ability to predict the location where explosive gas zones (EGZs) form inside the gob will be helpful for designing the best ventilation setup to minimize explosion and fire risks."

Jan 1, 2018

By Ernesto Maldonado, Zach Agioutantis, Jesus Romero

Reliable prediction of dynamic deformations is important when planning to undermine important structures that cannot tolerate large relative deformations and or large horizontal strains. This paper presents examples of dynamic deformation profiles that include subsidence, horizontal displacements, and horizontal strain for a number of points over a retreating longwall panel in the eastern United States. The prediction points are located at different distances from the excavation rib and therefore present a different response in terms of dynamic movements. The formulation is based on the influence function method as implemented in the Surface Deformation Prediction System (SDPS). Results show that the subsidence development curve may be reliably predicted for surface points in the middle of the panel. However, in cases where points may be affected by the magnitude of the edge effect offset, subsidence predictions may be very conservative, that is, higher than actual movements.

Jul 1, 2023

By Peter L. Siems

Humid tropical environments pose many problems for mineral exploration. The problems result from thick lateritic soils, dense vegetation, seasonally heavy rains, deep chemical weathering, few outcrops and thick saprolites. Although geochemical exploration should be potentially a useful technique in these environments, it appears from the scarcity of reports in the literature that insufficient attention has been paid to developing procedures that are specific to the needs of humid tropical areas. For this reason, the authors believe that this account of a geochemical study in a tropical coastal area on the edge of the Brazilian shield is of general interest and importance for potential geochemical exploration surveys in similar areas within the tropics. The objective of the geochemical study was to develop a practical technique of reconnaissance geochemical prospecting for copper deposits in Brazilian tropical coastal lowland areas. In order to achieve this objective, information concerning the secondary dispersion of copper in these areas was required. Consequently, an orientation survey was designed to provide this information. The present account contains details of the geochemical study and the information about the secondary dispersion of copper that was acquired during the course of the orientation survey. Location and Climate The field area is on the Atlantic coastal lowland of Brazil at latitude 13°S. It lies approximately 10 kilometers south of Maragojipe, a city of 15,000 inhabitants; this city is on the western side of the Bay de Todos os Santos about 45 airline kilo¬meters northwest of Salvador. (See Fig. 1) A good gravel road from Sao Felipe to Sao Roque do Paraguay crosses the southern part of the field area. The climate of the area is hot and moist, and is without prolonged dry periods. The mean annual rainfall is about 1600 mm (63 in.) and the greatest precipitation occurs during the winter months of May and June and the summer months of December

Jan 1, 1972

By Henry Antwi

The decade of the 1990s promises to be one of increasing internationalization for domestic minerals producers as they scramble to enhance relative positions in highly competitive, international minerals markets. This "international mining rush" is fueled by developing countries seeking international investment capital to explore for, develop and exploit sizable mineral endowments in an attempt to support the increasingly popular, but expensive, wave of democracy and selfdetermination sweeping the world. This "fuel" typically takes the form of revised mining codes and, often, lucrative investment incentives. These incentives include favorable tax rates, royalty provisions, relaxation of import/ export constraints, depreciation schedules, profit repatriation and other variables that can positively impact mineral investment decision making. Concomitantly, in their attempts to address real and perceived short- and long-term woes associated with enhancing competitive positions internationally, many domestic explorers and producers are attracted to the prospect of finding high-grade deposits in relatively virgin areas. Combined with the investment incentives provided by foreign governments, these high-grade deposits promise lucrative potential returns from projects having short payback periods. Classic examples of this mutual desire to intensify international mining efforts by domestic producers are illustrated by activity levels in countries like Chile, Bolivia and Venezuela in Latin America and, more recently, in Eastern Europe and select locations in the former Soviet Union. As US corporations scurry to send fact-finding, technical, evaluation and financial teams to these presently popular locations, one area of the world has received little attention - Subsaharan Africa. Specifically, the country of Ghana (formerly the Gold Coast) deserves more attention than it appears to be receiving from North American mining companies.

Jan 1, 1992

By C. Duke

The water treatment industry has historically been involved with reducing or inhibiting the inherant scale forming or fouling tendencies of natural waters associated with large industrial cooling water systems. Fouling is an extremely complex phenomenon. From a fundamental point of view, it may be characterized as a combined momentum, heat, and mass transfer problem. Chemical reaction kinetics is involved, as well as the solubility characteristics of salts in water and corrosion technology. It is a routine practice to over size pumps, piping and heat exchangers to compensate for fouling.

Jan 1, 1983

By Dick Lewis

The Misima deposit is on Misima Island in the Lousaide Archipelago, 240 km east-southeast of the Papua New Guinea mainland, and 600 km east of Port Morseby. Misima is a narrow mountainous island 40 km long and up to 10 km wide. The highest point is 1035 m above sea level. Gold mineralization is restricted to the eastern and less rugged third of the island. The Melanesian population lives in coastal villages. Subsistence agriculture is the main activity, although copra and cocoa are grown in plantations on the eastern and southern coasts. Prior to 1950, mining was important in the economy of the island. Climate is tropical, with little seasonal variation in temperature or rainfall. Tropical cyclones occur about every 10 years (Fig. 1).

Jan 1, 1990

By Purnima A. Shivdasan

The fluorspar deposits at Okorusu, Namibia are closely related to an alkaline igneous ring complex of late Cretaceous age (125±7 Ma). The fluorite ores consist of relatively fine-grained purple replacement fluorite and subsequent coarser grained purple and green vug-filling fluorite crystals. Homogenization temperature measurements for 38 primary fluid inclusions shows that main stage purple to green fluorite crystals were deposited over a temperature range from 166°C to 144°C, and minor late yellow fluorite was deposited at lower temperatures from 132°C to 128'C. Homogenization and freezing temperatures measured for 18 primary fluid inclusions shows that the fluorite-depositing fluids were less saline than MVT ore fluids and overlap the lower temperature range of fluids that deposited epithermal ore deposits. Mining in two open pits (A and B) at Okorusu has gradually provided exposures which reveal that the fluorite orebodies have been emplaced primarily by the preferential replacement of carbonatites. Evidence for the replacement of carbonatite includes: 1) replacement remnants of carbonatite within the fluorite ores, 2) goethite pseudomorphs after the carbonatite minerals, pyroxene, pyrrhotite, and magnetite that are disseminated in the fluorite ores, 3) partial replacement by fluorite of a titaniferous magnetite rimmed carbonatite dike in the A pit, and 4) partial replacement by fluorite of a large sill-like carbonatite body in the B pit. Electron microprobe analyses of minerals in unreplaced portions of the carbonatites show that their mineralogy consists of titaniferous magnetite, diopside pyroxene, apatite, biotite, and calcite. Magnetite contains 6.97% to 10.46% Ti02, averages 8.44% Ti02, and has an average V203 content of 0.35%. At high magnifications under the SEM, the magnetite shows abundant fine ulvöspinel exsolution lamellae arranged in a cloth texture. Apatite contains moderately high fluorine contents that range 3.21 to 5.0% and average 4.2%, and apatite crystals range in total rare earth oxides from 1.7% to 2.61%. Pyroxenes in the carbonatites are iron-rich diopside, and they contrast to pyroxenes in the fenites that are aegirine-augite. All of the microprobe analyses for mica crystals in the carbonatites give biotite compositions. The fluorite ores also have replaced marble locally in the A pit, especially along the A band in the B pit, and dominantly in the orebody proposed for the new C pit. Carbonatite and marble were preferentially replaced by fluorite because the calcite was readily soluble in the presence of the fluorite-depositing fluids and the dissolution of calcite provided calcium for the formation of fluorite.

Jan 1, 2005

By C. A. Rowland

Comminution efficiency can be expressed in three different ways. Theoretical Efficiency: actual energy consumed, in a comminution machine compared to the theoretical energy required to make the size reduction. Operating Efficiency: compares the operating work index, calculated from production comminution machinery operating data, to the Bond Work Index from bench scale comminution tests or calculated from pilot plant operating data. Economic Efficiency: income compared to planned income. Using the Bond Work Index and operating work index, this paper explains how to determine operating efficiency.

Jan 1, 1998

By Williams R. Reynolds

Studies of the northeastern Mississippi bauxites were initiated primarily for the purpose of ascertaining the quality and quantity of the ore. Subsequently, this ore was found to have a rather dubious economic value as was previously suspected but never established in earlier economic reports (1, 2, 3). However, the quality of ore was found to be higher than previously thought. Even though the ore bodies were determined during the early stages of this study to be too thin, small and widespread for commercial production a continuation of the study was not abandoned. On the contrary, the present investigation was intensified concentrating less on the economic application and more on stratigraphy and genesis. Considering the ever increasing demand for aluminum products the northeastern Mississippi bauxite district which includes portions of Tippah, Benton, Pontotoc, and Union Counties may soon become, in spite of inferior quantities of ore, an attractive area for bauxite production. Presently, however, the meager quantity of ore discourages exploitation. On the other hand, these northeastern district bauxites are facies of more extensive units of lignite bearing high aluminum clays, and considering the advances in aluminum extraction from clay these clays may in the future beckon mining interest. The bauxite of the northeastern Mississippi district, mapped as a part of the Betheden Formation (4). has an outcrop trend along the county lines of Tippah and Benton Counties and the extreme western portion of Union and Pontotoc Counties. Studies of exposures and cores stratigraphically positions the outcrop between the middle Midway Porters Creek Clay and the lower Eocene Wilcox sands and

Jan 1, 1977

By Carl F. Austin

The subject of strata control in mining can be approached from both static or loading concepts or from dynamic or impulsive loading concepts. The fracture process itself appears to be primarily a dynamic process as is the gross creation of fractures through the use of impact, stress wave passage or in more general terms, the use of explosives. This paper presents experimental results which indicate that the understanding of the fracture behavior of rock that has been, established in the open literature is not always appropriate. In particular, the results of this experimental program have shown very interesting differences between the formation of fractures in rock and the formation of fractures in other materials such as metals and plastics which are often used as models for rock behavior studies Fracture patterns and causes of dynamic fracturing in various rock and artificial materials are presented.

Jan 1, 1965

By Norman Haber

The Haber Gold Process (HGP) is a proprietary. hydrometallurgical extraction methodology that was developed in 1983-1984 by Norman Haber and Dr. John Lee of Haber, Inc., a small public company in Towaco, New Jersey specializing in hydrochemical process development for precious metals. It was pilot tested repeatedly in 1985 at our pilot plant in Tombstone, Arizona, with different types of gold bearing mineralization. Both Pincock, Allen and Holt (USA), and PA Technology (Australia) were involved with some of these pilot tests. The ores tested included easily cyanide-extractable oxide type gold ore from Australia, marginal heap-leach type ore from Cripple Creek, USA, and a hematite bearing ore from California. In all cases, extraction time was 6 hours or less yielding 90-99% recoveries of assayed gold values. The HGP operates as a lixivient which parts the gold from the rock matrix, yielding gold in solution in a fully recoverable form. Both precipitation methods, such as zinc participation or Carbon in Leach systems ( or Carbon in Pulp) have been shown to be feasible with this technology for the recovery of gold from the pregnant solution. Both batch vat leaching as well as continuous processing are realistic for use with the HGP. It has also been considered that the HGP might also benefit heap leaching due to several advantageous factors over cyanide. One such consideration is that the HGP can operate effectively with acidic ore types. The use of cyanide with such ores often requires attention to pH and neutralization with lime. This tends to reduce and even clog the permeability of the leach bed.

Jan 1, 1998

By Colin Connors

Cemented rockfill is a key component in the success of underground mining at the Jerritt Canyon Joint Venture. The Murray and SSX mines are characterized by relatively poor rock mass quality, and the goal of complete mining recovery makes maintaining a high quality backfill product vital to the safety and efficiency of the mining operations. A large portion of the ore production from the Murray mine originates from drifting under backfill. Modelling studies performed to investigate induced loading of the backfill were used to develop engineering specifications for the backfill material. Operations history has shown an almost 100 percent stability of the backfill when mining is carried out beneath it. The volume of backfill required each year (approximately 300,000 tons) and the required cement content have a significant impact on the total mining costs. The potential for cost savings associated with higher replacement of cement with Type "C" fly ash and the implementation of a backfill strength management strategy were therefore evaluated.

Jan 1, 2001

By S. S. Klima, A. L. Mazzella, J. S. Driscoll, T. W. Beck

Previous testing was performed by researchers at the National Institute for Occupational Safety and Health (NIOSH) to improve longwall dust control using underside shield sprays with a longwall directional spray system. This testing provided encouraging results toward respirable dust exposure reductions for longwall personnel, achieving as high as 99% dust reduction at some sampling locations along the longwall personnel walkway. Additional laboratory testing was conducted to test these underside shield sprays in conjunction with a shearer-clearer spray system located on the longwall shearer body. The purpose of this testing was to determine if the underside shield sprays interacted positively or negatively with the shearerclearer sprays. Results from this testing indicate that while the shearerclearer system influences where the respirable dust particles are directed, underside shield sprays can still lower respirable dust exposure for longwall personnel.

Mar 2, 2022

By M. Misra

The coral contaminated with plutonium at Johnston Atoll UA) was subjected to gravity and flotation separation processes at the Soil Washing Laboratory (SWL) and also at the Johnston Atoll UA) site. Tests were conducted with the contaminated coral fractions referred to as the "HP-l" ( hot particles) and the "sludge". The gravity process tested was centrifugal gravity separation and the flotation processes were conventional Denver mechanical flotation and tall column flotation. Flotation tests were conducted using both fresh and sea water. Industrial fatty acid (anionic collector) was chosen as collector to make plutonium-enriched particles hydrophobic. The use of flurosilicic acid and sodium silicate made the clean coral hydrophilic. The results show that each of the processed when tested with appropriate size fraction and operating conditions resulted in passing the success criteria. It was possible to obtain more than 80% weight of the original coral as "clean sand" having activity below the JA site "soil screening level" of 13.5 pCi/gm. The field tests spiked with plutonium particles showed remarkable success. The effect of depressants, flotation medium and the coral pretreatmentis described. Finally, a flowsheet developed by the University of Nevada, Reno to treat 8000 tons of HP-l pile presently stored at JA is presented.

Jan 1, 1996

By W. E. L. Minter

Discussion by E.S. Cheney Minter (1990) has provided an excellent summary of the sedimentology and theories of origin of the Witwatersrand paleoplacer Au/U deposits. However, recent stratigraphic, metamorphic and structural -tectonic research is radically changing the concepts about the Witwatersrand that now occur in most textbooks, review articles and North American minds. Presently, these concepts are biased by the past sedimentological research so well described by Minter. Specifically, the Witwatersrand Supergroup is Archean, does not occupy a depositional basin and is significantly metamorphosed and deformed. Thus, many of its sedimentary features, including the mineralogy of its ores, have been modified. The importance of the Witwatersrand ores cannot be overestimated. Since their discovery in 1886, they have produced 52% of the gold mined in all of human history (Pretorius, 1989). Setting Only one depositional item needs to be added to the excellent

Jan 1, 1992

By Robert C. Edmiston

"Further, we search for the veins by observing the hoar-frosts, which whiten all herbage except that growing over the veins, because the veins emit a warm dry exhalation which hinders the freezing of the moisture, for which reasons such plants appear rather wet than whitened by the frost," Georgius Agricola, De Re Metallica, 1556 In view of Agricola's statement, made in 1556, the concept of using the heat released by oxidizing sulfides as an ore guide can hardly be considered a product of twentieth-century technology. In fact, thermal exploration has received relatively little attention in modern times compared to other potential field geophysical methods. There have evolved, however, two basic approaches to thermal exploration for subsurface heat sources. These are 1) the measurement of surface temperatures by infrared, thermal imagery and 2) the measurement of geothermal gradients in exploratory drill holes.

Jan 1, 1974

By R. Bhaskar

The advantages of recirculation of air in underground mines have been well recognized, and several papers have been written on the subject. Issues of concern to the various segments of the mining industry relate to the health and safety of workers, specifically, methane and respirable dust build-up in the air, high humidity and temperature at the work face. This paper presents a survey of various studies pertaining to recirculation as a prelude to the experimental and quantitative studies performed by the authors. Experiments were performed at a trona mine on the transportation and deposition of dust along the return airways, for three different velocities. Modeling studies were performed using dust deposition models. The model predicted data were compared with experimental data in order to lay the foundation for the development of advanced predictor models for recirculation in trona mines. Two models for dust deposition were analyzed. The model predicted data are in divergence from the experimental data, indicating the need to develop better models.

Jan 1, 1992

By T. B. Szwilski, R. D. Begley

Status of ISO 14000 standards. The ISO 14000 are voluntary international standards providing a frame-work that allows a company to integrate an effective environmental-management system (EMS) into its operations. The purpose of an EMS is to provide a systematic procedure to identify the environmental aspects of a company's activities, evaluate any significant impacts and use the information to set objectives and targets toward continuous improvement of the company's environmental compliance and performance. In addition to the specifications for certification, ISO 14000 can be used as a guide to develop an effective environmental-management system or for self-declaration. The International Organization for Standardization (ISO) is a worldwide federation founded in 1947 to promote the development of international manufacturing, trade and communication standards. The organization is now represented in 118 countries, with the American National Standards Institute (ANSI) representing the United States. The principal goals of the ISO is "to promote the development of standardization and related ac¬tivities in the world with a view toward facilitating the international exchange of goods and services and to develop cooperation in the sphere of intellectual, scientific, technological and economic activity." ISO develops standards with input from government and industry. Because the standards are voluntary, there are no legal requirements to pressure countries to adopt them. However, many governments, industries and US agencies are adopting the ISO standards as a requirement for business trans¬actions, thereby, compelling suppliers to adopt ISO standards. These business and market forces, which are likely to be strategic business issues in the 21st century global marketplace, are imposing the need to develop a systematic approach to environmental management. The ISO 14000 series evolved from a United Nations Conference on the Human Environment in 1972. It includes a broad range of elements: the basic environmental management system, environmental auditing criteria for internal and external auditors, criteria for environmental performance evaluation (EPE), environmental labeling criteria and life-cycle assessment methodologies. The standards comprise two categories: organization evaluation standards and product oriented standards (Table 1). The ISO 14001 specifications contain the requirements for developing an environmental-management system that may be objectively audited for certification. The ISO 14004 standard provides guidance on interpreting the ISO 14000 specifications for the development and implementation of the EMS and for coordination with the management system of the company. On Sept. 1, 1996, the American National Standards Institute (ANSI) and the Registrar Accreditation Board (RAB) signed a formal agreement to create a new entity called the National Accreditation Program (NAP). To obtain certification, a company must fulfill the requirements outlined in ISO 14001. It is required that "a third party give written assurance that a company's EMS meets all the requirements of ISO 14001." Preparing for ISO 14000 can include subscribing to voluntary environmental initiatives; learning from ISO 9000 quality-management experiences; and utilizing information from recognized training courses, publications and numerous Internet resources. Once committed to an EMS, the management should provide sufficient resources to achieve continuous environmental-performance improvement, as outlined in an environmental policy. A thorny issue now being debated concerns the potential liabilities of documenting the environmental performance of a company. General impact of the ISO 14000 EMS standards. With increasing stakeholder awareness, costly end-of-pipe pollution-control approaches and the success of ISO 9000 quality-management standards, the ISO 14000 EMS standards are being adopted by companies and governments worldwide. The United States and Canada have well-established programs. In Europe, countries differ but are firmly committed toward environmental-management standards (BS 7750, EMAS and ISO 14000). The Department of Environmental Protec¬tion of the State of Pennsylvania is using ISO 14000 as a vehicle to develop a closer working relationship with industry, and it is anticipated that this policy will eventually lead to fewer environmental site inspections for those companies with ISO 14001 certification. The Depart-

Jan 1, 1999

By D. L. Stevens

Following an in-depth scenario and strategic planning exercise in 1997, Noranda's mine production goal was set at 500,000 tonnes per year of both copper and zinc metal within five years. There had been no recent discoveries, reserves were shrinking and things had to be done differently and quickly. Change is now continual in our program but here is what we did first: Combined the exploration and business development groups Formed teams to search for and respond to opportunity Made our geologists more business minded and our engineers more optimistic Went global Set clear thresholds, farmed out the marginal properties, fast tracked the others Focused reconnaissance exploration where we had a clear competitive advantage Became a "flexible" partner to both juniors and seniors Is it working? A number of successes, near successes, and outright failures are discussed. The main result is a much higher rate of opportunity flux which is essential for success in the mining industry.

Jan 1, 1999