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By W. W. Vaughn

In the technique described and evaluated, detection of mercury is based on the principle of atomic absorption. An analog signal, produced when mercury vapor absorbs ultraviolet light, is converted to digital form and calibrated to mercury concentration. Interferences are eliminated by selectively trapping the mercury on gold. The lower limit of sensitivity, using a 1-gram sample, is 5 parts per billion. A model of the instrument mounted in a station wagon has been tested successfully in the field.

Jan 1, 1964

By Daniel T. Brian, O&apos

Exploration targets and results in the mining industry are commonly summarized in terms of tonnage and grade. Business appraisals require, as additional information, the expected profit or loss implied by the physical summary. The early incorporation of knowledge gained through financial analysis computations can provide a means for economically resolving many common exploration and development problems. Examples of such applications from the activities of exploration planning, reconnaissance, land acquisition, and development planning are presented in this paper.

Jan 1, 1969

By Walter E. Kramer

The advantages derived from the use of pellet burdens in blast furnaces are so great, that hematite ores are being converted into pellets in greater quantities each year. The conversion of these ores into pellets appears on the surface to be relatively simple. In reality, this is not so. Serious difficulties are encountered in drying these pellets that do not exist in the drying of taconite concentrate pellets. The ores that present problems are goethite and earthy hematites. Green pellets prepared from these ores have very law shock temperatures, 200-600° F. The shock temperature of a green pellet according to our definition is the highest initial temperature to which a green pellet may be exposed without suffering decrepitation. Decrepitation may involve spalling, fracturing or total disintegration. The poor shock properties of these green pellets result from the inability of the vaporized water to escape freely and easily as it is formed with¬out affecting the integrity of the pellet. As a consequence, the pellets must be carefully dried prior to induration. This careful treatment is costly. The slow drying process restricts productivity and requires larger furnaces than desired. The use of an additive to elevate the shock temperature of the green pellets would increase productivity. Bentonite is used in some pellet plants to improve balling but it raises the shock temperature only slightly. Nalco became interested in the shock temperature problem because of its activity in the development of organic pelletizing aids for taconite concentrates. The findings reported here are an outgrowth of our experimental work on the development of shock temperature additives.

Jan 1, 1967

By Allen V. Reicks

Modern conveyor pulleys are welded steel structures subjected to dynamic loads. In this paper, fatigue notch and fracture mechanics methods are applied to several weld joints on typical pulley constructions. These methods are used to analyze field applications and are correlated with laboratory testing. Generalized approaches are presented which provide high confidence in pulley design with corresponding high reliability.

Jan 1, 1996

By R. J. Sweigard, R. V. Ramani

Productive and beneficial use of reclaimed surface-mined land is a concern of industry, government, and the general public. A process has been developed that will aid mine planners and public planners in the evaluation of postmining land use potential. This process involves the application of site planning principles to surface-mined land in a way that ensures productive end use of reclaimed land. The process consists of 10 basic components and is iterative in nature. Termination of the process depends on the amount of data collected and the evaluation requirements of each mining site. The analysis centers around the economic, environmental, and social impacts of the alternative land use plans.

Jan 1, 1987

By O. Akinkugbe

The safe, productive exploitation of coal in multiple-seam situations requires specific design technology. At present, there are two general design approaches that the mining engineer can use to analyze the multiple-seam problem in question, either simple empirical relationships or complex numerical models. Often, the empirical approaches are too general for the specific problem and the numerical models require too much time and expertise for the practicing engineer. In this paper, a new program designed for quickly and easily calculating the stresses, strains, and safety factors associated with basic multiple-seam mining situations is presented. The program implements a simplified, two-dimensional boundary-element method in order to model the complex multiple-seam stress and displacement interactions. The program incorporates automatic coal and gob property generation to simplify the input, and inherently calculates pillar safety factors to enhance the output.

Jan 1, 2004

By O. A. Bascur

In recent years, metal-producing companies have increased their investment in automation and technological innovation, embracing new opportunities to enable transformational change. Transformation to a digital plant can fundamentally revolutionize how industrial complexes operate. The abundant and growing quantity of real-time data and events collected in the grinding and flotation circuits in a mineral processing plant can be used to solve operational issues and optimize plant performance. A grade recovery model is used to identify the best operating conditions in real time. A strategy for increasing the value of instrumentation in current plants is reviewed. An optimal Gaudin size distribution model provides augmented information from traditional sensors to find the optimal grind cut size to reduce metal losses in the flotation circuits. Sensors in flotation circuits enable an estimate of the recovery and determination of the optimal froth depth and aeration using an air hold up flotation model. A strategy of classifying data for online generation of insights to using operational intelligence tools is described. The implementation of a recovery/grind strategy with industrial examples in nonferrous mineral processing is presented.

By D. B. Jenkins, D. R. Taylor

Treatment of bentonite clay with mineral acids yields a modified clay product of high surface area and acidity that exhibits enhanced adsorptive and catalytic properties. A highly specialized segment of the clay industry based on this process has evolved into a worldwide business with a capacity of about 500 kt/a. This paper will present data on the chemistry, mining, manufacturing, and applications for acid-activated clays.

Jan 1, 1988

By Fabio Amaya, Andrés Marulanda, Ramiro Gutiérrez, Alberto Marulanda

The behavior of a salt rock mass is strongly related to a creep phenomenon. The amount of creep depends on the level of stress generated in the underground excavation. Additionally, security conditions and the lifespan of an underground cavern excavated under this geological conditions depend on the evolution of creep. Based on the experience of the failure of the Old Underground Salt Cathedral of Zipaquirá(Colombia) and the construction of the new one, the theoretical framework to predict the creep behavior of a salt rock mass is explained. The theoretical formulations are calibrated based on actual observations of the material behavior to predict the lifespan of this striking structure.

Jan 1, 2003

By Bert Allard, Åsa Sjöblom

The River Vormbäcken is the recipient of treated AMD from the Kristineberg mine site, northern Sweden, where mining of a complex sulfidic ore has taken place since 1940. Parts of the river flow through different kinds of wetlands. The changes in metal concentrations and water chemistry that occur upon passing these wetlands have been studied by analysis of water chemistry data from a number of stations along the river collected during 11 years of monthly sampling. It is concluded that the impact and functioning of wetlands cannot be elucidated from chemistry data alone. Future studies including e.g. reconstructed water flow are needed.

Jan 1, 2000

By W. K. O’Connor, J. C. White, P. C. Turner

The US Bureau of Mines is investigating the cobalt and manganese resource of the West-Central Arkansas district through field investigations, mineralogical characterization, beneficiation and hydrometallurgical tests. Located within the Ouachita Mountains, these structurally-controlled deposits occur along the axes of anticlines that form the mountain ridges. Brecciated novaculite is cemented with a mixture of manganese oxides, primarily cryptomelane and psilomelane. Cobalt is concentrated within lithiophorite, a particular Mnoxide phase. Chemical analyses of head samples reported up to 25% Mn and 0.17% Co. Magnetic separation yielded products containing up to 41 % Mn and 0.22% Co at recoveries of 95% and 93%, respectively.

Jan 1, 1993

By Tzou-Shin Ueng

Rock reinforcement of rock anchors and rock bolts are commonly used for the support of large rock caverns. The rocks at the location of most large underground openings are usually under very high initial stresses prior to excavation. Hence, the stress redistribution caused by excavation will induce considerable rebound deformations of rocks surrounding the caverns. Since the pressures exerted by the reinforcement are generally far below the initial rock stresses, the reinforcement will be stretched along with the rock deformations, and the stresses in the reinforcement increase accordingly. It is not uncommon for the stress in the reinforcement to reach the yield strength, and in some cases the reinforcement may even have failed. Therefore, the increase of stresses caused by the rebound deformations of rocks should be taken into account in addition to the force required to stabilize the caverns. It was found that the measured stress increases of the prestressed tendons after installation were in good agreement with those computed based on the measured rock deformations between surface and the anchoring point of the reinforcement. The rebound rock deformations and the stress increases in the reinforcement can be estimated based on the results of the finite element analysis and experiences in previous field measurements incorporated with considerations of the geologic conditions, rock properties, rock reinforcement and construction procedures.

Jan 1, 1986

By Donald Ross-Watt

Mining project investment concerns the installation of mine capacity for the purpose of generating a stream of future economic benefits. In order to make this type of investment decision, the optimum specifications for the project must first be determined. Then, the economic justification of the investment tin be evaluated based on these specifications. Economic evaluation to guide mining project investment decisions is based on a proposed plan for mining the deposit over its operational life. If single point estimates are made of deposit characteristics and environmental parameters* as the basis for assessing a future stream of economic benefits associated with the investment, a future mining-plan can be optimally fitted to these estimates and, to the extent that such estimates are actually realized, this plan will retain optimality.

Jan 1, 1979

By K. Osseo-Asare

Metal recovery from solution, i.e., the formation of a solid product from a purified aqueous electrolyte solution, is increasingly becoming more than a simple matter of bulk precipitation. In many cases, operating conditions must be carefully manipulated to control the rate and yield of the precipitation/crystallization process, as well as the purity and physical characteristics of the solid product. A review is presented of the underlying physico-chemical processes, with emphasis on solution and interfacial chemistry. Opportunities for the integration of hydrometallurgical metal recovery and materials processing operations are discussed.

Jan 1, 1989

By S. K. Kawatra, R. A. Seitz

There is considerable variation in the types of coal flotation circuits in use in various parts of the world. For example, Russian plants frequently use scavenger flotation, while this is almost unheard of in the United States. The numerous circuit designs are intended to address specific problems in coal flotation, or to take advantage of the peculiarities of certain coal deposits. As a result, it can be difficult to decide which circuit is best for a given application. For this paper, coal flotation circuits were collected worldwide from many operating plants. These circuits include varying degrees of conditioning, and complexity ranging from simple rougher flotation to multi-stage split- stream processing. The design goals of each circuit are described, and the advantages and disadvantages of each are discussed. Extensive sampling campaigns were carried out in two plants with the most common types of coal flotation circuit (simple rougher, and rougher with deslimed feed). The performance of each plant was evaluated, and the benefits of more sophisticated processing in each case are described.

Jan 1, 1993

By Lawrence Adler

[An innovative framework is proposed which most efficiently and systematically handles the large quantity of information needed for equipment failure and other non-performance analyses. It is based on the accepted engineering dimensions of mass (material), length (geometry), and time (MLT). To these are added human and machine factor. Several failure "Modes" are identified for each dimension, which are then subdivided into specific "Types". Material Failure Modes such as Separation and Slip are easily recognized, but others had to be established. Geometric Failure Modes are usually straight-forward, Obvious ones include Geometrics Design and Stability with more synthesized. Time Failure Modes are again largely self-evident such as Life and Chemical Effects, others are needed. Human and Machine Factors as failure modes are loosely assembled. The results contain strengths, but also organizational weaknesses which are noted. Lacking a better alternative its use is recommended.]

Jan 1, 1989

By W. M. Husslage, M. E. Kock, T. Bakker, R. H. Heerema

Permeability in the blast furnace shaft is adversely affected by low-temperature reduction degradation of sinters. The fundamental cause of this is the expansion of the iron oxide phase resulting from the reduction of hematite to magnetite. The present study shows that expansion behavior during the hematite/magnetite reduction .step and the resulting microstructure are strongly influenced by the reduction temperature (partial oxygen pressure), the reducing agent and the nature of the hematite. The reduction rate is of minor importance. A reduction mechanism is proposed that can explain the dilation behavior and the magnetite microstructure. The results provide better insight into the reduction degradation behavior.

Jan 1, 2000

By Palmer C. Sweet

By-products from mining and processing plants and coal-fired power plants are being utilized more as valuable resources in Virginia. Mining-related by- products are divided into two categories: those generated from mineral extraction and beneficiation, and those generated from mineral processing or from industrial plants. Materials from both categories are produced in Virginia, where by-products have been exploited for various uses in the past and/or present. These materials include coal- combustion products (fly ash and bottom ash), lime-kiln dust, flue-gas-desulfurization residue, rock fines, magnetite, Cold Spring clay (kaolin), Austinville tailings, soapstone rock, and calcium-carbonate paste. Some of these by-products have never been utilized, although several ideas have been investigated over the years.

Jan 1, 1999

By Alfredo Menendez, Alberto Sarmentero

A B S T R A C T The Los Pijiguaos bauxite is one of the largest accumulations of trihydrate alumina ore recently discovered; it is a plateau type, with no overburden, relatively soft tertiary quartz-bearing bauxite developed on a pre-Cambrian Rapakivi Granite batholith. The deposits are found in the northwestern rim of the Guiana Shield, State of Bolivar, Venezuela, and were discovered in 1976 after a grass-roots exploration campaign. Target areas were mainly selected on the basis of geological and geo¬morpholigcal criteria, guided by correlation with known deposits elsewhere in the Guiana Shield. The vertical. lateritic profile consists of an upper concretionary zone, followed by a mottled zone, a palid zone and finally the weathered rock merging into fresh granite. The upper concretionary zone displays a cellular, pisolitic or spongy texture and contains the following minerals: gibbsite (60-90%),quartz (5-10%), hematite (5-10%), goethite (under 5%), boehmite (traces), kaolinite (traces). The gibbsite content decreases sharply downward from the lower limit of the concretionary zone and the kaolinite and quartz content increases in the underlying mottled zone. The mottled and palid zones display a pseudo rapakivi texture and quartz, kaolinite and mica are the. essential minerals.

Jan 1, 1984

By Jeffery L. Kohler

The research and development of a pattern recognition system which can predict incipient failures and safety hazards in the mine power network is described. An examination of mine electrical safety hazards revealed they are often related to the electrical equipment down-time experienced on mine sections. Based on this, a method is proposed that can improve both production and safety, without compromising either. Equipment failure modes are examined to illustrate how the ultimate failure can be predicted for enough in advance to allow a convenient and safe repair, followed by a discussion of actual monitoring system performance. Finally, the paper is concluded by projections of the system's utility to industry.

Jan 1, 1977