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By Dorothy A. Canter

Three Federal programs exist for identifying significant environmental chemicals, including minerals, that should be tested for toxicological effects. Two programs are mandated by law and can lead to industry-funded studies; they are administered by the Environmental Protection Agency and the Agency for Toxic Substances and Disease Registry, respectively. The third is the National Toxicology Program, a Federally-funded testing initiative. This paper summarizes the three programs, describes their similarities and differences, and discusses their applicability to minerals.

Jan 1, 1991

By P. B. Altringer

The Bureau of Mines, U.S. Department of the Interior, is investigating biodegradation of cyanide as a means of decommissioning heap leach operations. Biological oxidation decreased weak acid dissociable (WAD) cyanide in process solutions1from 50 to 170 ppm down to 0.1 ppm. The tests were conducted both in trickling column reactors, using quartz as the growth surface, and in upflow columns, using activated carbon as the growth surface. In addition, exploratory tests indicated that bacteria will destroy residual cyanide in leached ore. A flowsheet has been proposed for closure of heap leach operations in which the metals processing portion of the plant, possibly the carbon adsorption columns, or a collection pond is used as a bioreactor. The cyanide in the process solution is destroyed in the bioreactor and the treated water is used to rinse residual cyanide from the spent heaps. The water is recycled until the effluent WAD cyanide concentration meets discharge standards.

Jan 1, 1992

By K. Morsy, S. S. Peng

This paper deals with the causes and mechanisms of a massive pillar failure in a room-and-pillar mine. The mine employed a nine-entry panel system using supersection technique under a cover ranging from 91 to 168 m (300 to 550 ft). Chain pillar squeeze and large roof-to-floor convergence were first observed at the belt transfer point on the very inby side of the main entries. It propagated out by quickly, and, within 24 hours, it had covered an area approximately 1,250-m- (4,100 ft-) long by 762-m- (2,500-ft-) wide. The failure was caught and stopped by a solid barrier pillar. Using computer modeling, this study indicates that the massive failure was initiated because of a combination of undersized chain pillars in some panels and weak immediate floor. Also, the study shows that the massive pillar failure expanded to a large area because of the absence of barrier pillars between some panels and between mains and panels. Based on computer modeling, alternative mine plans were proposed to avoid such problems.

Jan 1, 2002

By S. Mathur

Oxide particles are commonly used as fillers in plastics, paper, rubber, etc. (particulate composites). The successful fabrication of such composites is dependent upon the adhesive strength of the filler particles to the matrix. The compatibility of the matrix and the filler particles is generally enhanced by the adsorption of surface modifiers such as surfactants and polymers at the particle-matrix interface. To develop a scientific basis for the selection of the appropriate modifiers it is necessary to understand their adsorption mechanisms. specifically, the adsorption of polymeric additives is attributed to a combination of chemical and electrostatic interactions, hydrogen bonding and van der Waals forces. Hydrogen bonding has been suggested to be the primary adsorption mechanism for nonionic polymers. However, a literature survey of the Poly(ethylene oxide) (PEO)-oxide system suggested that PEO, a nonionic polymer, was substrate specific. A systematic study was undertaken to investigate the adsorption mechanisms of PEO on oxide particles. It was determined that strong Bronsted acid sites on the surface interact with the ether oxygen, a Lewis base, of PEO to induce adsorption. In this work, characterization of PEO binding sites on oxides is reported and the mechanisms of PEO adsorption are discussed.

Jan 1, 1999

By Tom F. Deems

The term ball clay is applied to plastic sedimentary clays that have a high content of kaolinite and that possess white firing properties and high green strength (Mitchell and Stentiford, 1973). However, the name ball clay is not derived from any specific property of the clay. Instead, it comes from the original method of production in southwestern England (Scott, 1929). From open pits, the clay was cut into cubes with hand tools. The sides of the cubes were about 220 to 250 mm (9 to 10 in.) and weighed 14 to 16 kg (30 to 35 lb.). The eventual rounding of the corners with handling before sale gave rise to the term ball clay. Ball clays provide the workability and green strength required by the whiteware section of the world's ceramic industry. The main applications are in the sanitaryware, tile and tableware sectors. Each, though, requires particular technical properties in the ball clay component. The clay has to be as white firing as possible for all applications. However, for sanitary-ware, the rheological properties are most important. For tableware, fired whiteness and freedom from specking are the main criteria. Tiles need a reasonable green strength but the clay also needs to be cost-effective. The technical properties of the individual clays in any deposit depend on the clay mineral assemblage. This, in turn, depends on the geological formation of the deposits. Hence, it is the latter that largely determines the market sector for which the clay blends from a particular deposit are suited. Formation of ball clays Ball clays are formed from three main components - kaolinite, micaceous minerals and quartz - while carbonaceous material is also often present. The crystallinity of the kaolinite and mica varies. There are also occasional minor occurrences of feldspar, chlorite, montmorillonite andmixed. layer minerals. Marcasite, siderite and anatase also occur in small amounts. The properties of the clay depend on its mineralogical composition and its particle size distribution, particularly in the lowest size ranges. The original source rocks and the environment of deposition of the clay are the controlling factors. The importance of weathering processes in the formation of ball clays has long been recognized (Bristow, 1968). The diversity of source rocks produces considerable variation in the clay minerals formed. Therefore, each deposit is unique, with time-related variation within it. The greatest development of a weathering mantle takes place in a tropical climatic environment. Plant remains confirm that most ball clay deposits were formed under hot and wet conditions. Sedimentation of the clays had to be in fresh or low salinity water or clay minerals detrimental to whiteware manufacture would have been formed. Fresh water traps for the ball clay, sand and lignite sequences depended -on tectonic features, such as basin development along fault zones or lakes and lagoons on the edge of a large scale embayment. These factors for Devon ball clays were discussed by Vincent (1983). The combination of suitable source rocks, tropical climate, significant fresh water sedimentary environment

Jan 1, 1997

By B. C. Flintoff

In general, process control systems in solid-solid separation have not evolved to the same level as in flotation circuit control. Perhaps one of the more significant contributing factors in this regard is the lack of suitable on-line analytical instrumentation. In spite of the obstacles, some interesting work has been done. This paper presents a review of current industrial control strategies in ore sorting, dense media separation, gravity separation and electrical and magnetic separation.

Jan 1, 1986

By Osvaldo A. Bascur

The implementation of continuous quality improvement is the confluence of Total Quality Management, People Empowerment, Performance Indicators and Information Engineering. The supporting information technologies allow a mineral processor to narrow the gap between management business objectives and the process control level. One of the most important contributors is the user friendliness and flexibility of the personal computer in a client/server environment. This synergistic combination when used for real time performance monitoring translates into production cost savings, improved communications and enhanced decision support. Other savings come from reduced time to collect data and perform tedious calculations, act quickly with fresh new data, generate and validate data to be used by others. This paper presents an integrated view of plant management. The selection of the proper tools for continuous quality improvement are described. The process of selecting critical performance monitoring indices for improved plant performance are discussed. The importance of a well balanced technological improvement, personnel empowerment, total quality management and organizational assets are stressed.

Jan 1, 1995

By Laurence M. Demers, Douglas C. Kuhn

It has been suggested that radicals on the surface of dust particles are key chemical factors in the pathophysiology which results from the occupational inhalation of coal and silica dust. In addition, oxygenated derivatives of arachidonic acid (eicosanoids) have been implicated as important biochemical mediators of mineral dust-induced lung disease through their role in bronchial and vascular smooth muscle reactivity, inflammation, and fibrosis. Therefore, we assessed eicosanoid production by the rat alveolar macrophage (AM) exposed in vitro to mineral dusts with varying surface chemical characteristics in order to determine if radicals associated with the mineral dub1 could influence the production of pro-inflammatory mediators in the lung environment. Rat AM were exposed to freshly fractured or "stale" bituminous coal dust, as well as untreated silica or silica calcined to 500°C and 1100°C. Prostaglandin E2 (PGE2) and thromboxane B2 (TxB2) levels in incubation medium were determined by specific radioimmunoassay. When AM were exposed to freshly fractured coal dust, PGE2 and TxB2 production were markedly increased. In contrast, exposure of AM to "stale" dust significantly reduced PGE2 and TxB2 production. In vitro exposure of AM to untreated silica resulted in a significant increase in PGE2 and TxB2 production compared to control. However, exposure of AM to silica calcined to 1100°C resulted in eicosanoid levels which were not significantly different from control. These findings suggest that radicals associated with respirable coal and silica particles may play a key role in the ability of mineral dust to activate AM eicosanoid production.

Jan 1, 1991

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 A. Choudhury

Deep open-pit mines are becoming increasingly common in the highly mineralized arctic and sub-arctic regions. Air inversion is a frequent occurrence in these regions, and is exacerbated by complex geometry of the open pit and the surrounding natural topography of an open-pit mine. The resulting inversion cap is known to contribute to the degradation of air quality in the open pit, resulting in loss of production. This paper discusses the development and validation of a three-dimensional model that simulate the flow of air and the transport of gaseous contaminants in an arctic open-pit mine and the analyzes effect of the geometry of the mine and the slope angle of the pit on the contaminants profiles in the mine.

Feb 27, 2013

By N. I. Aziz, B. Srinivasa Rao, R. N. Singh

The control of respirable dust and its subsequent exposure to miners is essential for improved safety in longwall mining. The extensive variation in face conditions and operations of longwall make numerical modelling an attractive approach in both the development and evaluation of dust control devices. Three dimensional finite element computational fluid dynamics code FIDAP was used to model air velocities and the effect of dust control techniques on dust concentrations at a typical longwall face. The effect of shearer body on airflow characteristics in a longwall face was analysed with both antitropal and homotropal ventilation systems. Path traces of particles introduced near the shearer drums was also simulated. Initial modelling results were validated using field trial results at three operating longwall faces. Results of simulations tallied very well with the field results.

Jan 1, 1993

By Louis G. Silano, Aram Grigoryan

Parsons Brinckerhoff is providing engineering services for the Atlantic Avenue Station Complex Rehabilitation and Passageway Reconstruction for New York City Transit. Project reflects current realities and challenges of underground excavation, support, and construction under operating subway tracks and platforms, and under major transportation hub, comprising three subway stations, railroad terminal station, and busy street intersection. The construction requires extensive underpinning of subway structures and operating tracks. This Paper addresses engineering challenges of IRT subway station rehabilitation and passageway reconstruction without interruption of transit operations and street traffic. Total construction cost of the Project is $ 105,000,000.

Jan 1, 2003

By Leslie E. Apodaca

INTRODTUCTION The use of spiral concentrators for processing fine coal particles is an old idea that has recently gained acceptance in the 11.S. coal industry. It was not onti1 the Australian Minerals Industry developed a spiral concentrator specifically for separating coal from ash in the latter 1970's and early 1980's that spiral concentrators were seriously considered as viable equipment for processing fine coal. The Wright Coal Spiral was introduced in 1980, the Mineral Deposits Limited Mark 10 Coal Spiral was introduced in 1982, and the Vickers Wyong Coal Spiral was introduced in the latter part of 1984. Each spiral design was different and utilized constant profile troughs, constant pitch troughs, compound profile troughs, and various splitter arrangements. Mineral Deposits Limited has combined the best features of the compound profile trough and constant pitch trough with critically-placed splitters to develop the MDL LD4 spiral concentrator which is a truly efficient coal washing spiral. This spiral concentrator was introduced into the U.S. Coal Industry in 1987. Recently, Mineral Engineering Technology of the United Kingdom and Multotec of South Africa have introduced their own coal spiral designs. Spiral concentrators were first installed in fine coal processing circuits in the Australian, South African, and Canadian Coal Industries in the early 1980's and in the U.S. Coal Industry in 1985. SPIRAL CONCENTRATOR SEPARATION PROCESS The separation process that occurs within the spiral concentrator trough is very complex, as it is a combination of three gravity separation processes. When the coal slurry first enters the spiral trough, each coal and ash particle and the water is subjected to centrifugal forces. These forces cause the water, light coal particles, fine heavy ash particles, and medium middlings particles to the outer vertical portion of the spiral trough. The coarse ash particles and the coarse middling particles remain on the inside of the spiral trough. The center or transitional area of the trough contains a mixture of middlings particles and near-gravity material that is present in the slurry, as shown in Figure 1. At the same time the coal and ash particles are suhjected to centrifugal forces, the trough design (both profile and pitch) causes the particles to be subjected to flowing film and stratified bed separations. The combination of these three separations, whose efficiency is dictated by the spiral troogh design, will effect the separation of the lighter coal particles from the heavier ash and middlings particles. As the slurry flows down the spiral, the profile and pitch design of the trough will counteract the centrifugal forces on the fine, heavy ash particles and fine middlings particles and cause them to migrate from the vertical portion of the trough to the center or inner portion of the trough. At the same time, any heavy particles trapped in the transitional area of the trough will be forced to migrate to the inner edge of the trough and any coal particles will be forced to migrate to the outer edge of the trough. SPIRAL SPLI'TTEP ARRANGEMENT The critical placement of splitters along the inner edge of the trough for removal of the heavy ash particles as the slurry flows down the trough further enhances the separation of the coal particles. At the bottom of the spiral trough are product splitters arranged to make a final separation of the slurry stream into clean coal, middlings, and refuse products.

Jan 1, 1988

By Rodrigo Jerez

The mining business in general, and coal mining in particular, is exposed to frequent and significant swings in the business cycle. Marginal coal production enters the market place in a nearly perfect competition. It must be priced aggressively if market share is to be gained. The minimum price acceptable from the standpoint of the producer is reached at the point where total variable cost are recovered. Competition occurs as companies move to reduce their variable costs in an effort to cover some portion of their fixed costs at reduced market prices. Production planning and scheduling plays a critical role in reducing costs. Multiple scenarios based on changing market conditions require that competing firms have tools available to evaluate the economic impact of transportation, blending, and processing options. In certain applications, significant cost savings can occur as a result of blending or altering preparation levels. Linear programming provides a tool with which to evaluate options and acts as a like between the mine plan and marketing decisions.

Jan 1, 1992

By Evan Dressel, Mark S. Diederichs, Kathy Kalenchuk

As hard rock mining develops deeper over time, there is an increasing need to predict the spatial and temporal distribution of adverse seismogenic rockmass reaction to mining. Real-time monitoring and feedback of mine data are used to tactically manage risk associated with induced-seismicity; however, strategic risk management requires reliable tools for forward predictions of seismic hazard. The forward prediction of seismic hazard is strengthened by understanding of potential seismic intensity, which often relies on well calibrated mine-wide numerical models. This paper uses a case study to explore how future seismogenic potential and the nature of future seismicity can be domained according to numerically predicted stress-strain paths at past seismic event locations. Delineation of high confinement seismogenic volumes vs. lower-confinement, high-strain seismogenic volumes at the mine-scale can be achieved, based on a loading and unloading stress path analogue, to refine understanding of seismic intensity. Practical qualitative and quantitative methods to achieve this delineation will be demonstrated. Once seismogenic mode (high-stress vs. high-strain) is identified, detailed analyses of seismic source parameters demonstrates change in seismic hazard between the domained volumes.

Apr 26, 2022

By L. R. Shotwell, C. F. Voss, R. J. Bastian

Pacific Northwest Laboratory (PNL) currently supports the U.S. Department of Energy's Office of Civilian Radioactive Waste Management in developing and evaluating analytical methods for assessing the suitability of sites for geologic disposal of high-level radioactive waste. The research includes consideration of hydrological, geomechanical , geochemical , and waste package components and the evaluation of the degree of coupling that can occur between two or more of these components. The PNL effort and those of other research groups investing potential waste sites in the U.S. and abroad are producing a suite of computer codes to analyze the long-term performace of the proposed repository sites. This paper summarizes the ongoing research in rock mechanics at PNL involving flow through jointed rock. The objective of this research is to develop a methodology for modeling the coupled mechanical-hydrological process of flow through joints and then attempt to validate a "simple" model using small -scale laboratory test data as a basis for judging whether the approach has merit. This paper discusses the laboratory tests being conducted to develop s joint behavioral constitutive model for the numerical method under development and the modeling approach being considered.

Jan 1, 1986

By R. Lai

This paper describes the application of a cyclonic flotation column (CFC) for coal cleaning. A CFC makes use of centrifugal force to create a density gradient in a column to augment the froth flotation process. In a CFC, a series of angular helical inserts is attached to the wall of a conventional column, and coal slurry is mixed with a series of impellers attached to a central shaft. The hydrophobic froth concentrates near the center shaft and moves upward, while the relatively heavy hydrophilic particles concentrate near the wall and are guided downward by the helical inserts. The results of pyritic sulfur removal from an Upper Freeport coal during CFC flotation are discussed.

Jan 1, 2003

By D. C. Shumway

Mining in Cushenbury Canyon began in 1860 when John Cushenbury left his Holcomb Valley gold prospect and discovered a silver vein in the limestones of the present day Cushenbury Mine. Cushenbury Canyon is located along the western boundary of the Mojave Desert in Southern California and on the north slope of the San Bernardino Mountains. The Holcomb Valley, immediately southeast of Cushenbury Canyon was the most prolific gold producer in Southern California. Gold mining dominated the area until World War II when interest in the Lucerne Valley Limestone deposits was peaked by the construction of the Kaiser Steel Plant in Fontana, California. The steel making process required large amounts of metallurgical grade limestone and Kaiser geologists located claims in most of the limestone deposits. Kaiser Cement constructed a cement plant and limestone mine in Cushenbury Canyon in 1956. Kaiser Cement modernized the facility in 1982 to a four stage preheater-precalciner system. Mitsubishi Cement Corp. purchased the property in April, 1988, and through further system modifications have created the most efficient and modern cement plant in the United States.

Jan 1, 1992

By Johann Engelbrecht, Stéfan de Bruyn, Petrus van den Heever

A system for the on-stream X-ray diffractometric determination of mineral phases in slurries was developed in response to the mining industry's need for process control during the beneficiation of industrial minerals. The instrumentation for and results from testwork conducted at a phosphate rock beneficiation plant in Florida are discussed. Results show that the concentrations of the minerals apatite (var. francolite) and quartz can be accurately determined every few minutes, so that adjustments to the flotation circuit can be timeously executed from the control room. The on-stream measurements can ultimately be integrated into an automated plant control strategy. Estimates of savings on reagent and staffing costs, as well as the benefits from consistent grades and greater recoveries, have shown that the investment in such a system could often be recovered in less than a year.

Jan 1, 1999

By R. Cook

Knowledge based applications are becoming important to Associated Manganese for efficiently dispatching ore of appropriate grades to customers on time. The G2 expert system shell has been used to develop blending and scheduling applications using a combination of object-oriented rule based, procedural, and heuristic approaches. The blending application, for example uses a heuristic approach for creating blends from thousands of small stacks of manganese ore of various grades and sizes, to meet customer specifications while fully exploiting the available inventory. Data capture and data warehousing have become important issues, and the Internet shows strong potential for distribution of pre-processed information.

Jan 1, 1997