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By Richard P. Killmeyer

In 1985 the Pittsburgh Energy Technology Center (PETC) of the U.S. Department of Energy (DOE) conducted a study to evaluate the emerging selective agglomeration processes (Killmeyer, 1985). This paper covers a recent similar study evaluating an associated technology, the emerging advanced froth flotation processes. This study has goals similar to those of the 1985 study: to evaluate the emerging froth flotation technologies collectively and determine how far they have progressed in their ability to clean ultrafine coal, and to assess the differences among the participants. The major concern again in this study was not the level of development, nor the economics of each individual process but only the current technical performance.

Jan 1, 1989

By William A. Dupree, Mark J. Schultz, William J. Francart

Maintaining intake escapeways clear of contaminants from mine fires has been an issue for many years. Removing fire sources from these entries reduces the risk of contamination greatly. In recent years, concerns have been raised related to contamination of the intake escapeways by leakage when fires occur in adjacent airways. This paper discusses measured leakage rates for multiple stoppings at various pressure drops across stopping lines in a number of actual coal mines. Also addressed are methods for reducing the contamination risks for the intake escapeways, considering the ventilation system employed. The Effects of Air Leakage The effects of air leakage through ventilation controls has been well documented. While normal leakage is expected through stoppings, overcasts and other structures, abnormally high leakage results in an inefficient ventilation system and can increase operational costs for a mine. In addition, excessive leakage results in less control over mine ventilation airsplits. This may compromise the isolation of mine escapeways, and allow adjacent entries to be rapidly contaminated by products of combustion in the event of a mine fire. A study was conducted at ten mines in which air pressure and quantity measurements were taken near the active sections. The method used to construct the ventilation controls to separate airways was also noted. Stopping Construction Table 1 shows the type of stopping construction commonly used in the 10 mines included in this study. Main entry stoppings were normally built with mortared joints (wet stacked) with sealant applied to the high pressure side of the stopping. In most cases the entire face of the stoppings were sealed. In one case only the joints between blocks were sealed but the perimeters were sealed in all cases. Some mines also sealed the low pressure side of the stopping. Solid blocks were normally used for main entry construction and hollow blocks were sometimes used for longwall panel development. [ ]

Jan 1, 1993

By Wayne S. Cavender

The geochemical association of arsenic and gold in epithermal precious metal deposits of the Basin and Range province is well documented, and in this paper I wish to discuss the evaluation and utilization of this element association for geochemical gold exploration. In 1961-62, I conducted an exploration program on lands controlled by Getchell Mine, Inc, and centered about the Getchell gold mine itself, Besides exploring for new gold deposits, the program was to evaluate these lands for potential deposits of any type; thus, a multi-phase program encompassing a number of exploration methods was conducted. I shall not elaborate on the process of designing the program or of integrating the various methods, but for gold exploration, geochemical methods were determined to have the best potential. This paper is based on that effort. Figure 1 shows the exploration area, which covers the northern half of the Osgood Mountains in eastern Humboldt County, Nevada. The Getchell $line is on the east flank of the range and is about 40 miles northeast of Winnemucca.

Jan 1, 1964

The need for an integrated approach to optimization of unit operations in both the pit and the mill has long been recognized, but the complexity and nature of the overall problem has up to now resisted solution. This paper reports on a modeling methodology which couples symbolic and numeric computing to unify operations in both the pit and mill. The ultimate goal of this work is to optimize all operations that are influenced by blasting. Blasting plays a key role in all facets of operations. Obviously, drilling and blasting costs are determined by blast design, but the down-stream costs that are closely related to blasting results are often treated as separate functions: loading, hauling, cleanup, and crushing and grinding are all heavily influenced. Diggablilty and bucket fill factor are a function of fragmentation, the condition of the floor and uniformity in the shape of the muck pile. Likewise, cycle times and loading delays partially determine haul cycles, while fragmentation distribution and size determines the efficiency of truck loading. Removal and breakage of oversize causes loading delays and increases cleanup costs. The influence of blasting doesn't stop at the crusher. Mill productivity, power consumption, and maintenance are a function of the feed. Even at the SAG mill a reduction of a critical particle size during blasting can increase throughput. Thus, a bottle-neck for production far removed from unit operations in the pit can be alleviated by a modification in blast design. The question is: how do we optimize blasting with respect not only to itself but to al\ related mining and milling operations? For that matter, how do we even model blasting so that we can control the results of a blast?

Jan 1, 1991

By Theophilus Mensah, Kwame Awuah-Offei

Engineers face significant challenges when determining what geometry provides the most profitable and safe stope for extraction. Several techniques and optimization algorithms have been developed in recent years, but most fail to find optimal solutions because they are heuristic or LP-based without efficient geometric constraints. This paper presents a two-dimensional binary linear programming (BLP) model for determining the optimal combination of blocks in a stope that maximizes the economic value of the layout of stopes for a sublevel deposit. The work draws from Queyranne and Wolsey’s (2017 & 2018) formulations of tight constraints for bounded up/down times in production planning problems to formulate novel and efficient geometric constraints along with geotechnical and grade constraints for the BLP stope layout optimization problem. Results from the model indicate that it is possible to formulate efficient shape constraints in LP-based approaches. The model used for the numerical example contained 144 valuable blocks out of 774 blocks, which translates into an economic value of $53.21M. The BLP model selected 60 valuable blocks and 13 waste blocks that met all constraints translating into a maximum economic value of $34.4M in 1.83 hours within a gap tolerance of 0.00%.

Jun 25, 2023

By K. L. Woodruff

Shredding is the usual first step in processing municipal solid waste (MSW) for resource recovery. This unit process requires high capital cost and, usually, considerable maintenance cost. In addition, some shredders at times will render certain components of the MSW in a form difficult to recover. This is particularly true in the way metal cans are distorted and the way glass is pulverized. A trommel screen was proposed (1) to pre-process packer truck refuse prior to shredding. Part of the logic for this step is that the portion of raw refuse already within the specified shredder output particle size range would bypass the primary shredder and proceed directly to further processing, such as to an air classifier or secondary shredder. This would reduce the throughput of the primary shredder and allow certain recoverable materials, such as glass, to remain in larger piece sizes, important for recovery. In this way, operating costs for the shredder would be reduced and the recoverability of materials, and hence the revenue, increased.

Jan 1, 1975

By Dennis C. Drehmel

Because of their relatively low cost, carbonate rocks are desirable in abatement of air pollution by acid gases. Although many processes and types of equipment have been proposed to control or prevent the emission of acid gases, this paper considers only three: dry-limestone injection, wet-limestone scrubbing, and chemically active fluid beds. For the dry-limestone-injection process, surface area-especially from pores in the 0. 2- to 0.3-micron range-is one of the important parameters which will discriminate between less and more reactive carbonate rocks. Marls, chalks, oolitic calcites, and other fine- grained limestones show larger-than-average surface areas and better- than-average removal efficiencies. Inert chemical impurities such as silica detract from reactivity. A dolomite is not necessarily less re- active than a calcite. For the wet-limestone-scrubbing process, dissolution rate of the carbonate rock controls the differences in stone reactivity. In this process the dolomites are less reactive than the calcites. In addition, more than 90 percent of the dolomitic impurity in Fredonia white lime- stone is inert during limestone scrubbing. Dissolution rate is also a function of particle size for large-grained carbonate rocks. Fine grinding of such rocks will increase the dissolution rate to that of a fine-grained rock. Hence the requirement of high dissolution rates may be met by some grinding of fine-grained material (e. g., marl, chalk, or other limestone) or by fine grinding of coarser grained material. For chemically active fluid beds, chalks have the best capacity to absorb both SO2 and H2S. However, most chalks are probably unsuitable for fluid beds because of high attrition rates. Because dolomites are generally more reactive than calcites with both SO2 and H2S, a dolomite would be the feed material of choice for a chemically active fluid bed.

Jan 1, 1974

By Caroline Gerwig, Joseph R. Wickline, Zach Agioutantis

In longwall mining, the progressive caving of the roof allows stored energy to dissipate over an extended time. However, in some cases, the roof strata above the longwall panel are unusually strong and do not break with the movement of the working face. Instead, the roof material bridges over the expanse of the longwall, forming an unstable beam. Later, when this beam breaks, the stored energy can release suddenly, causing a seismic event to propagate to surrounding mine workings. The focus of this paper is to estimate the size of beams that form over longwall panels to the seismic energy recorded by the mine. Analytical calculations are used to verify two-dimensional models of longwall roof beams to determine the strain energy and gravitational energy developed, which is then released upon strata failure to surrounding mine workings. Models are developed using RS2 to model the stress, strain, and deflection along the bottom of the longwall roof beam to calculate gravitational and strain energies. Gravitational energy is shown to be the main driving factor in energy release, except for the beams with low heights. Analyses allow the determination of beam characteristics based on seismic data. The analysis is refined using swelling factor to compare various beam drop heights. The models show an increase in seismic magnitude for higher drop heights. However, the actual data provided by the Buchanan mine displays a decrease in seismic magnitude with increasing drop height, indicating that energy is dissipated into the broken gob material as drop height increases.

Jul 1, 2023

By R. A. MacGregor

The Stanreck mine of Stanreck Uranium Mines Limited in located on Quirks Lake in the Elliot lake - Blind River area of Northern Ontario. It is approximately 25 miles north of the north shore of Lake Huron, equidistant between the cities of Sudbury and Sault Ste. Marie. The property was developed ad brought into production at a rate of 3,000 tens of ore/day during the uranium boom of the mid 1950's. By 1960 mine waters were becoming quite acid through the activity of bacteria. Treatment of this water was begun for pollution control and a small amount of uranium which had been leached from the ore by these acid waters was recovered. Development of bacterial leaching with a view to increasing production by this method commenced in December 1962. Subsequently, it was succeesfull in producing 10,000 - 15,000 lbs. of U308/month. Since late 1964 uranium production has been obtained solely from bacterial leaching. A rare earth concentrate was also made for its yttrium content during 1966 and 1967. This paper describes the development, operation and methods used in the underground bacterial leaching process.

Jan 1, 1969

By A. G. Taylor

High value materials, such as gold, platinum and other precious metals are subject to loss through unauthorized removal from mines, smelters, refiners, and other places where such materials are processed. A study published in 20011 determined that between 1994 and 1998 an average of 603 kilograms of gold per year was stolen from South African miners and subsequently recovered. This does not include the gold that was stolen but not recovered. At 2011 prices, 603 kilograms of gold would be worth approximately $33 million. Mine security personnel believe that the unrecovered stolen gold far exceeds what is recovered2. Traditionally, metal detectors have been used to screen personnel leaving secure areas to discourage such unauthorized removal. However, with the current near-record prices of gold, platinum, and other precious metals, it has become worthwhile for people exiting a facility to walk out with quantities of product that are too small for ordinary metal detectors to register, resulting in substantial financial losses.

Jan 1, 2012

By W. G. Pariseau

"BACKGROUND Strata mechanics of three underground coal mines in central Utah were recently studied using a specialized finite element technique [1, 2, 3, 4]. The purpose of these studies was to examine relationships between mining and related seismicity. The longwall mining method was predominant, but room and pillar mining and barrier pillar mining were also used in the mines studied. In every case, high correlation between face advance and seismicity was observed. The specialized finite element technique allows for whole mine subsidence estimation at a kilometer scale and for stress concentration at a meter scale near a working face. Comparisons of observed mine subsidence with model subsidence allows for model verification and justifies detailed analysis of the evolution of stress at seam level. Yielding is expected near a longwall panel face and as the face is advanced the extent of yielding is expected to increase. The total number of element failures in a finite element mine model also increases, so a high correlation with associated seismicity, say, event count, is not so surprising. A brief review of recent coal mine studies in Utah is presented in the sequel. The procedures are given in some detail in application to trona mining. COAL MINES The analysis procedure begins with the geologic column and proceeds to specification of strata properties including elastic moduli and strengths. Joints are an integral part of the geologic model and joint set specifications include dip direction, dip, spacing, stiffness and strength. Spatial variability of strata properties in situ may be taken into account during analysis. Topography is important, especially to Utah coal mines that are developed from outcrop in regions of high relief. Mesh generation follows specification of data input. Finite element analysis is next, followed by reporting of results. In this regard, all finite element computations are based on first principles. No model “calibration” is done that involves adjusting computer input to obtain a fit to mine measurements such as subsidence profiles. Figure 1 illustrates the concept of a dual node – dual mesh finite element concept. Dual nodes are roof and floor nodes in mined areas. These nodes replace the seam. The dual mesh is a much refined mesh with displacement boundary conditions obtained from the big mesh and thus replaces the effect of mining in the region outside the dual mesh. The refined dual mesh allows for details of stress, strain and displacement near a working face of interest. Strata Properties Strata properties include elastic moduli and strengths of intact rock between joints and joint stiffness and strength for each joint set present. Both properties sets may be obtained from laboratory test data, although testing joints poses a sampling problem in the field. The statistical variability observed in laboratory test data, say, in unconfined compressive strength tests is often characterized by much variation. In fact, the coefficient of variation, ratio of standard deviation to mean, is often greater than 35 percent. When sample values are mapped back to the mine location, one may observe spatial variability as properties vary from place to place as shown in Figure 2. Spatial variability may be incorporated into a finite element analysis with probabilistic assignment of properties to elements in accordance with measured variability. The result is a more realistic model of rock in situ."

Jan 1, 2017

By D. W. McGlashan

Zeta potential changes were determined as a function of pH, metal ion, and surfactant concentrations. Prom the analysis of data, flotation experiments were carried out to correlate float-ability with the differences in zeta potential. Cassiterite in water bears a negative zeta potential, The zeta potential of cassiterite is sensitive to pH changes; the electric double layer arises from the preferential adsorption of H+ and OH- ions and subsequent ionization of the hydroxylated surface. It is suspected that hydronium-ion concentration may cause reversal in the sign of the zeta potential. The ZPC was found to occur at pH 3.4. Metallic ions and the hydrated ions thereof affect the zeta potential of cassiterite in differing degrees of intensity. Without prior activation, sulfonated surfactants do not change the zeta potential of cassiterite. Sodium alkyl aryl sulfonate is especially active on lead-activated cassiterite and ferric-activated cassiteriten Microcalorimetric fiests confimed the activity of ions on cassiterite and showed the hydrated character of cassiterite smfaces. Close correlation between zeta potential and microflotation results was achieved.

Jan 1, 1969

By D. A. Robbins

The application of remote sensing for environmental measurements is already being utilized. Aircraft mounted imaging spectroscopy has been utilized to evaluate areas of historical mining operations as well as active mine sites. To the extent that remote sensing can provide more sensitive, cost effective, and timely monitoring potential, the technology is of interest to the industry. Questions remain about the application and validation of the data and the availability of the technology in the private sector. This presentation will discuss some of the potential uses, benefits, and concerns related to remote sensing and efforts to monitor the technology's development.

Jan 1, 1999

By C. Braux

The aim of this study was to develop an integrated approach to enable identification of areas favourable for the presence of massive sulphide deposits in a given region (Las Herrerias, Spain). It is based on geochemical soil exploration, geophysical surveying (ground gravimetry), detailed geological mapping and a knowledge of the deposits of the South Iberian Massive Sulphide Belt. The multi-dataset approach consists, in the first instance, in standardizing and combining all the geochemical data with reference to their geological setting. Next, the "heavy" anomalies are extracted from the gravimetric survey, regardless of the surrounding context (heavy or light). The results from these two stages are then crossed, so that areas where heavy anomalies are associated with geochemical anomalies can be identified and classified. Crossing the geochemical and geophysical data enables a much tighter selection of anomalies than does the manual superposition of data provided by each method (geology, geophysics, geochemistry).

Jan 1, 1994

By A. P. Wickland

The characteristic problems related to drilling a hole for evaluation of an orebody are generally quite similar, whether we're drilling a core hole, or a hole to obtain chip samples. The basic objective in each case is fundamentally an economic factor; to produce the maximum amount of usable information per hole at a reasonable footage price. The success of the drilled hole depends largely upon the amount of investigation and research spent on the prospective area and the ability to forecast the capable personnel needed plus the right kind of drills, ancillary equipment such as bits, muds and various additives necessary to make the drilling program successful. The driller is confronted with a wide variation of drilling problems due to the nature of subsurface conditions. Some of these problems are: overburden, which may consist of clays; sand; boulders; or glacial till. These surface conditions may exist up to 2,000 feet in depth and upon reaching bedrock, formations may consist of swelling shales, broken sandstones, and every conceivable rock-type, coupled with every known structural problem such as dips, faults, folds, etc., and to this added extras such as permafrost and/or ground water problems combine to increase the necessity why an understanding of the problems along with the proper reaction of the driller plus the formula to compensate for ground conditions is necessary to complete a drill hole. Since most geologists are familiar with diamond core drilling techniques, I would like to discuss other methods used in evaluating ore deposits.

Jan 1, 1973

By K. G. Kebkal, R. Bannasch

"Because the operation of tethered underwater vehicles in the deep ocean or under drifting ice areas is very complicated or impossible, the application of autonomous underwater vehicles (AUV) is preferred or even the only possible solution. However, this implies the possibility of a direct and real-time control over all AUV functions, which is only achievable with the availability of accurate positioning/navigation and a high-speed communication link. This paper presents a flexible bottom- or surface-based solution enabling high positioning accuracy of underwater objects (harvester, AUVs, bottom nodes); specifically, a multifunctional system that combines Ultra Short Baseline (USBL) transceivers and Long BaseLine (LBL) stations deployed at a large depth. Moreover, each baseline transponder is equipped with a high-speed communication device to provide the means for real-time AUV control based on the information about its current position, e.g. navigate it with direct commands and operating its actuators and other mechanisms. Moreover a communication link with a high data rate can provide valuable visual information from the operation area.Depending on how many nodes the LBL grid comprise has, target transponder positions can be estimated with an accuracy of several to tens of centimetres. The purpose of the paper is to present the experiments with all key elements of the multifunctional Hydro-Acoustic USBL-aided LBL Positioning and Communication System."

Sep 1, 2014

By S. K. Nicol

Flotation, water-washing cyclones (hydrocyclones) and spiral concentrators are the three process units most commonly utilised in fine coal preparation. The results of testwork conducted on these three units will be presented and their performance and separation characteristics examined in detail. In particular, the dependence of the separation characteristics of each unit on particle size and the constraint this places on product quality (ash and sulphur levels) will be discussed. This dependence will be shown to be a critical criterion in the selection of fine coal circuits.

Jan 1, 1986

By M. A. Ackerson, R. E. Griffin, W. H. Pomroy

Two automated fire detection system configurations have been used successfully in underground mines: the pneumatic "tube bundle" approach and the electronic telemetry approach. The electronic telemetry approach is more widely used, owing to its greater speed, flexibility, and capacity to both monitor other underground conditions, and remotely control underground equipment. However, depending on specific mine conditions and layouts, pneumatic detection, or a combined pneumatic/telemetered system may offer significant advantages over the telemetered approach alone. This paper describes research by the U.S. Bureau of Mines to design and in- mine test a rapid response pneumatic fire detection system tailored to the unique requirements of multilevel metal mines. The relative merits of pneumatic detection are discussed in the context of typical multilevel mine layouts and environments. A Bureau developed proto- type system is described with emphasis on design features which counter commonly perceived and/or experienced pneumatic detection system operating problems. Finally, the results of a 3-yr in-mine performance evaluation of the prototype hardware are discussed. Included are descriptions of system layout and coverage, response time, tube leakage, sample dilution, elimination of accumulated water from sample lines, and system maintenance and reliability.

Jan 1, 1989

By Richard R. Radel, Jack Barry

Contract required excavating 2,000 If of 14' horseshoe tunnel in rock, a 95' deep work shaft on shore, and a 50' deep intake shaft located in the middle of the Niagara River just above Niagara Falls. Large quantities of H2S were encountered in the range of 20 PPM with ventilation. Peak levels of 40 PPM were recorded. The original designed ventilation system required only a volume of 10,000 CFM to meet OSHA requirements. The volume of air was increased to 50,000 CFM to dilute the H2S to al- low workmen to work and comply with OSHA H2S action levels. The second phase of the tunnel consisted of placing 72" ID X 20 foot long concrete reinforced pipe in the tunnel. When the tunnel was holed through and both shafts were open, a substantial amount of work was required to take place in the shafts which eliminated the possibility of placing a bulkhead to secure proper ventilation. The ventilation team designed a jet system airlock. The design of this system was to bring fresh air down the work shaft in two duct systems; one 30" diameter and one 24" diameter. Following the excellent work of Jan Wolski (7th Mine Ventilation Symposium chapter 58) our design incorporated nozzles located approximately 100' in by the work shaft. The velocity of the 24" diameter duct was 6,365 FPMD2.2 MPH. The velocity of the 30" diameter duct was 6,117 FPMl69.5 MPH. Both systems were on blow and being that air expands at 3112 degrees per side this high velocity of air expanded and created an air bulk head through which men and the large sections of concrete pipe could be passed without any delay or additional cost to the project.

Jan 1, 1997

By Danforth R. Hale

The pressure of military use of quartz resonators led to efforts to Grow high, grade quartz crystals in Germany and in Great Britain during 19)3-25, and was responsible for a series of U.S.A. Signal Corps contracts beginning in 1946 with the Clevite Corporation (as the former Brush Development Company), Bell Telephone Laboratories, Antich College, and others. The technique of growing crystals from the melt, such as KI, NaBr, was already commercially inuse Quartz could not be so grown, since its utility depends on the form stable below 573°C, and, even if it could be grown from an extraordinarily viscous melt, the higher form passing through this transition becomes twinned. Again, several crystals were being grown commercially from water solutions; quartz, however, is listed in the common literature as being insoluble in water. Fused quartz, or vitreous silica, was chosen as raw mater¬ial by the European experimenters because of its thermodynamically lesser stability than quartz, and various alkaline solutions were tried for the purpose of enhancing the solubility.

Jan 1, 1964