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By S. J. Schatzel, J. D. Addis, V. Gangrade, L. L. Chasko, C. A. Hollerich

A ventilation study was conducted at a western U.S. coal mine to evaluate the movement of longwall face air and exchanges between the face and worked-out areas to document the presence or absence of face airflow pathways between these locations. This field study was part of a project investigating the effect of longwall face length and caving characteristics on longwall face air behavior and its potential movement on and off of the face. Tracer gas experiments using sulfur hexafluoride (SF6) were done to describe air movement on the face and in the mined-portion of the active panel. Maintaining adequate ventilation air on longwall faces is important for worker safety and for the dilution of methane emitted from the face and caved gob.

By J. L. Post

A near-surface body of readily available Na-montmorillonite is located about 24 km (15 miles) southeast of Fallon, NV. The clay, which forms an irregular deposit about 4.8 km (3 miles) long, lies in altered rhyolite within a fault zone. The clay is similar to Wyoming bentonite but is less uniform in composition and contains less MgO and more Fe2O3 in its crystal structure. The clay interlayer cation population can be estimated by using a modified DTA procedure. With selective mining, the industrial properties of the Nevada clay are adequate for use as drilling mud, in foundry applications and as a sealant for hazardous wastes and canals.

Jan 1, 1997

By R. R. Fernández

The Newmont roasting plant in Carlin, Nevada, commenced operating in December 1994. Over the years, refractory ores and pyrite concentrates from different gold deposits constituted the feed to the facilities. Historical plant performance indicated that the roasting temperature was the main variable affecting the structural characteristics of the calcine, which in turn affected the recovery of gold by cyanidation. Gold recovery as a function of roaster temperature has been closely monitored since October 2000. The original design temperature was 550° C. Lower roaster temperatures of around 500° C resulted in a gold recovery increase of more than six percent. This increase was directly related to an increase of the surface area of the calcine. The implementation of an ?intelligent? process control system helped significantly in achieving steady low roasting temperatures, thus obtaining high gold recoveries of 92 to 93 percent. Under these conditions, several roasting campaigns with high-arsenic-containing ores were conducted, which resulted in a significant decrease in gold recovery. The reduced gold recovery was caused by the loss of surface area (e.g., porosity) of the calcine as the arsenic content of the roaster feed increased.

Jan 1, 2010

By Giuseppe Gaspari, Xiangrong Wang

The pandemic emergency is forcing transit agencies to define strategies allowing social distancing, which are more challenging in underground interchange stations in crowded downtown cores. Toronto Transit Commission’s (TTC’s) Bloor-Yonge Station Capacity Improvement Project in Toronto was approved to meet increasing demand and represents an opportunity to fight COVID-19. This paper discusses cost-effective solutions in expanding the cut-and-cover station box over the existing Toronto Subway Line 2 and connecting it through ventilation openings in the cast-iron tunnel liner. Potential uplift risks and structural damage due to minimal vertical clearance were analyzed via three-dimensional finite element analyses with advanced constitutive laws to simulate the multi-stage construction process. Based on the simulation results, a series of countermeasures, including excavation support systems, king posts, ground-consolidations, and liner reinforcements were integrated into comprehensive design options to ensure the serviceability and structural integrity of the subway tunnels.

Jun 13, 2021

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

By K. Katen

In another situation, Dave Zegeer, the Assistant Secretary of Labor for Mine Safety and Health, whom all of you know very well, would have taken the opportunity to talk with you. In his absence, however, I would like to reference some of his recent comments which may help us to see the issue of mine safety in historical perspective. Dave pointed out that this year is the eightieth anniversary of the Great Earthquake and Fire of San Francisco. The whole world heard about that disaster--it and the 452 people who died in it. In that same year, nearly five times as many people died in coal mines, but no one particularly noticed.

Jan 1, 1986

By Stanley C. Suboleski, C. B. Manula

INTRODUCTION In any mining operation all possible steps should be taken to increase efficiency. One area for improvement is mine planning and design, particularly in the area of equipment selection for room-and-pillar systems. Be- cause of the availability of a wide variety of face machines, a fair degree of selectivity can be exercised in the choice of equipment for a particular job. However, this choice must be made on the basis of quantitative facts and forecasts related to the mining application. The purpose of this section is to develop and analyze the details of the mining process. Some specific areas studied include the relationship of system design to productivity, suboptimization as a result of equipment changes, and measurement of system performance. The plan of work leading to a quantitative description of these study areas is based on the growing interest in total system design using simulation as an analytical method (Manula, 1963). CHARACTERISTICS OF PRODUCTION OPERATIONS FROM ROOM-AND-PILLAR SECTIONS For a given mining method, raw production in a given section of a mine is primarily dependent upon the coal seam thickness, roof and floor conditions, methane emission, the mining methods, and the man-machine element. Average section production varies from 300 to 800 st per shift for conventional and continuous mining in high seams and from less than 100 to 300 st per shift in low seams. Since the reject varies from 0 to 40%, these figures must be decreased by the appropriate percentage to reflect the amount of clean coal mined. Personnel requirements per production section per shift for the various methods are listed in Table 1. Table 1. Production Personnel Method No. Method No. Conventional 12-1 5 Longwall 9-14 Continuous 9-1 2 Shortwall 9-12 MINING VARIABLES To evaluate the constraints and interrelationships for various mining methods, it is necessary to categorize the variables which underlie system production potential. Seven critical independent variables which determine production can be identified and categorized (Suboleski, 1978) : Seam Height The five categories are as follows: less than 36 in.;. 36 to 55 in.; 55 to 100 in.; 100 to 180 in.; and greater than 180 in. Floor Quality Floor quality ranges from : Excellent: Smooth, hard, grades less than 1 to 1 % % , and dry. Good: Smooth, soft but dry, with grades less than 3 % . The floor will deteriorate, but cautious operation can prevent it. There may possibly be heaving at some later time. Fair. Soft and damp. There is occasional interference with equipment operation; requires the use of four-wheel drive shuttle cars; ruts with regular use, and may have adverse grades of 5 to 7%. This may be coupled with slippery bottom and/or occasional steep rolls. Poor: Soft and wet. Requires blocking of the bottom to support equipment. There are frequent steep rolls and grades in excess of 7%. Roof Quality Roof quality ranges from : Excellent: Men are able to work under the unsupported top during the initial production cycle if legally permitted. Good: The roof is bolted on a 4 x 4 or 5 x 5 pattern with short bolts (442 in.) or <seam height if the seam >42 in., or requires posting with no bolts on a 4 x 4 or 5 x 5 pattern. There are no falls. Average: The roof is normally bolted on a 4 x 4 or 5 x 5 pattern, but with long bolts (>seam height or >6 ft.). There are infrequent minor falls or there may be an excellent roof which is difficult to drill. Fair: This type often requires spot bolting in addition to the regular pattern or bolting with planks. The roof conditions require shorter than planned cuts, or narrow cuts. Poor: This type requires bolts plus crossbars and posts, or installation of yielding supports or truss-type support. It is almost certain to fall if this is not done. Methane Liberation This ranges from none detected to low (no buildup at the face, even with minimum ventilation requirements) to moderate (the curtains must be extremely tight and tubing close to the face or methane will build up to 1 % during the loading of the car) to high (methane will build up to 170 if the miner is operated at the normal rate, even with proper ventilation). Hardness of Coal Coal hardness falls into the following categories: Soft: Soft coal is easily cut by a continuous miner. A plow could be used by longwall. Average: Coal of average hardness could be easily cut by a miner, and a shearer would be used in the longwall. Moderate: Moderately hard coal causes difficult cut-

Jan 1, 1982

By Matthew E. Eisenmann, Gerald H. Luttrell

Performance data from phosphate plants are often untrustworthy because of difficulties associated with highly variable feeds and unstable equipment operation. In some cases, this problem is further compounded by improper sampling procedures and unreliable laboratory analyses. Questionable data often lead to misleading conclusions that result in lost productivity and profits. Data reliability may be checked using mass balances, but the mathematics associated with this procedure can be overwhelming when multiple data sets or complex circuits are evaluated. To overcome this problem, a simple spreadsheet-based mass balance program has been developed specifically for plant operators. To use this program, operators simply enter a description of their circuit and input the assay values (e.g., % BPL, % Insol, etc.) for each stream. The program then generates the best estimates of the assay values and flags values that may be unreliable. The spreadsheet is specifically designed to be easy to use and requires no knowledge of statistics or programming. This manuscript reviews the mass balance problem and describes how spreadsheet programs can be used to evaluate plant data. An example problem involving the analysis of data around a two-stage phosphate flotation circuit is presented.

Jan 1, 2002

By SAHENDRA SINGH, SANJIT KUMAR PAL, DHARMITA HORO

This study was carried out in Ichadih to map the sulfide/gold mineralization using combined electrical resistivity tomography (ERT) and self-potential (SP) methods. No geophysical analysis has been carried out to delineate such ore deposits in the area. Thus, the study provides a different approach for approximate location and extension of the quartz reef associated with sulfide/gold mineralization. It also provides the elementary idea for further detailed subsurface investigation in terms of geological and geophysical approach. 

By J. D. Miller, C. L. Lin, J. Dong

Nano clay mineral particles such as kaolinite — with primary particles typically smaller than 2 μm in size — can cause significant problems in flotation processes and tailings disposal, including the processing of Florida phosphate rock and Canadian oil sands. In this study, the consolidated state of flocculated kaolinite sediment was examined, and high-resolution X-ray microtomography (HRXMT) was applied to describe the structure of the consolidated sediment. Using this tomographic information, the complex geometry of the channel network structure for the consolidated flocs was established for the first time. With the establishment of the experimental channel network structure, permeabilities were estimated by flow simulation using the Lattice Boltzmann method. Results for kaolinite sediment with and without polymer are compared and discussed. Results for flocculated kaolinite sediment in a gravitational field are also presented and discussed. The results show that as polymer dosage increases, the permeability of flocculated kaolinite sediment increases, and as suspension pH increases, the permeability of flocculated kaolinite sediment decreases.

By Scott Burchmore, Jason Emery, Michael Melville

This paper presents best practice data management for monitoring of extensometers in Australian underground coal mines. This work is based on the combined experience of the authors and the available literature. The information and ideas presented herein are a culmination of many years of database development founded from mine site-based ground support design, underground inspections, extensometer data management and data analysis. Each author has more than ten years’ experience as a practicing geotechnical engineer at several operating industry wide research project focused on utilizing mechanical extensometer data for data analytics and machine learning. Principal hazard ground control management plans, stipulated in Australian coal mining legislation, outline the mandatory installation of ground monitoring devices during routine mining activities. After 20+ years of data gathering the barrier to implementing modern data analytics remains the challenges imposed by inconsistent data structure and data quality. This inconsistency is still routinely found between sites, companies and mining regions. Through the relatively simple application of a standardized database structure, the potential to shift from simplistic tracking of trigger levels, siloed at individual sites, to an industry standard method for compilation & comparison of monitoring data is enabled.

Jun 25, 2024

By S. L. Bessinger

In the design and specification of a ventilation system for an underground mine, it is necessary to make reasonably accurate estimates of the pressure losses in the various airways of the mine. These estimates can be made with little difficulty for open airways with simple geometric cross-sections, such as those cut by continuous miners or tunnel-boring machines. The situation is much different on a longwall face, where the airway&apos;s complex geometric cross-section and the presence in the airway of obstructing equipment having a variety of shapes make it difficult, if not impossible, to estimate pressure loss using traditional methods of calculation. Headlosses in mine entries are calculated using Atkinson&apos;s Equation (1). [H = (English) H = (SI) (1)] where H = pressure ,loss, in. of H20 (Pa) K = friction factor, lbf min2/ft"4(Kg/m3) P = perimeter, ft. (m) L = airway length, ft (m) Q = airflow quantity, ft3/min (m3/sec) A = flow cross sectional area, ft2 (m2)

Jan 1, 1987

By M. P. Corriveau

This is the case history of how two nearby plants in Southwest Virginia solved their water clarification problems. While the solutions should not be considered applicable industry-wide, the methods used in arriving at the answers deserve consideration. When Clinchfield&apos;s Moss No. 2 Preparation Plant, the first ever built in Tiller Seam coal, was started in the fall of 1956, the clays in the raw coal soon posed a flocculation problem, Laboratory sedimentation tests were initiated; and as a result, lime was adopted as the flocculant for the clays, With lime, a pH of 11.2 was required. As the plant tonnage increased, it became evident that the amount of coal fines produced in the mining and preparation was greater than had been estimated and that the 90-foot thickener was inadequate in providing sufficient settling time to effect a clarified overflow for reuse. Testing showed that Separan 26105 (NP10)1/, when used with lime, was the most satisfactory coal flocculant available,

Jan 1, 1960

By K. Hanumantha Rao, K. S. E. Forssberg, F. Su

The influence of reagents dosage, pH, temperature, and particle size on the kinetics of apatite flotation response from magnetite has been investigated. The first-order models characterizing rectangular distribution and fast and slow distributions (F-S model) of floatabilities gave an excellent fit to the results of apatite flotation when compared to other models. However, the latter model is found to be better than the former in the goodness of fit and also in the description of flotation performance. The kinetic parameters in the F-S model are estimated by using a nonlinear least squares fitting program. The ratio of fast and slow rate constants is observed to be an important parameter for identifying the optimum levels of the variables and to outline the selectivity between apatite and magnetite. The influence of collector dosage is realized from the model parameters by relating it to the fraction of slow- floating particles. An attempt has been made to describe the apatite flotation behavior with the determined model parameters.

Jan 1, 1999

By Fernando Pendás, Jorge Loredo, Alumudena Ordóñez

Water derived from mine-tailings typically contains high concentrations of H+, SO4, Fe and other metals, and it frequently suffers a decline in pH and the development of acidic mine drainage (AMD). A paper describing the results of a series of laboratory experiments with real AMD and a subsequent field trial with a in situ pilot system to assess a potential method for remediating tailings-derived water is presented here. After testing different organic substrates, residence times and flow conditions during two years to determine the most appropriate treatment for a polluted Spanish AMD, a pilot scale system combining SAPS, ALD, oxidation/sedimentation ponds and an anaerobic wetland was designed. Preliminary analyses of effluent samples indicate acidity and metal removal is occurring within the system, although sulphate removal is not complete. The results of this small-scale field trial suggest a potential cheap, long-term alternative for remediation of acid mine drainage.

Jan 1, 2000

By M. J. Laurila

Simulation of coal preparation circuits is becoming a widely practiced technique used for the design of coal preparation plants. On a much more limited basis, simulators are finding application in off-line process control. A typical application in the latter category involves inputting projected coal washability data for a shift into the simulator and using the software to optimize product quality and recovery within a range of predefined specifications. The plant is then operated at SG?s of separation determined from the simulation exercise for the one shift time period. This procedure is useful in that it incorporates some form of advanced planning into preparation plant operations. There is an attempt made to reflect changes in feed coal quality on a shift by shift basis rather than continually running the plant near design specifications with changes in SG?s of separation being made in response to an inadequate sampling program which only provides a spot measurement of material that has already passed through the plant. Instead of instituting changes on a shift by shift basis, NHI has proposed a method whereby monitoring three major operating parameters, * Feedrate to jig * Flowrate from hydrocyclone overflow * Density from cyclone overflow the ongoing plant operating performance can be accurately predicted on a continual basis, i.e., updated hourly. Using a distribution curve to predict the split between the clean coal and refuse from a given separator does not account for variations in efficiency that occur as a result of variations in operating parameters. NHI and Arch have studied the effect of both jig loading and solids content in the recirculating load to the jig on product quality. As a result, relatively simple measurements can be made on-line in a preparation plant which will provide input data to the simulation program that enables the prediction of jig/hydrocyclone circuit performance on a real time basis.

Jan 1, 1985

By R. Woods, J. D. Wright

INTRODUCTION The Endako deposit was first explored in 1926, but development waited until the early nineteen sixties. It first came under the control of Placer Development in 1963, and early in 1964 a decision to bring it into production was reached. The deposit is located near the geographic center of British Columbia, and is served by an east-west communication system including a paved highway, mainline railway and good telephone, teletype, and computer facilities. The plant area is shown in Figure 1. The operation is known as the Endako Mines Division of Canex Placer Limited of Vancouver. First production was achieved in June, 1965, at a nominal rate of 10,000 tons per day, but it soon was closer to 15,000 tons per day. In 1967, two new grinding and flotation sections brought capacity to the present rate of approximately 27,000 tons per day. With mill heads of around 0.15 percent MoS2, production is about 14,000,000 pounds of molybdenum per year. A flowsheet of the operation is given in Figure 2. A legend for this flowsheet is given in Table 1. Published ore reserves are estimated at 214,500,000 tons at an average grade of 0.143 percent MoS2. PRIMARY CRUSHING The 85 or 100-ton haulage trucks dump over a grizzly into a 42 inch x 65 inch C.A.C. (Canadian Allis Chalmers) gyratory crusher.

Jan 1, 1976

Surface characterization techniques, i.e. contact angle measurement, atomic force microscopy (AFM) surface force and surface imaging measurement, were applied to investigate the molybdenite surface in aqueous solution. It was shown that the cleaved basal surface of molybdenite was very hydrophobic with a 92 degree water contact angle. The non-polar component of the solid surface free energy is 50.52 mJ/m2 while the polar components are almost zero. The solid surface was not reactive and was only weakly charged at the pH 6. When the aqueous media changes from water to 1×10-4 M KEX solution, the measured contact angle, adhesion force and surface roughness all increase slightly. However, ethanol rinsing made the surface change back to the bare substrate. It was suggested that the hydrophobic chemical, i.e. dixanthogen, which was shown in the morphology of patches by the AFM image, physically adsorbed on the hydrophobic molybdenite surface through the hydrophobic interaction.

Jan 1, 2009

By S. K. Kawatra, C. A. Hardison, J. Gurtler, T. C. Eisele, K. Lewandowski

Acid soak tests were used to measure the effectiveness of binders in highly acidic conditions to determine their suitability for use in copper heap leaching. Soak tests involved placing the agglomerates on a screen, soaking them in a solution that replicates the pH of the raffinate used in a heap leach, and measuring the quantity of fine particles that passed through the screen. A wide range of binders were evaluated which had potential for functioning in acidic solution. Only a few binders were effective, with the best-performing binders being nonionic polymers designed for dust suppression applications. The most effective binder prevented all but 1.86% of the fines from being released and passing through the screen, while binderless agglomerates allowed as much as 29% of the fines to pass through the screen. The soak test developed for this study provides a useful method for rapidly identifying promising binders at a low cost, and for examining effects such as curing conditions on agglomerate quality.

Jan 1, 2005

By F. Vincent, A. Boulet, M. Noaparast, F. Woodcock, A. R. Laplante

A novel methodology to estimate gold recovery by gravity is presented. It makes use of a population balance model which represents gold liberation, breakage and classification behaviour and applies pre-concentration and recovery data to gravity recoverable gold (GRG) to predict overall recovery. The methodology is designed for gravity circuits located in the circulating load of secondary grinding mills. Gold liberation is estimated by processing a sample of representative ore with a laboratory Knelson Concentrator (LKC) in three successive steps, each at a finer grind than the previous one. Breakage behaviour is represented by a matrix H, which redistributes GRG in the feed of the secondary mill in the various size classes of its discharge. Provision is also made to account for gold overgrinding, which decreases the overall amount of GRG. Classification, pre-concentration and recovery data are estimated from plant performance, and are represented by the diagonal matrices C, P and R. The methodology is demonstrated with case studies of greenfield, retrofit and optimization applications.

Jan 1, 1995