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By S. Banisi, A. Ghasemi, E. Nematollahi

Discrete element method (DEM) has been used as a popular simulation method to verify designs by visualising how material will flow through complex equipment geometries. Although DEM simulation is a powerful design tool, finding a DEM model which includes real material properties (e.g., shape, cohesion and friction coefficients) is not computationally feasible. In order to obtain more realistic results, particle energy loss due to rolling friction has been highlighted by many researchers. To implement a reverse torque to account for rolling friction, various models have been proposed. On account of the complexity of the problem, there is no unique model for all applications (i.e. dynamic and pseudo-static regimes). In this paper, an in-house developed DEM software (KMPCDEM ©) was used to assess the robustness of three commonly used models by comparing the repose angle of iron ore pellets obtained through the draw down test in a laboratory setup and then the elastic–plastic spring dashpot model was modified based on considering the individual parameters instead of relative parameters of two contact entities. Results showed that the modified model could produce higher repose angle. The modified model was used to calibrate DEM simulation of repose angle of iron ore pellets in a laboratory setup of the draw down test. Comparison of the calibrated DEM simulation and laboratory results showed 2° differences between the predicted and measured angle of repose. This difference was attributed to considering the particle shape effects by assuming a spherical shape for particles. Keywords: DEM, rolling friction,particle shape, repose angle

Jan 1, 2020

Sulphide minerals, such as pyrite and sphalerite, are leached by ferric sulphate. This reaction produces ferrous sulphate and other dissolved products. The ferrous sulphate is re-oxidized to ferric sulphate by bacteria. These reactions can be written as: [ ] However, in 1964 Silverman and Ehrlich proposed that this is not the only role that is played by bacteria. These researchers proposed that T. ferrooxidans enhances the rate of oxidation of pyrite above that achieved by chemical reaction with ferric sulphate at the same solution conditions. This enhancement in the rate of dissolution was proposed to occur by direct microbiological action, possibly by the extra cellular secretion of an enzymatic oxidant. Since the Silverman and Ehrlich proposal, different authors have made opposing claims concerning the action of T. ferrooxidanson pyrite. This ?direct mechanism? of bacterial dissolution of pyrite can be given by the following reaction: [ ]

Jan 1, 2000

By Noel A. Warner

Modern steelmaking is based on direct use of oxygen in high intensity batch reactors. A totally new approach is proposed in this paper, based on the view that pursuit of high intensity is unlikely to lead to successful coal-based continuous steelmaking. By substituting carbon dioxide and water vapor as the oxidants rather than using oxygen directly, the intensity is greatly reduced. Accordingly, subsurface formation of carbon monoxide bubbles can be avoided by careful manipulation of the three participating rate processes, gaseous diffusion, interfacial chemical kinetics and liquid phase mass transfer. Steelmaking can then be carried out without explosive ejection of molten droplets and the generation of micro-spray but rather in a controlled and fume less fashion. The vital component is the introduction of generic melt circulation technology. Three melt circulation loops in series are envisaged. Starting with a composite feed of iron ore fines, pulverized coal and lime flux, a metallized solid raft floating on molten iron is propelled out of the ironmaking loop onto the first of two downstream steelmaking loops. In the first, a liquid slag is formed, primary decarburization is undertaken not with oxygen but rather with CO2 and H2O and the melt is desulfurized. The semi-product stream enters the third melt circulation loop, where open-channel decarburization is effected along with dephosphorization to yield a low carbon steel product. Alternatively, the melt leaves the last loop to irrigate a packed tower countercurrent to argon at around 100 mbar to continuously produce ultra-low carbon (ULC) steel.

Jan 1, 2003

By M. B. Balachandra

A three-dimensional finite element analysis was performed of an instrumented section of a double-entry coal mine in order to provide a comparison between field measurements and existing analytic techniques. The BMINES computer code was used to perform the analysis. The sequence of excavation of the entries was considered, as well as the installation of rock bolts and cribbing during the mining cycle. The materials In the region under investigation were idealized into four rock types and coal. The rocks were assumed to be isotropically elastic, perfectly plastic. Coal was represented by an elastically anisotropic (transverse isotropy) and plastically isotropic model. A fracture yield criterion of the Coulomb form was used for all materials. The strength and stiffness of all materials were substantially reduced from available laboratory data to account for in-situ properties. Qualitative trends and stress distributions obtained from the calculation were found to be reasonable. However, computed displacements and closures were greatly exaggerated and an excessive degree of inelastic deformation was indicated in the coal, especially adjacent to the excavated faces. It was established that both these effects were the result of an excessive reduction in the strength and stiffness of the materials. The analysis underscores the need for three-dimensional calculations by identifying a number of important structural response parameters that would be either outside the scope of, or misrepresented by, two-dimensional analyses. The analysis also emphasizes the need for comprehensive and accurate measurement of material properties in order fully to exploit the power of the analytical techniques to generate reliable predictions.

Jan 1, 1976

By J. C. Engel

Recent innovations in mine safety include the use of mercury vapor lamps for mine vehicle illumination. Such lamps, however, extinguish whenever the line voltage at the machine momentarily sags or is interrupted. The lamps must then cool for several minutes before they will restart. By supplying reduced high frequency power to the lamps from an auxiliary source, it is possible to maintain ionization in the arc tubes preventing the lamps from extinguishing. Essentially an auxiliary high frequency supply, the keep alive system provides additional power to the lamps automatically whenever the lamps are in danger of dropping out. The system can also provide the operator with the ability to dim the lamps at will for periods of up to three minutes by simply interrupting the 60 Hz power to the conventional ballasts. Each unit, housed in a steel explosion proof enclosure with a volume of approximately 0.6 ft3, is capable of servicing up to six 175 watt H-39 mercury lamps and two 100 watt H-75 reflector flood lamps. A total of 16 units were produced for the USBM under this contract and its extension.

Jan 1, 1979

By J. R. Thoenen

In June 1929 the Bureau of Mines issued a 13-page Information Circular entitled "Mineral wool." This was one of the first publications to present to the public some technical aspects of the mineral-wool industry. Since that time several articles have appeared on the subject in the technical press as well as publications by State organizations. Inquiries for information on mineral wool have continued to be received by the Bureau of Mines in large numbers, and in 1935 it was decided, with the cooperation of the is industry, to make a field survey of the plants then producing and to collect therefrom technical data to be compiled in a paper for public distribution. As a first step, a brief questionnaire was mailed to the known producers asking if they would cooperate for publication. Favorable replies were received from of percent of the manufacturers, and the field work was started. As the study progressed and tie number of plants visited grew, it became more and more apparent that the industry had made rapid strides in technical operation and control of their product, as well as in increasing production during the mast decade.

Jan 1, 1938

By C. R. Copeland

Airborne dust emission standards are receiving growing attention. This trend is motivated by significant health studies that have shown adverse health effects due to exposure to dust. Currently, the air quality standards are not specific to particles in the nanoparticulate range (<1,000 nm). However, as our understanding of health related matters increases, it is very likely that nanoparticulate standards will be adopted. It was previously believed that typical comminution and material-handling practices could not result in airborne nanoparticulates. However, experimental studies using air monitoring and SEM have verified the presence of nanoparticulates in the air as a result of comminution and material handling. This means that emerging nanoparticulate air quality standards are a real possibility for industrial operations. With this emerging problem facing the minerals industry, effective suppression methods for nanoparticulates should be explored. Systematic studies have indicated that nanoparticulates from silica can be suppressed utilizing hygroscopic reagents such as calcium chloride. This reagent was as much as 93% more effective than water in suppressing silica nanoparticulates.

Jan 1, 2007

By R. J. Pine, J. S. Coggan

Distinct-element modelling has been used to study the mechanisms associated with observed deformation of the western face of the quarry. A complex failure mechanism involving distinct planar surfaces that was proposed for a slope failure in 1967 has been modelled and shown to be plausible. In addition, deep-seated flexural toppling may contribute to the slope instability. Modelling has confirmed the detrimental influence of a raised water-table on the stability of the slope and also indicates that the observed cyclic opening and closing of tension cracks may be attributed to seasonal rise and fall of the groundwater level

Apr 1, 1996

In November 1999 Waihi Gold Mining Company commissioned its new crushing and conveying plant used to transport both ore and waste from the Martha Mine to its ore processing plant and also its tailings dam construction area. To date, a record monthly throughput of 854 000 tonnes throughput has been achieved. This paper outlines the measures taken subsequent to the commissioning of the system to achieve greater than design throughput and to mitigate the environmental and safety issues associated with operating the system in the middle of a town.

Jan 1, 2001

By Adnan A. Malik, Tadashi Maejima, Jiro Kuwano

"ABSTRACTTheoretical approach to estimate the ultimate pile capacity gives a rough idea at the initial stage of design that later on strengthen by the execution of static pile load test at site. The static pile load test is the only best option for the estimation of ultimate capacity of various types of piles. There are various methods based on strength, serviceability, net deflection for end bearing, shaft adhesion, graphical and extrapolation approaches for the interpretation of pile load test data to calculate the ultimate capacity. In this paper an attempt is made to evaluate the best-fit method for the estimation of ultimate capacity of single helix screw pile. The pile load tests on model scale were performed on screw piles of different helix diameter. The purpose of adopting model scale of testing was to achieve a state at which settlement increases without further increase in vertical load. The ground was compacted with dry sand at denser state. It was observed from the test results that extrapolation methods such as Chin- Kondner and Decourt predict the load settlement curve of screw piles very well, however ultimate pile capacity was on higher side which may not be suitable for the strength of helix plate. Decourt approach to plot the pile load data showed clear indication of the deformation of helix due to strong subsurface condition. A modified approach in Decourt method is proposed for estimating the ultimate capacity of screw pile having deformed helix whereas reduction factor is suggested for Chin-Kondner method for the estimation of ultimate capacity of intact screw pile.INTRODUCTIONDeep foundations are used to avoid the soft ground at shallow depth that is not suitable for carrying the structural load. Different types of piles have been used to transfer the load to deeper stratum. The screw pile is one of the new piling method and its use is considerably increasing. It consists of a cylindrical steel shaft with one or more helices at various length of the shaft. The diameter of helices (Dw) is usually 2 – 2.5 times the shaft diameter (Ds). The pile is installed to the required depth through torque and pressure. The advantage of screw pile over other piling system is its quick installation mechanism, high end-bearing and uplift resistance, noise reduction and minimum use of man power."

Jan 1, 2014

By D. S. Burgess

About 100 tests of flammability were carried out with H2, CH4, and CO in mixtures with air using the Federal Bureau of Mines 12-ft-diameter spherical pressure vessel as an explosion test chamber. The LeChatelier approximation gave slightly conservative estimates of the limits of downward flame propagation (onset of significant pressure rise) using the following measured values for the individual gases, in percent: H2, 8.5; CH4, 5.25; CO, 13.0. No justification could be offered for using the LeChatelier law for upward flame propagation limits and indeed reported data suggest that calculated values would not be conservative. The observed upward limit for methane-air mixtures (4.85 pct) was less than the widely accepted lean limit for this fuel; those for lean hydrogen-air mixtures and carbon monoxide-air mixtures did not differ from the lowest accepted values. Diffusional effects on the propagation of single, binary, and ternary fuel mixtures are discussed.

Jan 1, 1982

Who Macraes Mining Company Limited is can be summed up by the following statements: +&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; We have been New Zealand&apos;s largest gold producer for seven years +&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; We have one of the lowest market capitalisation per reserve ounce of the gold producers in the &nbsp;Australian Gold Index +&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; We have a resource finding cost of less than NZ$l0 per ounce +&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; We have a large land bank with proven reserves +&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; We have an Operating Cash Margin of approximately NZ$200 per ounce +&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; We have reduced our Dry Milled Tonne Cost by 34% since 1992 &nbsp; Our Mission is to continually grow our gold business, through maximising cashflow and focusing on our value drivers being: +&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Increasing reserves +&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Increasing cash operating margins +&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Increasing production &nbsp; The real challenge is the reduction of operating costs and the optimisation of revenue, particularly in the current gold price environment. &nbsp; The Company has as at 31 December 1996 total mineral resources of 6.1 million ounces and reserves of 3.4 million ounces. This together with our current cash position of approximately NZ$15 million and strong hedging book of approximately 800,000 ounces places the Company on a sound financial footing whilst positioning itself to aggressively pursue its growth strategy when gold price and market conditions improve.

Jan 1, 1997

By Samuel Canchanya M.

El presente trabajo describe la mineralogía y génesis de los depósitos de cobre, plomo, plata y zinc de la mina Bella Unión ubicada en Hualcayoc, Cajamarca. En este sentido, la geología de dicho yacimiento presenta vetas como mantos. Así también se plantea la existencia de cuerpos estratoligados sin genéticos que se desarrollan en horizontes calcáreos albianos y coetáneos con los yacimientos en rocas volcánicas y dentro del lado oeste de los lados peruanos.

Nov 8, 1982

By Orlando Bernal

El presente texto aborda el aspecto termodinámico del sistema de lixiviación -en tanto predice los fenómenos que ocurren en el interior de la pila para luego continuar con el análisis del mecanismo cinético. La metodología aplicada en cuanto a los mecanismos de lixiviación, difiere de otros trabajos porque aquí se considera los tres mecanismos por separado (óxidos, sulfuros secundarios y primarios) basados en el análisis secuencial del cobre. Asímismo la cinética per se obedece las leyes de la termodinámica ergo, cuyo aspecto no puede ser ignorado en un análisis global. En este sentido, se presenta el modelo de desarrollo matemático como una herramienta óptima que controla y predice este proceso del lixiviación por medio de la simulación utilizando la ecuación de continuidad, la cual supone flujo tipo pistón de la fase líquida en el interior de la pila.

Sep 9, 2007

By S. J. Rodgers

This report presents the results of in-mine studies to determine the severity of dust sources in conventional mining operations. Three underground coal mines were surveyed using gravimetric samplers and GCA RAM-1 continuous dust monitors. Two additional mines were surveyed using only GCA RAM-1 monitors. Data on dust control methods were acquired during the survey, also. The results indicated that cutting/drilling and loading out were the dustiest operations during a conventional mining cycle. Roof bolting, shot firing and product transport were less severe dust sources.

Jan 1, 1983

The paper provides a brief review of a multivariate uniform conditioning and a localized multivariate uniform conditioning (LMUC) technique, and presents a production reconciliation case study based on a porphyry copper-gold deposit in Peru. The reconciliation study compares the longterm LMUC mineral resources model (typical of new mining projects, which are invariably based on drilling data on a relatively large grid) to the corresponding production blast-hole grade control model, as well as the final plant production.

Jan 1, 2014

By John C. Holtz

Information on the gaseous products from the detonation of explosives has been obtained in two ways. In the first, the atmosphere in mines is analyzed after blasting, aid in the second, the gases found after detonating an explosive in a testing apparatus are analyzed. The Bureau of Mines, in

Jan 1, 1940

By John C. Holtz

Information on the gaseous products from the detonation of explosives has been obtained in two ways. In the first, the atmosphere in nines is analyzed after blasting, aid in the second, the gases found after detonating an explosive in a testing apparatus are analyzed. The Bureau of Mines, in

Jan 1, 1940

By John Dunn, Matt Hawley, Kashif Butt, Nicholas Gura

"This paper presents the results of a static load testing program completed on helical pile foundations for the replacement of high voltage transmission line tower structures. The foundations were part of the Northeast Grid Reliability Project (NGRP) for the Public Service Electric & Gas Company (PSE&G) near Newark, New Jersey. Structure foundations “anchor bolts down” was a design build contract model with the superstructure as bid-build.The soil stratigraphy along the alignment generally consisted of fill over about 10 ft of organic deposits underlain by up to 260 ft of normally consolidated glacial lake clays and silts. Additional project challenges included working under/adjacent the existing live high voltage lines, narrow site access due to environmental permits, foundations in a tidally influenced area, and pile projections in the order of 10 feet to meet the 10 year flood level requirements.The helical piles were constructed of 12.75 inch diameter open ended pipe piles with 36 to 40 inch diameter helices. A total of seven static load tests (compression and tension) were completed on 60 ft and 90 ft long piles, using both welded and mechanical pile splices. To evaluate pile-soil setup in the sensitive fine grained soil and determine representative longer term installation torque factors (Kt) for the production piles, the static load tests were performed 7 to 49 days after pile installation.Helical piles were found to be the most cost effective foundation alternative for this project. The required length of helical piles was less than other alternatives for similar allowable axial capacity. Helical piles with mechanical splices were installed for the varying structure foundations including tangent and heavy deadend, to a deadend monopole. Installation of 448 production piles (34,320 linear ft) was completed in three months. The installation timeline was critical to meeting the semi-annual PSEG outage for switching the old and new structures. Helical piles employing a mechanical splice resulted in an efficient and effective foundation solution for the conditions encountered on the project."

Jan 1, 2017

By E. C. Perkins

As part of a program for developing methods of using domestic titanium deposits, the Bureau of Mines investigated methods for chlorinating titanium slags prepared from titaniferous minerals by electrosmelting. Titaniferous slags were made from ilmenites in the following deposits: Valley County, Idaho; Trail Ridge, Fla.; Aiken, S. C.; and Maclntyre, N. Y.; titaniferous magnetite from Iron Mountain, Wyo., were also evaluated. The tests were made in two chlorinators, a 4-inch and a 36-inch unit. Preliminary testing was done in a 40-millimeter bench-type unit. Chlorine gas was contacted with a loose mixture of titaniferous slag and carbon at a high temperature to form titanium tetrachloride. The moving-bed system used in this work involved a downward movement of feed countercurrent to the chlorine flow, and residues continuously removed from the bottom of the reactor. The performance characteristics of these slags depended on their composition, which varied widely according to the geographic source of the ore. The results showed that all but two of the slags could be chlorinated as effectively as rutile, converting 70 to 80 percent of the titanium to the tetra-, chloride. The two slags that proved difficult were made from New York ilmenite and Wyoming titaniferous magnetite. These slags contained enough magnesium to cause clinkering, which necessitated that the bed be prematurely withdrawn before more than 70 percent of it could react. The iron content of the slags did not interfere with operating the chlorinators. The data from the 4-inch and the 36-inch units were in agreement on the relative amenability of the slags to chlorination.

Jan 1, 1962