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By R. F. Stewart

A sedimentation method involving the use of the Palo-Travis apparatus was found satisfactory for rapid determination of the size distribution of coal particles ranging from 10 microns in diameter to those passing an 840-micron opening (20-mesh sieve), The method is most useful for comparing the size distributions of samples of pulverized coal where the actual size of the particles is not required and is applicable to sieve and subsieve sizes of a wide variety of coals and chars that can be wetted and are heavier than water. An analysis, including all calculations, can be completed in 1/2 to 10 hours, depending on the time required for the finely divided coal to settle. A typical analysis requires about an hour, making this a rapid, precise method for routine size-distribution analysis of powdered coals. When used with coal particles smaller than 400 microns, the method is precise within 15 microns for wide variations in test conditions and within 5 microns for identical test conditions. The precision decreases as particle size increases, becoming unsatisfactory for particles larger than 400 microns (40-mesh). For precision within 15 microns, the samples must be equal in weight. Greater precision is obtained with 4-gram samples, but samples as small as l gram may be used.

Jan 1, 1961

By Carlos Maurício F. Vieira, Gabriel Oliveira Glória, Maycon Sidney Gomes de Camargo, Sergio Neves Monteiro, Fábio da Costa Garcia Filho, Maria Carolina Andrade Teixeira, Frederico M. Margem

The society is increasingly the concern about the ambiental impacts, and demand for eco-friendly materials. The composites reinforced with synthetic fibers are been replaced by composites reinforced with natural fibers because of the environmental advantages. Besides the environmental advantages, those fibers have economical and properties advantages, like the low density and cost. Composites with up to 30%of PALF fibers were tested. The analyzed parameters were the loss modulus, the storage modulus and the delta tangent. The test was conducted in the temperature interval from 25 to 195 °C in a DMA equipment operating at 1 Hz of frequency under a nitrogen flow. The results showed that the incorporation of continuous and aligned PALF fibers tends to increase the viscoelastic stiffness of the epoxy matrix. Contrasting this, minor changes occurred in both the glass transition temperature and the damping capacity of the structure as measured by the tan delta peaks.

Mar 1, 2018

By D. W. Alexander

Mine fires, explosions, spontaneous heating and inundations are among the leading causes of catastrophes (unplanned, temporary sealing and recovery of major mines). Many reports are available that detail company efforts to re-establish mining operations and agency efforts to regulate away the causes, but the associated costs are rarely included. The increasing scale of coal operations concentrates earning potential and the financial risk of business interruption in fewer locations. Underground coal mine catastrophes are low probability, high loss events that happen nearly every year. This paper will present an evaluation of coal mine catastrophes from case studies.

Jan 1, 2003

By Richard J. Mainiero, James Q. Wheeler, Lewis H. Kopera, Yael Miron, Solin S. W Kwak

The research reported here was part of an effort to evaluate the safety of a process to recover TNT from MK-9 depth bombs by the autoclave meltout process. In this process the depth bombs are heated to 121oC so that the TNT will melt and run into a vat. Unfortunately, asphalt lining the inside surface of the bomb also melts and flows out with the TNT. Prior to this study, it was not known what effect the asphalt contamination and the higher than normal process temperatures (121oC) would have on the sensitivity of the TNT.

Jan 1, 1996

By J. W. Spretnak, R. Speiser, A. M. Adair

THERE are sufficient arguments and evidence to indicate that boron should be adsorbed to existing austenite grain boundaries during the austen-itizing treatment. Accordingly, it is possible that boron contributes to the hardenability of heat-treatable steels by the reduction of the interf acial energy of austenite grain boundaries, at which sites are nucleated heterogeneously the decomposition products of austenite. Such a reduction in interfacial energy would reduce the total energy that can be borrowed in these heterogeneous nudeation processes and thus retard the initiation of transformation. This investigation was undertaken in an attempt to determine the effect of boron on this interfacial

Jan 1, 1956

By Horace C. Knerr

It has been shown that the resistance to corrosion of duralumin sheet is greatly influenced by the quenching medium used in heat treatment, or, more specifically, by the rate of cooling during quenching. The severity of corrosive attack after exposure to salt-water spray increases in .the following order: The tensile strength, yield point and elongation are only slightly affected by the quenching medium, as shown in Table 1. Tensile test requirements: yield stress, 25,000 lb. per sq. in. minimum; ultimate stress, 55,000 lb. per sq. in. minimum; elongation in 2 in., 18 per cent. minimum.

Jan 1, 1931

By A. J. Rigby

Current practices employing porous plugs to inject nitrogen into molten copper during primary smelting are described. Nitrogen stirring increases heat transfer to the bath, eliminates temperature stratifications, and improves efficiency during the steps of desulfurization and deoxidation. The opportunity to use porous plugs as the means to introduce reducing gases to deoxidize copper is also discussed. Previously reported laboratory results using porous plugs, which point to very high utilization efficiencies of hydrogen when used as the reducing gas, are again reviewed. Advances in the design of the porous plug, and the introduction of a system enabling external replacement of plugs is also discussed.

Jan 1, 1999

By M. K. Matthews

The use of backfill has important environmental control implications which, although frequently overlooked, can be both beneficial and problematical. Where backfill is widely used, the reduction in stope heat load and improved air utilization influence the overall mine ventilation and refrigeration requirements significantly. A programme of work examining in detail all the environmental consequences of backfilling is currently underway at the Environmental Engineering Laboratory of the Research Organization of the Chamber of Mines. This paper gives an overview of the work and presents some findings. In so doing, the environmental implications to be considered when backfilling are highlighted.

Jan 1, 1988

The Olympic Dam Mine is a large, mechanised, underground operation currently producing 2.2 million tonnes-per-year of copper/uranium/gold ore. The mine is accessed via one shaft and one service decline. An additional 13 raise bored ventilation shafts have been completed to-date.Ventilation requirements are stringent in order to provide adequate dilution and removal of diesel fumes, radon gas/daughters and heat generated from both engines and wall rock.Due to the nature of the orebodies, the mine workings will continue to expand laterally necessitating the addition of at least one major surface raise every year.

Jan 1, 1992

By Hayes P. C

In commercial mineral processing operations it has been found that the conditions in the drier have a considerable effect on the subsequent electrostatic separation of nttile and zircon. Laboratory scale studies simulating these heat treatment processes have shown that the electrical conductivity of nitile varies markedly with treatment temperature, time and gas composition. The zircon on the other hand is unaffected. By increasing the electrical conductivity of the rutile, significant increases in separation efficiency can be achieved. Electron microscope investigations have shown the increase in electrical conductivity to be associated with the production of planar defects in the crystal lattice.

Jan 1, 1991

By D. C. Jillson

BRIDGMAN1,2 melted metals in a graphite or hard glass tube and lowered the tube through a furnace to make it cool from one end only. Because of the difficulty of eliminating all vibration of the mold, others have raised the furnace instead. Neither way seems as desirable as a setup with no motion of either the mold or the furnace. A furnace in which both the shape and the slope of the temperature gradient could be controlled and varied over a wide range and in which such a gradient could be moved from one end of the furnace to the other, freezing the specimen from one end to the other, at any desired rate, all by means of isolated external control, seemed to offer definite advantages. In addition to eliminating the possibility of vibration due to moving parts, it might also give better control over the direction and rate of heat flow. Such an apparatus was assembled and is shown schematically in fig. 1. Equipment Furnace: A clay-carborundum tube of 3 1/2 in. ID with a % in. wall thickness was used as the core. This had a main winding of No. 12 B.&S. gauge Nichrome V with some compensation for heat loss at the ends. Taps to this winding were made at points 12 in. from each end. Fig. 2 shows details of this winding and of the two end windings. Each end winding was wound over Micanite over the main winding. No. 15 B.&S. gauge Nichrome V was used for these, and again taps were supplied at two inter-mediat,e points on each. The tube was supported in an 18 in. OD black iron shell with brick insulation. The input to each of the windings was regulated by means of a variable transformer. Temperature Regulation: A chromel-alumel thermocouple located near the furnace wall in the center of the furnace was connected with a Celec-tray controller, type PIC, 300" to 900°C range, which opened and closed a shunt across an external variable resistance in the main winding circuit. An "anticipatory response" device also was incorporated to minimize the cyclic effect of the control mechanism. Eleven survey couples in a common pyrex glass protection tube were located near the furnace wall and spaced 2 in. apart. The couple leads went to a common reference junction box where they were connected to copper leads from a selector switch which, in turn, was connected to a type K potentio-meter. This arrangement permitted rapid temperature surveys. The knob on the controller dial was replaced with a threaded brass spool turned at a controlled rate by a thin iron wire one end of which was attached to a gear train and the other to a small weight heavy enough to prevent slipping of the wire on the spool. The gear train, driven by a 1-rpm Telechron motor, contained a series of different sized interchangeable gears and threaded drums permitting a range of travel speeds from 0.10 in. per hr up to a hypo-

Jan 1, 1951

By Mohini Patel, Jahnavi Parmar, Pranav R. T Peddinti

Expansive clays pose a variety of geotechnical problems. Although the admixture stabilization is proven to address their problematic swelling and shrinkage characteristics, the influence of unsaturated condition on the engineering performance of these soils needs further research attention. In addition, highly saline soils with high organic content would further alter their performance. A similar soil stratum was encountered at the Gulf of Cambay, Bhavnagar district, India. High salinity in the in-situ expansive soil of basaltic origin and the prevailing unsaturated condition, enforces the engineers to look out for possible soil treatment methods. In this regard, the present work attempts to analyze the unsaturated behaviour of this soil when fly ash is used as an admixture. A comparative study for stabilized and unstabilized mixes is performed in terms of their unconfined compressive strength, electrical conductivity, swell characteristics and California Bearing Ratio.

May 1, 2022

By Robert Peretti, Antonio Zucca, Andrea Manni, Silvia Serranti, Paolo Massacci, Marcello Ghiani

"This research study aims to identify the best way of processing colemanite concentrates, which is sometimes characterised by a high content of As sulphides, finely disseminated in the matrix of the boron mineral.Scanning Electron Microscopy analyses have been carried out to identify all the mineralogical constituents and to evaluate their distribution, frequency and mutual relationships.Colemanite concentrates are mainly used by chemical plants producing boric acid and gypsum. A high As content is unacceptable for further use of tailings coming from the leaching process and is very dangerous if the tailings are released into the environment.Grinding tests were conducted under dry and wet conditions in order to assess how As sulphide minerals are released from colemanite minerals.Some of the difficulties involved in obtaining selective liberation of As sulphides from colemanite minerals were overcome, although a certain decrease in As grade in the higher size classes was registered.All comminution products have been analysed by SEM, monitoring the degree of liberation of the mineralogical constituents.Flotation tests have been carried out, following different comminution flow sheets and adopting different modulating conditions in order to evaluate the influence of the following parameters:- collector concentration versus contaminants concentration (As minerals) in the froths;- kind and quantity of the frothing agent to maximise mineral recovery in the froths;- kind and quantity of the modulating agents to maximise the selectivity of the process;- conditioning modalities in order to obtain a suitable dispersion of fines and avoid segregation of Asbearing particles together with colemanite ones;- solid/liquid ratio of the pulp to minimise the water flow into the plant.Information obtained from SEM analysis has been adopted to evaluate segregation phenomena in pulp and in flotation products."

Jan 1, 2003

By I. S. Solet

This study, of the liquidus temperatures and densities of molten alloys of zinc and aluminum was made as part of a broader investigation on refining of scrap aluminum. One of the methods of refining involves the separation of liquid and solid phases by gravity segregation and by filtration. More accurate data were required on the liquidus temperatures and the densities of molten' mixtures of the metals than were available in the technical literature. New data on the liquidus curve were obtained by thermal analysis. The new temperatures are, for the most part) somewhat higher than those reported previously by other investigators. The density of molten mixtures of zinc and aluminum were found to be less than would be calculated by assuming that the two metals occupy the same respective molal volumes in solution as they do as pure metals.

Jan 1, 1949

By G. V. Cullen, N. G. Siviour

It has previously been reported that metal loadings of up to 6.8 m. eq/g. of dry coal can be obtained by contacting brown coal or lignite with ammoniacal solutions of ammine forming metals. Application of equilibrium expressions to further experimental results indicates that the extraction is by ion exchange, that the exchange is divalent-univalent for Zn, Cd and Ni, but is mainly univalent-univalent for Cu, and that to obtain reasonably uniform values for the equilibrium constants correction formulae must be applied to compensate for multiple functionality of the coal and its pH dependence in ion exchange. The results are shown to be consistent with the hypothesis that metal ammine complex cations are exchanged for protons derived from carboxyl and/or phenolic hydroxyl groups in the coal.

Jan 1, 1981

Most text books on rock blasting claim that the relationship between burden and borehole diameter is linear. The statistical calculation presented here with real values from one hundred open pit and underground mines indicates that the relationship is exponential. For underground mines the burdens are consistently lower than those for open pit mines because of higher ore densities, greater confinement in blasting, and finally greater demand for well fragmented rock. The results shown in this paper are recommended to be considered in basic teaching of rock blasting technique. The formulas can be used for a first rough estimation of practical burden and spacing. The formulas do not however give any information about the fragmentation. For that purpose it is necessary to use other formulas not described in this paper.

Jan 1, 1990

By Marcos Figueiredo Nicolau

O fluxo de produção da VSB contempla um alto-forno a carvão vegetal e uma aciaria elétrica. Para melhor sincronizar a programação do alto-forno (AF) e a do forno elétrico (FEA) é importante ter um conhecimento prévio de quais corridas do FEA usarão gusa líquido. Foi desenvolvido este projeto visando auxiliar na tomada de decisões da programação do AF e do FEA, a partir de uma simulação da logística de movimentação das panelas de gusa em cenários pré-determinados. Dentre as respostas que podem ser obtidas por essa contribuição técnica destacam-se: o número mínimo de panelas que devem ser utilizadas no circuito, quantas e quais corridas do forno elétrico serão atendidas com gusa líquido e a contribuição de cada meio de transferência de calor para a perda térmica total.

Aug 1, 2018

By ELIHU THOMSON

IN 1877, Professor Thomson delivered at the Franklin Institute, [Philadelphia, five lectures on electricity. The object of the lectures and the demonstrations, which were numerous and many of them original even to the employment of special apparatus constructed by the lecturer, was to show clearly that electricity, of whatever name, was the same., differing only in tension (as it was termed) and in the current flowing, or quantity (the old term), in steadiness or in wave-like character. In those days, the textbooks divided the subject into statical and dynamic electricity, with sub-divisions such as frictional electricity, voltaic electricity, magneto electricity, electromagnetism, thermo electricity, and animal electricity. The well-known Ruhmkorff coil,' or spark coil as it is now called (as when used for the ignition of automobiles), was employed to step, up a battery current to a high-tension discharge which would charge condensers, such as Leyden jars.

Jan 1, 1921

By J. W. Bingay

The expansion of the mining industry, with other industries, of course, is dependent upon a supply of fresh capital from year to year. Mining is a speculative form of investment, though there is a wide range of risk as between indiudual undertakings. All of the leading financial writers, nowadays, agree that expansion is being seriously interfered with by the unprecedented load of taxation Canadians are carrying. Individuals have less for investment and corporations are obliged to defer necessary expenditures in order that the demands of the taxing authorities may be met. Naturally, speculative investments such as mining exploration suffer first. Undoubtedly, a great deal of cash raised by taxes, if left in the hands of individuals and corporations for investment and expansion, would have been far more beneficially used and would have developed the country more than any use made of it by the government, in the way of bonusing new industries, or the undertaking of large schemes of development. Government undertakings of this nature are often entered into without a proper knowledge of cost and probable return. Expert expenditure of the same sums by business men or corporations undoubtedly would generally produce more prosperity for the country as a whole. The absolute necessity for lower taxation is being increasingly known to the public at large, and eventually it is hoped that our governments will see the economic impossibility of continuing the present rate of expenditure. The successful Finance Minister of the near future will not be the one who can borrow the most money.

Jan 1, 1924

By R Cooksey

The Globe-Progress Mine is an open pit gold mine that is part of the larger Reefton Goldfields deposit located on the West Coast of New Zealand. The regional geology comprises a series of north to south oriented fold structures that have undergone post-deformation mineralisation. The structural geology within the mine itself is more complex, with major shears hosting numerous high-grade mineralised quartz shoots and splays that have been historically mined.The selective mining of ore within the pit is challenging due to the orientations of the hanging wall and footwall areas of the main Globe shear zone, the lithologies of these areas which range from highly brecciated and sheared material to competent mineralised host rock, and in the hazards presented by the numerous old historic underground workings. The coordination of drilling, modelling and excavation of the ore requires careful planning to maximise recovery whilst operating with the pit design boundaries.Grade control packages are custom designed to reflect the orientation of the footwall and hanging wall mineralisation. The shear material in the footwall zone dips between 60° and 70° and requires angled drilling whereas the footwall mineralisation is contained in shallow dipping quartz veins sub parallel to bedding and can be vertically drilled to best intercept the mineralisation. Ore excavation is directed so that the contact between the footwall and hanging wall is mined in the correct direction so that any non-visual ore contacts can be safely mined and that the ore-waste dilution is reduced.The ongoing grade control and selective mining of the Globe Progress deposit continues to deliver high grade ore for processing by ensuring that waste and dilution of ore is reduced and that recovery is maximised.

Aug 22, 2011