Search Documents

By Walker E. R

IN the early age of steel it was made hy what is known as the cementation proeess, in which wrought iron was embedded in charcoal and heated in a mufflc furnace to a tcmperature of approximately 1100° C. for varying lengths of time, the length of time depending upon the amount of carbon (or better known in thosedays as the degree of hardness) required in the finished product.By this process the resultant product obtained was not of uniform quality, and because of this uncertainty of quality Huntsman was induced, in the year 1740, to introduee what is known as the crucible process.This process consisted of cutting into small pieces the product of the cementation process, placing these pieces in a crucible, and melting them down with the aid of a eoke-fired furnace, after which the molten metal was cast into suitahly shaped ingots, from which could be hammered any desired shape.A section of crucible furnace is shown in Fig. 1. By this means a product, very uniform in character, was produced.The process is still in use, but, owing to its high operating cost, it is mostly eonfined to the production of very high-grade carhon and alloy steels. Its position to-day as a producer of these high-grade steels is, however, being very seriously challenged by the electric process.It was owing to the excessive cost of crucible steels and the need of producing a steel in commercial quantities and at a reasonable cost, that led Sir Henry Bessemer to introduce what is known as the Bessemer process.

Jan 1, 1930

By Hall J. S, Zuiderwyk M, Reid A. F

A prototype version of a computer controll- ed on-line scanning electron microscope image analyser, employing the real-time signals ob tamed by digital control of the electron beam has been used to obtain statistical quantificat lion of a wide range of mineral grain character istics, including composition, size distribut- ion, and degree of liberation. These propert lies have been determined for suites of whole particles of flotation concentrates, mounted without further preparation. The facility is also well adapted to the measurement of general Istereological parameters. The computer control software is based on an operating system which includes the device drivers and which is linked to FORTRAN programs [containing the procedural algorithms. The beam scanner provides a 4000 x 4000 point raster swept at a 10 Mhz rate in steps of 1 to 200 points and a set of up to 8 signal channels which respond to electron or energy dispersive X-ray signals to provide a digital attern.characterizing the sample composition. the beam is stepped at high speed until a part- 'cle or phase boundary is encountered; a longer well time is set if X-ray data is required. he digital scanner interrupts the computer

Jan 1, 1977

The Ramu chromite deposit occurs in the Marum Ophiolite complex and is the most economically attractive chrom-ite deposit in Papua New Guinea. Its lateritic nickel, chromite and cobalt potential has attracted several compan-ies to prospect the deposit.In the present work, the compositions of chromite in the Ramu lateritic deposit and coexisting olivine-chromite pairs in Marum Ophiolite dunite were analysed with the electron microprobe for Fe, Mg, Cr and Al. The results were used to determine the relationship between the cations in the tetrahedral and octahedral structures of the chromite. In addition, the Fe, Mg, Cr and Al cations of the coexisting olivine-chromite pairs were used to calculate the equilibrated temperatures of crystallisation of the chromite. The variation of Fe", Mg and Cr cation values of the chromite in relation to the calculated temperatures was studied by regression analysis.

Jan 1, 1994

The paper describes the studies conducted to date on the short term adsorption/desorption of gases in coal from the point of view of developing techniques to predict imminent outbursting conditions in coal mines. A number of different parameters such as'dP express, K' and AV 0/60 etc. which have been effectively used overseas were studied on samples of coal from Westcliff and Leichhardt Colliery. Results indicate that these do not seem to be valid indices for predicting an outbursting condition. Based upon desorption isotherms, a new index defined as "L" has been developed which shows promising results. This index is in a position to differentiate the changes in the structures of coal and its proness to outbursts. The "LZ value determinations and its usefulness opens a new field where it would be possible to determine outbursting conditions from existing drill cores obtained during exploration studies or from long holes drilled in advance from underground workings. The index is more or less independent of the time elapsed between the extraction of a sample and the conduct of the test. The test for "L" can be conducted'on site or in the laboratory. The test is simple, easy to carry out and the "L" value for a sample can be calculated in less than 20 minutes. It could be adapted as a routine test for monitoring outburst conditions in mines.

Jan 1, 1980

By Y S. M Tabatabaei, R Hosseini Tabata

Application of Acidithiobacillus ferrooxidans bacteria to flotation of Sarcheshmeh low-grade copper sulfide ore was studied. Sarcheshmeh low-grade ore contains pyrite, which causes some problems in the flotation of copper minerals. In this study, A ferrooxidans was used to change the surface chemistry of pyrite and copper sulfide ores and consequently, their flotation behaviour. In the presence of A ferrooxidans and xanthate as a collector, pyrite was depressed whereas chalcopyrite and other sulfide minerals were unaffected. In addition, the pulp pH remained unchanged. It was shown that the surface chemical properties of the bacteria could be manipulated successfully to achieve the desired effects in a flotation process. The results showed that the recovery of pyrite in the presence of the bio-depressant is 50 per cent lower than when no bacteria were present. At the same time the recovery of chalcopyrite remained unchanged.

Jan 1, 2004

By N Mangadoddy, P Jampana, S Diddi

The study of air-core dynamics in hydrocyclone operation is essential for predicting separation efficiency in mineral processing. Electrical resistance tomography (ERT) allows non-invasive measurements of hydrocyclone internal flow dynamics. Existing regularisation methods such as Gauss-Newton and TV norms rely on optimisation techniques which have very high computational cost for very fine meshes. In contrast, the monotonicity method has much lower computational cost as it does not solve such minimisation problems. In this paper, results from the monotonicity method, Gauss-Newton (GN) (Tikhonov) and Total-Variation (TV) norm-based minimisation methods for estimating the air-core diameter in hydrocyclones are compared. We study these methods on the laboratory hydrocyclone experimental two-phase flow data. The results obtained are validated against High-speed video (HSV) imaging and Computational Fluid Dynamics (CFD) results. The results on different mesh sizes, in particular for very fine meshes with the number of cells ranging from 30 000 to above 100 000 are also investigated. The data used in this study is obtained from ITS Z8000 ERT system. This system does not measure the voltages on the current carrying electrodes. Since these voltage values are required for the monotonicity method, we implement an interpolation method to compute them. The results show that the monotonicity method provides a closer approximation of the interface between air and the water phases.

Aug 24, 2022

After a short theoretical comparison of various typical large bell tops with the bell-less top for segregation and other ,ffects on the material flowing through the equipment proper, a comparative analysis between classical and the new burdening in the furnace is given, showing the theoretical effects of distribution and segregation on the horizontal pressure variations, temperature values and gas composition in the stack. Then some typical theoretical charging patterns of the bell-less top for wall and centre temperature adjusting, pressure drop corrections, dissymmetric local action for blow-in and scaffolding are described. Finally the available practical results on furnaces equipped with the bell-less top are compared with the theoretical statements made before and conclusions indicate that the new approach to burdening blast furnaces is a real improvement.

Jan 1, 1975

By Katsuyama K, Nag DK

Three aspects of rock mechanics, namely, in-situ stress estimation by acoustic emission (AE) method, strength of rock mass and role of chemicals to reduce the strength are covered. It is possible to detect the previously applied maximum stress by stressing a rock specimen to the point where there is a substantial increase in AE activity. This is known as Kaiser effect. From the AE signatures in the second and subsequent loadings, AE take-off point was identified more easily than in the first loading. In determining the compressive strength of rock mass, two factors have to be considered, namely, the size effect on the compressive strength of intact rock and the effect of discontinuities on the compressive strength of rock mass. Although a modified Bieniawski criterion gives best agreement with the triaxial test data, modifications have been suggested to Hoek-Brown criterion due to its popularity. It is possible to reduce the tensile strength of sandstone by saturating it with weak chemical solutions made with dodecyltrimethyl ammonium bromide, polyethylene oxide and aluminium chloride by up to 30%. In the case of compressive strength, there is no appreciable effect. The possible explanation is that the chemical solutions produce an effect on the strength of sandstone only when the failure mechanism is dominated by tensile mode.

Jan 1, 1998

This paper forms part of a series of papers relating to the Melbourne Underground Rail Loop and presented to the Fourth Australian Tunnelling Conference in Melbourne, March 1981. The Design of Electrical and Mechanical Services in Museum Station and adjacent Running Tunnels and their relation to Rail.wruy Operation through the Loop are described. The descriptions, while specific to Muscrio Station, are generally representative of those being provided at Parliament and Flagstaff Stations. The Museum Station comprises some 6500 square metres of platform and track area, 5000 square metres of booking hall concourse and entrances and 1200 square metres of offices and plant rooms. The Mechanical and Ilectrical Services for this complex are .imilar in many aspects to those of a large !.gr.hrise city building, but in general the i::;ign is directed more strongly towards :.arety, durability and reliability, and subject to many restraints imposed by L'mitations of space and accessability.

Jan 1, 1981

By Fourney W. L, Dick R. D

Tests were conducted in plexiglass and Rockite models to determine if crater blasting could be improved by changes in charge geometry or by alterations to the borehole. Circumferential grooves were placed at various locations in the borehole in an attempt to control the initiation site of the crater. Grooves located at or above the top of the cylindrical charge had no effect on the resulting crater. Grooves placed too low in the borehole were successful in controlling the initiation site but the growth of the fracture system was not sufficient to reach the upper surface. Grooves located at a height of two thirds of the charge length were quite successful in that resulting craters were bigger by at least a factor of six than the normal crater. Testing was conducted in Rockite models to investigate charge geometry. Spherical charges in ungrooved boreholes resulted in crater sizes that were three times larger than those caused by cylindrical charges.

Jan 1, 1990

By Jankola W. A, Delong O. J

Historically, the silica content of zinc concentrates treated at Cominco's Trail Operations has been low. Silica in the roaster calcine seldom exceeded 1.5 per cent because of the low silica content of concentrate from Cominco's Pine Point mine. With the shutdown of Pine Point, alternate sources of concentrate were required and it was anticipated that calcines containing greater than two per cent silica (with excursions above three per cent) would have to be treated. Previous experience indicated that the existing leaching circuit could not tolerate such high levels. Therefore, a research program was undertaken to identify the key factors affecting silica precipitation; to compare different process alternatives; and to make recommendations for modifications to the existing plant. A project to modify and upgrade the leaching circuit has now been completed. Calcines with higher silica contents are successfully treated, but the upper limit of the circuit is unknown. The results of the research work will be discussed and the new leaching plant will be described. Recent operating results will also be presented.

Jan 1, 1993

By Scales PJ

Fatigue is the primary cause of failure of structural and mechanical components subject to dynamic loading. Recognition of this basic fact and the development of appropriate techniques and details are important in the design and repair of off highway trucks (OHTs). The frames and appendages of OHTs and other mobile plant used in the Pilbara are subject to tough operating conditions. Any fatigue-prone details quickly show up and become a maintenance liability of considerable concern. Much of this equipment is approaching the limit of its fatigue life and maintenance managers face decisions on whether to repair or replace. Even new equipment often contains some poor details which suffer distress soon after commissioning. In those cases a repair is required which will reinstate the detail to its original intended design life. Repair details must be practical and cost effective. They must also be tailored to the capability and expertise available in the field or in local manufacturers' establishments. This is particularly important where original equipment was manufactured overseas and long delivery times are involved. Lessons are drawn from components which have failed, using the evidence constructively, to provide an upgraded part or an improved substitute. With the experience now available it is relatively easy to extrapolate to cover new problem areas. This paper describes specialised techniques of mechanical fastening and detailing for low fatigue susceptibility, built up over many years of experience with OHTs and other mining plant and equipment in the Pilbara.

Jan 1, 1982

Grade control aims to deliver quality tonnes to the mill via accurate definition of ore and waste. It comprises data collection and interpretation; local reserve estimation; supervision of development and mining; and stockpile management. The foundation of all grade control programs should be that of high quality sampling supported by geology. The requirement for quality grade control samples has long been recognised, where they should be representative, unbiased, safe and operationally timely. Underground sampling methods include chip and channel samples; grab samples; and drill-based samples. To achieve quality samples, collection techniques employed should minimise delimitation, extraction and preparation errors. Grade control staff should be well-trained and motivated, and mining staff should understand the need for grade control. This paper reviews grade control sampling methods and presents recommendations for best practice and minimisation of sampling errors.

Mar 1, 2010

By Baafi EY

Open cut mining in Australia is facing the greatest challenge in its history in attempting to compete not only with other operations internationally, but also with underground operations domestically. Most flat dip and shallow depth surface-mineable coal reserves have been depleted during the last two decades and new open cut operations must extract deeper coal deposits. As open cut coal mines move into deeper areas and the stripping ratios increase, the relative cost of overburden removal also increases. It therefore becomes even more important to design the mine around the optimum overburden removal scheme. The deeper mines are usually multi-seam operations with a more complex geology and with more geotechnical and hydrological problems. Deeper mines are subjected to greater problems requiring more detailed mine planning and design, such as selection of the optimum mining method and pit layout. In planning and design of such operations, the number of alternative methods which need to be considered is consequently greater.Dragline productivity and its stripping capabilities are directly affected by the selection of digging method, strip layout and pit geometry. Every mine has a unique combination of geological conditions. The operating methods that work well at one mine may not necessarily work at another site. Selection of an optimal stripping method, strip layout and pit geometry for a given dragline must be considered with respect to the geological conditions of the mine. With increasing geological complexity of Australian strip mines, it is becoming more important to use sophisticated techniques such as computerised mine planning methods to assist in optimising dragline operations.

Jan 1, 1998

By G Chitombo, M Ruest

In surface mining, studies of the kinematics of blasted rocks using high speed film/video image analysis have allowed the estimation of the starting time, direction and magnitude of visible movement of fixed sections of the free face. Horizontal displacement versus time plots from discrete targets at the face generally report changes in slope over very small time intervals. These changes indicate step increases in velocity due to the action of explosive gases. In practice, the onset of rock mass movement, different to localised spalling, has been associated with a response time which exceeds the combined times of detonation, propagation and reflection of stress waves. This time is referred to as minimum response or burden movement time. As an engineering index, burden movement time has been used to provide guidelines for the selection of inter-hole and inter-row delay sequences in production blasting. With respect to improving breakage and fragmentation, it has been demonstrated that the delay interval between adjacent explosive charges should be less than the expected burden movement time. Similarly to reduce confinement between rows, delay intervals should exceed the expected burden movement time. The Hybrid Stress Blasting Model (HSBM) is a modelling framework that dynamically links an ideal and non-ideal explosives detonation code to a geomechanical rock model. This blast simulation tool is aimed at analysing the role played by different explosive formulations in fragmenting and/or damaging various rock types under different degrees of confinement. In the current framework, the rock behaviour under extremely high pressures and loading rates is calibrated from shock tests and the role of the explosive in fracture growth is accounted for and assumes a compressible fluid flowing through the explicit fracture network. The model is being developed as part of an international collaborative research project funded by a consortium of companies comprised of explosive and equipment suppliers and major mining houses. As part of the development and validation of the HSBM project, data from literature addressing the kinematics of the rock mass (ie burden displacement, face velocities and response times) has been collated and used to evaluate the current version of the code. A series of numerical experiments have been conducted with the view to: evaluate the response of the rock mass to changes in burden distance given by the impact of both stress waves and radial gas flow pressure;compare the modelling outcomes in terms of displacement, response time and face velocities to documented field observations; andcompare stress induced and stress/gas induced modes in terms of burden displacement outcomes. Results from these experiments have shown that in its current form the model is able to capture the trends observed and measured in practice. This is with respect to the simulation of burden displacement, response time and average face velocities for different geometries and charging conditions. The experiments have served as consistency checks which form part of an ongoing and comprehensive evaluation and validation of the HSBM code also aimed at addressing some of its current limitations.

Jan 1, 2007

Like almost any other 19th century mining area, the West Coast saw its 20th century scrapping era when machinery which had been installed in seemingly inaccessible places was somehow dragged out again. Fortunately there were some spots so remote that they defied even the most zealous of these pioneering recyclers. One of these was Big River, a mining locality in a rugged landscape straddling the headwaters of the Grey and Inangahua rivers. As a result there remains an internationally important collection of mining equipment including a poppet head, two steam winding engines, a pair of boilers, part of an aerial cableway with its loading system, and remnants of a stamp battery along with its associated gold smelter, cyanide tanks and zinc boxes. There are also assorted building remains associated with 60 years of mining and settlement. Since their abandonment in 1942, these relics have all somehow survived a further half century in a far from favourable climate with two or three metres of rain a year, frequent snowfalls and hot summer temperatures. The rate of decay during the past few years has been alarming.

Jan 1, 1996

By Brown GA

Results are presented which demonstrate the feasibility of employing electrolytic membrane technology to process leach liquors derived from alkaline pressure leaching of scheelite concentrates and to recover and recyle sodium carbonate. Thus the problem of disposal of sodium sulphate is avoided. In a further application of the technique sodium tungstate is converted to tungstic acid which can be further processed by three possible routes to crystalline or amorphous tungstic acid or tungsten powder. In each route sodium hydroxide is produced which on carbonation can be recycled as soda ash to the pressure leach stage. Further testwork is required to determine long term operational conditions in the membrane cell and to confirm the effect and deportment of impurities on products. The process has been patented.

Jan 1, 1986

Traditionally, the Lead Lode at Broken Hill has been represented on presentation plans, cross sections and diagrams in scientific papers as a solid black mass, around which the more 'interesting' and 'structurally useful', wall rocks appear to wrap. Structural analysis of the Broken Hill orebodies has usually turned to these wall rocks to determine the structural history of the mineralisation.This tendency to represent the orebody as a massive single entity is incorrect and the aim of this paper is to illustrate that sulphide orebodies (in this case Lead Lode), are a dynamic part of the mine stratigraphy. They can preserve a great deal of useful structural information that can be recorded with detailed internal mapping.Three main categories of ore type are recognised in Lead Lode; Stratiform ores, Mobilised ores and Metasomatically altered ore. The ore types in these categories occupy or have formed in distinct structural and stratigraphic positions and have clearly recognisable inter-relationships.

Jan 1, 1993

By Jensen W. S

The Mount Morgan ore-body is intersected by dykes to such an extent that it presents peculiarly difficult problems in extracting ore. These are shown on Plates Nos. LXVII. and LXVIII. Besides ,these dykes there are innumerable "heads," which alsoare a source of danger. Falls of ore occurred in the end of the year 1908, resulting in serious loss of life to miners employed. It was decided, after an exhaustive inquiry, to change the entire system of mining from the" flat backed stope system" to the" square set sectional system ," the latter being more flexible and allowing bad ground to be cut out from a safe position; but it became evident that, whatever system was adopted, there would be more or less danger unless all the dykesand heads known were picked up, and their continuation plotted on a special set of plans on which the general scheme of stoping could be plotted from time to time as work progressed. It is worth while pointing out that, in every other branch of engineering, it is usual to design the work, and that only in mining engineering has it been common to do the work first and plot it down afterwards.The term "sectional analysis" is familiar in most branches of engineering design, and as applied in this paper to mining, may not bear the same meaning, but the general purpose is analagous, and there is no other term used.

Jan 1, 1911

By Chitombo G. P, Thompson A. G

Excavation engineering involves three key design processes; excavation design, blast design and reinforcement design. An excavation engineering methodology is proposed in an attempt to promote integration and simultaneous consideration of these three design processes. This methodology requires research and development of, inter alia, a universal rock mass classification system and a universal data display system. Simple examples are used to explain and illustrate the concepts central to these components in the three design processes.

Jan 1, 1995