Search Documents

By Beattie T

For many years explosive sensitized explosives were assessed using the ballistic mortar. The standard test used lOg of explo- sive initiated with a detonator. Over the past 30 years many non- explosive sensitized explosives and blasting agents have been developed. Most of these new explosives and blasting agents cannot be tested in the ballistic mortar as they are not initiated by a detonator. It is also known that all explosives have a criti- cal diameter. When the cartridge diameter is less than the criti- cal diameter a stable detonation cannot be produced and the explosive fails to propagate. For many blasting agents the criti- cal diameters are greater than 50mm and such large diameters cannot be tested in the ballistic mortar. The underwater test allows explosives to be tested in diameters greater than the critical diameter and to be adequately initiated with suitable boosters. The effects of the explosive on the water are easy to measure and the test provides a safe, convenient and reproducible means of assessing explosive performance. The reaction products are allowed to expand to a low final pressure. The underwater test can therefore be used to give a measure of the total expansion work of explosives. The detonation of an explosive induces a shock wave in the surrounding water. The profile of the shock wave can be meas- ured 3-6m from the charge and the energy in the shock wave cal- culated. Measurements over a range of distances show that the shock wave is attenuated as it travels through the water and the attenuation is different for each explosive. This makes it difficult to estimate the energy dissipated in the water between the charge and a single gauge. The reaction products continue to expand and displace water. The bubble continues to expand until the kinetic energy of the water is zero. The gas pressure in the bubble is now lower than the hydrostatic pressure and the bubble radius is a maximum. The higher external hyrdostatic pressure causes the bubble to implode. The bubble energy is the work done displacing the maxi- mum bubble volume against the hydrostatic pressure and can befound from the bubble period. It is not always easy to find a large enough pond for the bubble to expand undisturbed by the water surface and the containing boundaries. This makes it difficult to determine the bubble energy accurately in shallow Ponds.

Jan 1, 1988

To obtain the best economic results in treating the comparatively high-grade ore of the Kalgurli Mine a good roast is essential, and the effort of this paper will be to briefly describe the plant and the conditions prevailing in roasting, which, on an output of about 360 tons daily, subsequently enable an average extraction of slightly over 94% of the gold to be maintained.The percentage of sulphur in the ore varies between 2'5 and 3'5, the lower figure existing when treating oxidized ore. The average gold value is 13 dwt; this occurs chiefly as sylvanite, containing .a lower percentage of silver than is usually present in that mineral. One ore body in the mine contains hessite (Ag2Te) in considerable quantity, associated with gold telluride, and when ore from this stope is being treated the silver contents rise to as high as 20 dwt, but the usual amount is about 9 dwt. per ton, of which only a small proportion is extracted. Other metallic minerals, in addition to pyrite, occurring more or less commonly, are arsenopyrite, magnetite, chalcopyrite, and the tellurides calaverite (AuTez)and coloradoite HgzTe3). A small proportion only of the value occurs as free gold.

Jan 1, 1911

By J Araya, O Leiva

The mine evaluation process, composed of the designing, planning and valuation of a mine project, is, among other variables, based on an estimated orebody model. However, as the information from the drill holes is limited, it is impossible to know with certainty the mineral content in each block within the estimated block model. Consequently, uncertainty about the value of metal grades, or other geological attributes, arises because of the lack of information at unsampled locations. This is one of the reasons why, in any mine operation, there will always exist a divergence between estimated and real values. Cut-off grade optimisation is the process used to determine the operating mining strategy (long-term production scheduling) that will maximise the total profit value (normally referred as the net present value (NPV)) of a mine operation. This is done by defining a dynamic cut-off grade policy which is constrained by the production capacity of the mining, mill and refining.Real options is a type of contract, written on real assets such as mining, oil and other natural resource industries, that gives you the right but not the obligation to exercise the contract. It is based on operational and managerial flexibility, which allow mine decision makers to react to either good or bad operational and economic events in the future. But, what do geostatistics and cut-off grade optimisation have to do with the application of real options in a mine project evaluation process? The objective of this paper is to answer the previous question by showing how geostatistics combined with cut-off grade optimisation are key tools for corporate/managerial decision makers, which allow them not only to analyse the resource/reserves of their projects, but also to generate operational strategies that can maximise project value by minimising the downside risk due to ore tonnes and grade uncertainties, while achieving operational and physical constraints such as mining and processing capacities. A real copper grade open pit mine project is used as a case study.

Sep 26, 2011

By Hood M

Rock cutting excavation technologies and particularly continuous excavation technologies, can offer benefits in the areas of reduced costs, higher revenue and increased safety in a variety of mining situations. Non-explosive rock excavation technologies for example, can deliver significant benefits in the areas of dilution and improved ground support (no overbreak). This paper is an attempt to focus on the development and future of alternative rock breaking technologies and to provide some insights as to why and how we should proceed in this direction. The market size for underground hard rock excavation technologies is examined. A short review of the evolution of various rock excavation technologies in terms of cost and production rate is given and a summary of the state-of-the-art technology is presented. Mechanical excavation technologies (TBM) have very high production rates compared to D&B and the gap is widening, however, they have not been successfully applied to mining applications. Operating costs for mechanical and D&B systems have been dropping over time, however, D&B costs are the lowest. Given the current state of knowledge it appears that with regard to hard rock underground metalliferous mining that R&D efforts should be focussed in the following areas - disc cutter tool development (materials and design; operation; presentation to the rock surface), hybrid cutting systems (consisting of water jets and disc cutters) and development of pressurised hole breakage technologies. It is also possible that two techniques known as the pulsed laser and pulsed water jets may have some potential. The generally agreed specifications for a widely applicable underground hard rock excavating machine are - disc cutter based, a minimum production rate of 100 t/h, be flexible, manoeuvrable and deployable, weight of less than 100 tonnes and be economically competitive with D&B in rocks over 150 MPa UCS. Such a machine would seriously challenge the position of conventional D&B in a wide range applications and provide some of the benefits of mechanisation and automation that the mining industry is pushing so hard for. However, technology developments in the D&B area are not static and hence the target is moving and is increasingly difficult to overtake.

Jan 1, 1995

It is indeed an honour to address the perth branch of the australian institute of mining and metallurgy and to have the opportunity to talk to you about the future role of upgraded ilmenite on t102 feedstock supply and demand. There have been many papers written on upgraded ilmenite supply and demand and now I would like to share with you QIT's view of the situation first, a word about demand, although I will be talking principally on the supply issue. The principal use of t102 is in the manufacture of pigments which, in turn, are used in paints, plastics, and the paper industry together with a few miscellaneous uses, while a further b% or so of t102 minerals are consumed for the manufacture of titanium metal and for the manufacture of welding electrodes. the total demand for contained t102 is of the order-of 3 million tons per annum, and the general consensus in the industry is that growth rates should be of the order of 2% annually- it is against this backdrop that suppliers must compete with one another and produce least cost materials for the pigment industry. At the moment, supplies are relatively tight, but the generally slow growth in demand coupled with the abundance of titanium bearing minerals should ensure that long term the reverse is generally true. Now, let us examine the supply situation. Titanium is the 9th most abundant element in the earth's crust, so the problem from the producers` point of view is not one of scarcity of titanium minerals, but of how to extract most economically t102 feedstocks from a wide variety of choices- up to the present, all titanium feedstocks are being derived from either rutile or ilmenite rutile, at about 95% t102 content, is indeed a premier raw material which does suffer from potential scarcity and rutile supplies will likely be a diminishing factor in future decades- whereas ilmenite, a combination of iron and titanium oxides found in varying ratios, may be found in huge quantities all over the world.

Jan 1, 1986

By S C. Dominy

The Minerals Education Australia program is offering a tertiary learning environment for the global mining industry. The Minerals Council of Australia has instigated this initiative, which is run by the Minerals Tertiary Education Council. The program is a pioneering partnership between the Australian minerals industry, Australian governments and key Australian universities. It is designed to deliver key undergraduate and postgraduate courses for tomorrowÆs minerals industry professionals in the fields of geoscience, mining and minerals engineering and metallurgy. The flagship course for geoscience professionals is the G3 Masters program. This is a coursework-based degree supported by the Minerals Tertiary Education Council, and a partnership between James Cook University, the University of Tasmania and the University of Western Australia. These partners represent the leading-edge providers of minerals geoscience education and R&D in Australia. The G3 program provides the full spectrum of post-graduate training skills in exploration, mining and economic geology topics.

Jan 1, 2003

By H Beucher

The uranium grade in roll front deposits is the result of successive processes that can be summarised in two steps. First a sedimentary phase, which gives the deposit support, then an oxidation-reduction phenomenon, which leads to the uranium deposit itself. In order to simulate such a deposit, it is important to mimic these different phases. The final aim of such a study is to localise the uranium itself and to reproduce the internal heterogeneity of the orebody in order to simulate the recovery process. The idea in this paper is not to reproduce a genetic approach but to consider the final image of the deposit. Three approaches are proposed. The first one consists of simulating the facies of the sedimentary deposit. The second approach reproduces the distribution of facies resulting from oxidation phenomenon (reduced or oxidised facies). The third approach consists of simulating the mineralisation at the interface of reduced and oxidised areas using the definition of a new data set determined by the grade values. At the end of each approach, the uranium grade could be simulated facies by facies according to the corresponding distribution characteristics. The plurigaussian method dedicated to random set simulations is well-suited for the facies simulations of deposits resulting from several sedimentary processes whether correlated or not. In this paper, the benefit of this method is demonstrated in an actual case study.

Jan 1, 2006

The methods employed in dressing 'the tin ore up to the required percentage of purity depend mainly on the type of ore crushed.These may be briefly divided into two distinct classes-viz., q, free: milling ore and a complex milling ore. In the former the ore is practically free from the common metallic sulphides, such as pyrites, mispickel, blende, galena, etc., and 1!' clean concentrate of 70 per cent metallic tin can be directly obtained in one continuous act of concentration; in the latter, however, in order to get a good extraction, it is only advisable to primarily concentrate up to 30 to 40 per cent. tin oxide, the rest being the sulphides of the metals. This concentrate is then roasted, re-ground, and re-concentrated up to 70 per cent. metallic tin on a separate set of tables.In the complex milling ore the tin is intermixed very closely with the sulphides, so that it becomes necessary to collect all the mineral present in order to obtain clean tailings. Stamp mills are the most popular machines for the primary crushing in the district, but whether they are invariably the best for the purpose is rather an open question. No doubt for some of the very tough chloritic ores they are the most efficient, but for a brittle quartzose ore, such as the free milling proposition usually is, the writer thinks Oornish rolls would well hold their own, especially when the tin occurs coarse, as is so often the case with this class of ore. Of course, the great drawback to stamps is the excessive quantity of tin slimed and slime tin is one of the problems of tin-dressing-while rolls give...

Jan 1, 1907

By P Murthy, Z Guan, P Townson

In this paper, we introduce a methodology to optimise mining equipment operation in terms of the conflicting concerns of productivity and availability. We also introduce the concept of damage points and equipment dutymeters. These provide the mine management with tools to monitor the success of such optimisation. Since we have quoted the results of an on-going Australian Coal Association Research Program (ACARP) project, the apparent focus of this article is on draglines. However, the concept is equally applicable to other equipment. Mining is the type of business that requires a large investment in capital infrastructure and equipment to produce a product that is sold at a relatively low unit cost. In such a business, the key to competitiveness lies in achieving the full realisation of capital investment ie sustained production at high levels. Some of the concepts outlined in this paper are essential components of this picture.

Jan 1, 2000

Surface oxidation is one of the most important factors that influence the flotation selectivity and recovery in the processing of complex sulphide ores. It is an inherent part of surface chemical reactions that determine whether the surface film formed on a sulphide mineral will act as a hydrophobic or hydrophilic one. Because of the highly complex surface chemistry and mineralogy involved the results of flotation tests may often be difficult to interpret. In this paper, the flotation behaviour of nickel-copper ores processed in the Sudbury area is discussed with emphasis on the effect of oxidation on individual minerals, primarily pyrrhotite. In general, moderate oxidation of a freshly ground ore promotes the flotability of all principal sulphides in the ore leading to a bulk flotation concentrate. The ease of individual mineral flotability under normal aeration conditions, which is chalcopyrite > pentlandite > pyrrotite, changes to pentlandite > chalcopyrite > pyrrhotite under oxygen-deficient conditions. This behaviour is correlated with the catalytic activity of these minerals for oxygen reduction. On the other hand, preferential oxidation of pyrrhotite may lead to a selectivity increase in flotation. Such a behaviour has been noted in the flotation of a pyrrhotite-rich process stream. The results have been discussed in the light of fundamental electrochemical interactions involving pentlandite, chalcopyrite, pyrrhotite, pyrite and grinding media and a mechanism has been proposed to explain the selectivity.

Jan 1, 1993

By Haartti J

Generally when equipment is chosen for solving a dewatering problem, the equipment is based on one of following physical methods: gravity (sedimentation, screens), vacuum (vacuum drum and disc filters, belt filters), pressure (filter presses, hyperbaric filters) and centrifugal forces (centrifuges). The choice of method and type of equipment depends, among other things, on the requirements on the maximum water content allowed in the filter cake and on the particle size distribution and the concentration of solids in the material to be dewatered. All the above-mentioned equipment has its benefits and drawbacks. The conventional vacuum filters of drum or disc type are of a simple construction with few parts to be replaced, but these filters produce a filter cake with a fairly high moisture content, and a dryer is required for additional drying. In most cases the use of pressure makes it possible to produce filter cakes with the desired moisture content but the equipment is of complicated construction, leading to high maintenance costs . In addition to this the consumption of compressed air is high. The capillary filtration to be described in this article is a dewatering method which combines the benefits of both the conventional vacuum disc filter and the filter press. The capillary filter produces low cake moistures with a machine of very simple construction similar to that of the vacuum disc filter.

Jan 1, 1993

In order to maintain an accurate survey underground, it is first necessary to connect all shafts used for the transferring of the survey to the levels below by a precise surface survey.This has been achieved at Mount Isa by a careful triangulation survey with stations adjacent to those shafts most suitably located for transferring the survey below.The precedure used is described herein.The Weisbach triangle commonly used is obtained by reading to swingirig wires, the theodolite being placed in line with them as nearly as is possible. The surveyor at the surface places the wires in the shaft as far apart as the size of the shaft will permit, with sufficient space between the wires and walls to ensure their swinging freely. The far wire is fixed in position, while the near one is movable by means of fine adjusting screws to facilitate its being brought into line with the fixed wire and the theodolite. When this is done the surveyor at the lower level is advised by pre-arranged signals and the survey can then commence.The surface portion of the survey is simple; all that is necessary being to read the angle from the backsight to the wires, measure their distance from the theodolite, and keep a check on them throughout the survey to make sure that no movement takes place.The lower portion of the survey is more difficult, the surveyor first qf all having to place his theodolite as nearly as possible in line with the wires.

Jan 1, 1953

By Best R, Poulos H

This paper discusses the results of an Australian Coal Association Research Program project into the development of a routine analytical design method for roof support in underground mines. Simple design tools have been developed using a combination of elastic solutions, free body diagrams, and pile theory. An approach to the design of roof support in layered strata based on the ability of bolts to resist shear stresses is outlined. It is shown that pre-tensioning and angled installation are effective ways of increasing the effectiveness of bolts in such a situation. In highly stressed strata, macroscopic failure is predicted and a design based on the support of surcharged rock wedges is proposed. The methods are applicable to both coal and metalliferous mines.

Jan 1, 1995

What is the best circuit to comminute primary crusher product to make beneficiation feed? Finding the best circuit to crush and grind minerals to beneficiation sizes is a complex problem that can lead to interminable discussion. Conclusions reached can be questioned. This will continue as long as the technology of comminution continues to expand, and is a mixture of many technical and economic factors in what is not a precise science. Laboratory and pilot plant procedures now exist that can help process engineers make sound decisions on which circuits are the best for crushing and grinding the specific ore being studied. It is the aim of this paper to discuss such procedures so a better under- standing of key decision parameters is avail- able, and to update comminution testing which has seen a. period of change in which new procedures have been introduced.

Jan 1, 1978

IT is very difficult for a founder engaged in jobbing work, comprising all sizes and classes of castings, to appreciate that the analysis of the iron he is using cannot entirely fill the situation he desires for his varied classes of work. Neither is there any panacea in the shape of an iron mixture that will suit the whole of his floor for the day.From his own experience he generally alters his cupola charges during the cast, endeavouring to meet at the same time the requisite metal composition for the castings he is about to pour.The founder on repetition work is in a much better position to stabilise his methods, arrive at a certain pig-iron' analysis, regulate...

Jan 1, 1926

By Cornell J. B

Scaling in Bayer Refineries is a natural consequence of the super-saturated liquors used in the process. The caustic liquor is supersaturated not only with alumina but also silica and calcia at various stages of the process. The basic scaling mechanisms are reviewed and examples of the two basic types, growth and settled scales, are given. Examples include gibbsite scales formed in the precipitators and silica scales formed in heat exchangers. The main factors affecting the rate of growth of growth scales are temperature and supersaturation and are highlighted using a silica scale example. For growth scales chemical cleaning rates can readily be predicted from kinetics and an example for a gibbsite scale is given. For settled scales the growth rate cannot be predicted and the hydrodynamics within the system have most effect. There is no simple method to predict the potential for chemical cleaning of settled scales; some of the relevant issues are discussed, in particular methods to identify the cementing phase in the scale. An example of design considerations for a scaling system, transport of slaked lime, is Given.

Jan 1, 1996

Working thick coal seams in Poland is a very serious problem. Nearly 40 per cent of all coal is extracted from seams more than 3 m. thick. In absolute figures this represents about 70 million tons of coal per year. Working seams with thicknesses up to 3.5 m. does not present, at present, major difficul- ties. Working thicker seams calls for a steady improvement in order to increase the degree of utilization of the deposit and to enlarge the concentration of output. The problem is sometimes more difficult because, in many cases, the seams are worked under protected surface structures which compels the mines to use hydraulic stowing with all its advantages and disadvantages. Rock burst hazard, the control of which is the basic problem hindering the mining, is a further problem. The mining systems used in Poland are adapted to these natural and technical conditions.

Jan 1, 1976

By O&apos, Malley G. B

The properties of bearing metals are of considerable interest to mine engineers, since continuous running of mine and mill machinery is of vital importance. Of the several available types of bearing metal, the low melting point lead or tin base alloys are most generally used in mining plant because of the ease of replacement and the possibility of remelting scrap metal from old bearings. The most valuable property of these "white metals," however, is the plasticity which gives a self-aligning character to the bearings, enablingthem to adjust themselves to inequalities which may exist at the time of fitting, or which may develop during running. The object of the present paper is to explain in general terms the physical structures of white bearing metals, and to point out that constitution rather than composition determines the physical properties of these alloys. The same, indeed, is true of most engineering alloys. In steels, for example, a change in the structure may affect the properties to a far greater extent than a change of chemical composition.Structural changes in steels are produced chiefly by heat treatment. In the case of bearing metals no good purpose is served by heat treatment; the microstructure is determined by the conditions of casting, and striking differences in constitution (and therefore in properties) are encountered in an...

Jan 1, 1932

By Whincup P

Hilton deposit comprises en-echelon silver-lead-zinc orebodies with reserves in excess of 50 million tonnes. The host rock to the ore is a dolomitic and pyritic shale/siltstone which dips steeply west. The shale/siltstone is deeply leached and porous, particularly over the Ore Zone where the depth of leaching continues down to 440 m below surface, and constitutes an extensive permeable aquifer system containing a large volume of saline acidic groundwater. Initial production commenced at Hilton in 1987 well below the aquifer. A dedicated dewatering and monitoring programme is in place to ensure security of stoping operations and allow extraction of ore close to the leached zone in future years. Dewatering is undertaken from controlled bores from underground sites. Mine groundwater discharge is presently at the rate of 4000 kl/day with plans to increase to 8000 kl/day. An additional 2000 kl/day of fill and service water and water from secondary aquifers is also pumped from the mine daily. Although recharge rate to the aquifer is minimal, studies indicate that due to the size of the aquifer and future extensions to mine development, dewatering will be a life of mine activity. The investigations which have been undertaken to determine optimum dewatering techniques and schedules are described. These include production bore tests, mine planning constraints and computer aquifer modelling. Gravity geophysical techniques have been successful in delineating the lateral and vertical disposition of the aquifer. The mine dewatering schedule, whose principal component is underground mine drainage, is also outlined.

Jan 1, 1988

Infrastructure is defined as all those parts of a mining development which are not directly concerned with mining and mineral processing. Infrastructure is of significant and growing importance in the overall develop- ment of mines, and the costs could be critical in determining the viability of a project. Prior to_project authorisation, feasibility studies are required, often in considerable detail, to determine costs with adequate reliability. It is necessary that the Engineer should be adequately briefed for carrying out these studies and that good liaison and communication with the Owner be maintained. Methods, costs, order of accuracy, and some special requirements of these studies are discussed. After project authorisation, rapid im- plementation of the proposals is generally desired. A suggested organisation and method for this implementation is presented and dis- cussed. Comments on fees, and particular points in the relationship between Owner and Consulting Engineer are given. Particular reference is made to differences in conditions compared with public works projects. Realistic attitudes of mind towards environmental matters, industrial relations, and contractual relationships are advocated.

Jan 1, 1974