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In process industries, time-dependent random fluctuations of raw material characteristics and mass flow rates in bulk material or pulp flows cannot be always prevented for different reasons, eg because of the geological situation (no uniform formation of the deposit) or/and because of technological reasons (segregation in bunkers or on stockpiles). Since a long time, there has been practical experiences that such fluctuations can have negative consequences, eg: ò fluctuations of the final products characteristics, ò higher expenditure for process control, and ò worsening of technological characteristics (recovery, sharpness of separation etc). In the literature, there can be found a lot of details as to, eg the improvement of the sharpness of separation in a jig in dependence on the raw material blending (Kubitza, 1981; Gathen, 1983) or the decreasing flotation recovery with increasing raw material characteristics fluctuations in iron and potash ore processing plants (Bubnova, 1978). Up to now, however, these consequences of random fluctuations, eg on the separation efficiency were not predictable theoretically. It could be shown by means of the general model for mechanical macroprocesses (Graichen, 1989), that the reduction of input fluctuations passing a blending facility can be calculated in this way. In this example, the steady state of the process is the wanted one, but, in general, the model is able to describe also non-steady states of the process regarded. On the other hand, the general model of mechanical macroprocesses has been used successfully for modelling separation processes, eg cross-flow and air classification (Molerus, 1969; Neesse, 1991; Senden, 1979; Tichonov, 1973). That is why it was tried to model the influence of input fluctuations on the separation efficiency, that means, the impact of non-steady states - as a consequence of random fluctuations - on a separation process. The models discussed in the literature are related nearly exclusive to the steady state of the process. The reasons for that lie in the (relative) simplicity of the models and the fact that the steady state is aimed at by means of blending processes under practical conditions - because of the advantages mentioned above. These models cited have proved to be superior to other models, since the basic general model for mechanical macropocesses makes possible the consideration of turbulence acting in the process unit and influencing the separation process essentially. This is valid also for modelling the turbulent cross flow classification, applied to mechanical classifiers and hydrocyclones, where the correspondence between the separation characteristics (cut size, separation sharpness) calculated and determined experimentally is much better than for other models.

Jan 1, 1993

By Slechta JJ

The performance of a hydrocyclone treating fine coal has been examined over a wide range of feed and operating conditions.The results were expressed in terms of partition curves from which the water split to the oversize flowstream,the corrected separation size and reduced partition curves were determined-.The following conclusions were obtained. (a) The water split to the oversize flowstream was found to be dependent upon the vortex finder and spigot diameters of the cyclone and the flowrate and solids content of the feed slurry. (b) The corrected separation size was dependent on the solids content of the feed,and the vortex finder and spigot diameters.The hydraulic pressure (or flowrate) of the feed slurry did not have a significant effect.This phenomenon could be explained in terms of crowding of the particles at the Spigot.

Jan 1, 1984

By P Benjamin, H Bohannan, C Farr

Geoffrey Blainey's historical account of the mining activity on the west coast of Tasmania, æThe Peaks of LyellÆ documents the changes over 130 years of activity in the region. Commissioned by the Mount Lyell Mining and Railway Company, emphasis is placed upon the development of the Mount Lyell Mine in Queenstown. Chapter 19 æWidening HorizonsÆ details the review the Mount Lyell Company undertook in 1904/05 to ensure the future of the operation, following the pessimistic outlook regarding diminishing reserves and poor grade ore. The analogies documented between the Mount Lyell Company at that time, and Gold Mines of Australia 90 years on are remarkable, with both companies demonstrating a commitment to the Mount Lyell area through active exploration, the proactive search for alternative technology and the recognition of the valuable human resource. As Blainey writes (Blainey, 1993), æwith its expanding chemical works, its huge Tasmanian mines, its railways and smelter, its coke works and its mine crusade, Mount Lyell was probably one of the nation's five great industrial companies in 1906 or 1907. This brief phase of industrial and mining expansion had its seed in the threat of extinction . . .Æ After a number of reprieves, the Mount Lyell mine did stop production in 1994, but that only provided an impetus for a review and rebirth.

Jan 1, 1998

In a previous paper in these Proceedings(l) it was shown from a study of the bore'logs and analyses then available, that the brown coal seams of the Latrobe Valley areas show progressive changes in composition with increase of stratigraphic depth, equivalent to a rise in rank: These changes appear as:(i) An increase in ultimate carbon and hydrogen, calculated on a dry, ash-free basis, and(ii) An increase in calorific value, calculated on the, same basis, each of the order of 1% per 100 ft. of depth, and(iii) A decrease in moisture content of the order of 0.5% to 1.0% per 100 ft. of depth. The decrease in moisture content was found to be less regular than the other changes. In some bores the moisture content remained more or less constant throughout a single seam, or fluctuated slightly, decreasing stepwise on passage to the seam below.It was noted that individual analyses within a bore showed irregular fluctuations, tending to mask the general trend in composition change. This was particularly so for the moisture content, which had been determined for 10 ft. lengths of core, whereas the other components were determined for 50 ft. lengths of core. Averaging of the moisture contents over 50 ft. lengths reduced the masking effects of these irregularities. The suggestion was made that these irregularities arose from variations in the relative proportions of pollen, resin, wood (lignite) and woody attritus composing the core. Such variation in the coal seams has since been established in some detail for the...

Jan 1, 1948

Records of ex-solution intergrowths with tetrahedrite as a component are rare. Intergrowths of this nature of tetrahedrite with galena have been described by Guild (1917) and Schneiderhohn (1922), and in Broken Hill ore by Stillwell (1926), but both Schneiderhohn (1922) and Gruner (1929) have commented specifically on the apparent absence of exsolution intergrowths of tetrahedrite and chalcopyrite, despite their frequent association in ores, and their related atomic structures. Schwartz (1942), reviewing the literaturerelating to ex-solution among ore minerals, lists only two instances of such intergrowths, one an occurrence of lamellae of chalcopyrite oriented along the octahedral planes of tentantite (the arsenical isomorph of tetrahedrite), the other of blebs of tetrahedrite in stannite. The only other possible instance of such intergrowths known to the author is the record of "pseudoeutectic" intergrowths of tetrahedrite with chalcopyrite and with bornite in a silver pitchblende ore from the Great Bear Lake district of Canada (Furnival,1939).Some interest attaches, therefore, to the two occurrences described below of tetrahedrite showing ex-solution relationship, in one instance with chalcopyrite, and in the other with bornite.TETRAHEDRITE-CHALCOPYRITEAn intimate intergrowth of tetrahedrite and chalcopy-rite, apparently the product of unmixing of a solid solution of...

Jan 1, 1946

By Goldstone A

The paper introduces a newly developed multi-function test rig for fracture grouting. This test rig has many functions and its performance is consistent. It can control and adjust accurately the opening degree of fissures and static pres- sure; it can measure automatically the quantity of grout injected; it can measure precisely pressure drop of grout in fissures; it can test the results of injection, including effective dispersed distance, anti-filtration capacity of consolidated body, mechanical strength, etc. It can inject a single or two grouts into one or several fissures at a pressure of 16 MPa. Therefore, it is an ideal test rig for fracture injection. The paper depicts all the components of the test rig, its performance and application of the results obtained from fracture grouting tests. Examples are briefly described.

Jan 1, 1988

By Cornwell P. J

The Pajingo ore bodies consist mainly of auriferous quartz veins hosted by a suite of hydrothermally altered andesitic pyroclastics, volcanics and epiclastic sediments. Scott lode, the main economic deposit in the area, lies in a zone of major structural disruption and contortion. High grade gold and silver mineralisation is selectively mined by open pit methods. Standard grade control techniques and extraction methods were adapted to minimise mining dilution and to maximise metal recovery. Basic blending of grade ranges at the crusher has produced an average 10 gram/tonne gold head grade. The estimation of ore reserves calculated by both standard polygonal and geostatistical methods proved acceptable. Mineable reserves when compared to in pit reserves defined by blast hole drilling, indicate a decrease in tonnes and an increase in the grade resulting in an acceptable comparison of the total ounces of contained gold. The ore reconciliation of mined against milled ounces indicates that both ore reserve and grade control models underestimate the metal content in the orebody. Sampling techniques are being examined in an attempt to reduce this discrepancy.

Jan 1, 1989

The Sto Tomas II orebody of Philex Mining Corporation is a porphyry copper deposit located at Padcal, Tuba, Benguet, Philippines. It was mined through open pit method for the first two years starting 1958 and subsequently through underground method using the Block Cave System. The slusher type of draw was employed at the upper levels of the orebody from mid-year of 1959 up to 1994 and then shifted to LHD as the ore became more competent at the lower levels. Application of rock mechanics played a vital role during the conceptualisation of the LHD method of draw, the first of its kind in the Philippines. Rock mechanics is a combined responsibility of the geology and the mine engineering staffs, with the geology providing the vital information to the mine engineering to include in the mine planning the following:the general geology of the orebody; the ground characterisation through rockmass classification; determination of the cavability of the ore column (this includes our experience on airblasts which occurred during the early stage of our last slusher blocks); undercutting sequence; fragmentation of the rockmass in the ore column; drawzone spacing; proper draw control procedure; lay-out of openings; and the design of ground supports based on the rockmass condition. For the proper interpretation of the rockmass that would cater to the diverse mining situations, Philex adopted the modified geomechanics rockmass classification (Mining Rockmass Rating, MRMR) as this system is recognised and used by most of the block cave mine worldwide. This paper aims to discuss and present the role of rock mechanics in the analysis and determination of geomechanical issues encountered in Philex mechanised block cave operation.

Jan 1, 2000

By Wilkinson RDB, Van Der Meer FP

In order to overcome the statistical limitations imposed by the need to recover density tracers by hand, magnetic density tracers were developed to determine the efficiency of dense medium separators treating porous materials. The tracers were manufactured by extrusion of polypropylene ferrosilicon mixtures and subsequently coated with a distinctive paint to allow hand sorting according to density. Fifteen tracer batches were manufactured in the range 1.61 - 1.94 g/cm3. The tracer densities were determined by a hydrostatic method. The tracer method was applied to the dense medium separation of a Moroccan oil shale in a pilot scale Dyna Whirlpool separator. For each test, about 20,000 tracers were added with the plant feed and subsequently recovered from the products with a dry low intensity magnetic separator. The Tromp curve determined by conventional heavy liquid analysis was displaced towards lower densities compared with that determined by tracers, indicating that the porous shale particles absorb heavy liquid. It is concluded that for porous materials like oil shale and coal, the tracer method gives the most accurate results. In pilot scale testwork the tracer method is also much faster than the conventional heavy liquid analysis, as rather large samples have to be processed by the latter method to ensure Representativeness.

Jan 1, 1987

By Ross R

Although mining is an old industry its management is quite a new science, and its complications are now being recognised as demanding expert knowledge in many branches of technical and professional education. Not the least amongst these isaccountancy, for probably its most important problem is "How to control the expenditure." Unlike most businesses a mining company stands almost entirely in the light of a purchaser in the world's markets, and not as a seller, except say for product so the established and perfected systems of modern industries cannot be adopted for mining purposes. For this reason it has been left for late years to consider the matter seriously, and now a number of well-managed concerns have devised costs systems to suit their own requirements.Very little, however, has been published and even that is disjoined and difficult to make use of. Some of the costs systems in vogue, although elaborate and imposing, are not of very great value for keeping check on wasteful expenditure, or for displaying the commercial effect brought about 'by any particular change in practice, or by an addition or alteration to a portion of existing plant.

Jan 1, 1911

Tyre cost at Mount Morgan Limited had been 24% of the truck operating cost. Comprehensive tyre testing resulted in a reduction in tyre costs of about one third. A record of the evaluation techniques may enable the selection of tyres that are most suited to particular conditions. Rubber characteristics, rubber quantity, tyre design, road conditions, dump conditions and inflation pressure were found to be sig- nificant variables. Measurements of tyre temperatures at the breaker strip were used to select the tyre design and inflation pressure required for Mount Morgan Limited's conditions. Relugging of tyres was discontinued as a result of tyre testing.

Jan 1, 1974

By Binns RA, Murao S

The PACMANUS and Jade deposits are two active hydrothermal fields that are forming massive sulfide deposits at the Pacific rim margin. Both are associated with felsic submarine volcanic rocks and both occur in back-arc settings. However, PACMANUS is associated with almost sediment-free dacites and lies on the crest of a volcanic ridge, whereas Jade occurs in a heavily-sedimented tectonic depression associated with a basement of pumiceous rhyolite. The PACMANUS deposit is richer in Cu and Au, and Jade in Pb. Zinc, Ag, As and Sb contents are similar. Sulfide textures at PACMANUS suggest formation of Cu and Zn sulfides by simultaneous double-diffusion involving inwards-moving seawater mixing with outwards-moving hydrothermal fluid. By contrast, at Jade there is a more complex history of formation where initial growth of barite on the sediment surface, probably associated with microbial activity, formed an impervious cap which trapped higher temperature hydrothermal solutions.

Jan 1, 1995

The variation of austenitic grain size with temperature for the steels XKSlSO and XK9261 was determined using the vacuum ctching technique.It is shown that the effect of temperature on the mean grain intercept is relatively small, up to approximately 950°C. Above this temperature the rate of increase of grain size rises sharply.Within the limits of the 1-4 hr vacuum etching times used the effect of time at temperature is relatively small on the ASTM grain size of the steels.

Jan 1, 1967

By Weir D. R, Doyle B. N

The Sherritt Zinc Pressure Leaching Process is based upon the direct pressure leaching of zinc sulphide or lead-zinc bulk sulphide concentrates to produce zinc sulphate in solution and elemental sulphur in the leach residues. The zinc sulphate solution is compatible with conventional purification and electrowinning technology. The pressure leach residues can be treated for the recovery of elemental sulphur, lead and silver. With the conversion of sulphur to the elemental form, zinc pressure leaching allows zinc winning to be independent of sulphuric acid production. Direct pressure leaching of zinc sulphide concentrates was started commercially in October 1980. Continuing research and development studies have defined various pressure leaching configurations for integration with existing roast-leach operations, for grass roots plants, or for plants which are to have the roast-leach section completely replaced. These studies have included the treatment of zinc concentrates from various Australian producers and the development of process flowsheets for potential applications in Australia.

Jan 1, 1989

By Upfold RW, Nguyen VU

The extraction and utilisation of metals and materials is the basis of modern civilisation, and will remain so for many decades, Traditional metals are facing some challenges and research is needed in specific areas, to improve metal extraction processes, to develop processes for newer metals and minerals, and to develop new applications, The shortage of metallurgists now becoming apparent in Australia is a further significant problem that needs urgent attention, and much more publicity is required for the Mineral Industry, as well as for the utilisation Industries,

Jan 1, 1986

During 1991 - 1993 the author interviewed approximately thirty senior managers of varying responsibilities in either the engineering, construction or operation of a heavy industrial facility. The purpose of the exercise was to determine the factors driving a deterioration of the working relationship between the engineering and the operating company following practical completion of a major project. From the research a number of conclusions have been drawn as to the root cause of the deteriorating relationship. For this paper we are drawing on this initial research and our ongoing experience of solving problems of this nature to present some fundamentals that can be used to break the breakdown maintenance cycle.

Jan 1, 1998

King Island is situated at the western approach of Bass Strait and approximately mid way between Victoria and Tasmania. The scheelite orebodies lie within the south east of the island. Ore bearing horizons from 10 m to 40 m thick occur in south and east dipping stratiform deposits. The orebodies occur in skarn formed by contact metasomatic replacement of carbonate rocks by granite intrusives. The scheelite is deposited as fine disseminated grains in and along the margins of andradite garnets in the skarn. King Island Scheelite operates two under- ground mines from which 350 000 tonnes per year are obtained. The Dolphin mine produces almost two-thirds of the total. See Figure 1. The Dolphin orebody lies beneath the sea and an area of reclamation. The orebody is inter- sected by zones of major dislocation. A chequerboard post pillar cut and fill stoping system has been chosen to provide the necessary support to the hanging wall. Because the stability of the pillars is critical to the economic welfare of the mine, considerable attention is given to the reduction of overbreak.

Jan 1, 1977

By S B. Martin, M P. Simpson, J L. Mauk

The Martha deposit in Waihi, New Zealand, is a giant adularia-sericite epithermal gold-silver deposit that formed 6.0 to 6.1 Ma, and has produced over 6.4 Moz gold and 39.9 Moz. Fluid inclusion analyses were undertaken on a limited number of vein samples from Martha. The results from this eight week student project are preliminary but agree with previous studies. There is little variation between primary and secondary inclusions and between different vein types, except that homogenisation temperatures of the inclusions in sphalerite grains are on average 20¦ to 30¦C higher than the average quartz vein values. Overall the temperatures of homogenisation ranged from 182¦ to 258¦C and final ice melting temperatures ranged from 0.0¦ to 2.8¦C. Unusual black inclusions were also found associated only with the ginguro bands. Some of these appear to be solid sulphide inclusions but others are not so clear.

Jan 1, 2007

By Botz R. W

Macroscopic and microscopic studies of the outburst-prone Gemini Coal (Bowen Basin) showed that outbursts were associated with a localized inertinite-rich ply. Previous studies of the Gemini Coal had shown a general relationship between desorption rate, regarded as a good measure of outburst proneness, and inertinite content of coal samples.Desorption rates increased with increasing inertinite content and were highest for inertodetrinite-rich samples. These results suggest that inertinite content and composition play a significant role in outbursting and may be useful in identifying outburst-prone coals, which could be confirmed by desorption measurements.Consequently outburst-prone areas in the Upper Permian coal measures ofthe Sydney, Gunnedah and Bowen Basins have been defined using a combination ofthe parameters, inertinite content, depth ofcover and coal rank. In the Upper Permian, inertinite-rich coals are confined mainly to the top of the coal measures, except in the Sydney and Gunnedah Basins where an inertinite-rich interval (Bayswater Coal and correlatives) is also present towards the base of these measures. Only a small area ofthe central Sydney Basin, butmuch ofthe north-eastern and north-central part of the exposed Bowen Basin is considered outburst prone on the basis of these parameters.The most outburst-prone inertodetrinite-rich lithologies have a patchy and unpredictable distribution in the top of the Upper Permian coal measures. They can be defined only by sampling and petrographic analysis at the subsection level.

Jan 1, 1986

By R C. Schodde

The future of any mining company depends on maintaining and growing its access to high-quality mineral resources. Often the true size of a given resource is not fully recognised until after mining has commenced. Also, the strong desire to increase production puts pressure to expand the resource base of the mine to get maximum value out of the capital employed. This, plus diminishing M&A opportunities and declining world-class greenfield discovery rates, makes brownfields exploration a high priority activity in any operating company. For the success and long-term survival of the company it is critical that this is done well. The primary aim of brownfields exploration is to find or acquire new deposits within economic transport distance of an existing mine that will add materially to shareholder value through: mine or capacity expansion, displacement of lower-margin ore from the mine plan, preserving and extending the mine life, and ensuring potential value is understood in order to maximise potential future mine development or exit. A number of strategic principles are important in any program designed to achieve these aims: understanding the life of mine (LOM) production profile and the related key drivers for exploration, understanding the dynamic nature of the brownfields search space, understanding and measuring depletion of the brownfields search space, understanding the potential of the near-mine region, investing in exploration technology to expand the search space, and investing in a basic geological understanding of the ore-environment. Examination of the LOM profile will highlight critical issues facing development plans for the mine including future grade and throughput issues, key technology requirements or innovations and scenarios for increased production. Exploration targets in the brownfields program should address these key issues. Often it is as æsimpleÆ as keeping mine development sufficiently far ahead of extraction to allow time for the various phases of exploration and resource assessment drilling. Because of the low additional capital costs required, expansion of the brownfields search space is strongly leveraged to: metal prices, development of new markets, incremental operating cost reductions, strategic changes in downstream requirements in integrated businesses, depletion of higher unit-value ores, and new technologies (both extraction and exploration). Therefore the brownfields search space is likely to incrementally expand through time and must be regularly reviewed. This is also important as any given search space will be progressively exhausted, resulting in smaller and higher cost discoveries. It is therefore important to monitor and critically review sustained trends of increasing brownfields discovery cost. The first wave of discoveries in any camp are usually empirically driven and do not need a strong geological understanding. However, an improved geological understanding is critical to making the next generation of hidden discoveries. To illustrate these points, a case study was carried out on the exploration and development history of the Kambalda nickel camp. Over a period of 40 years, more than 40 deposits were found containing over 1.7 million tonnes of nickel metal. Efficient mines need to maintain reserves for operating flexibility. Consequently, the company needs to clearly understand the global resource in order to maximise its full potential. In addition, understanding the full brownfields potential earlier in the development of a deposit rather than later, creates optionality through the flexibility that this understanding brings to future development choices. To ensure best practice in attaining this aim, the roles and responsibilities of the exploration team and the mine operation should be clearly understood. It is important for the explorers and the operators to have shared views about what needs to be done. Typically, mine operators would be accountable for identifying future resource requirements to support the life-of-mine production schedule whilst explorers would be accountable to ensure best-practice assessment of brownfields exploration opportunities. This would include an assessment of the global undiscovered endowment in the regional near-mine area. The balance between brownfield exploration drilling and resources to reserve conversion will need to be decided to ensure efficient operations are maintained. Both need to agree the optimum level of brownfields funding taking into account: urgency to replace or grow reserves, and quality of opportunities (relative to those elsewhere). The ultimate cost of ignoring the full brownfields potential of an operating asset can be significant, ranging from inefficient and poorly planned operations, lost opportunity cost and resultant value through under-utilised resources and, in the worst case, early exit from the asset at the bottom of the commodity cycle û leaving behind huge amounts of shareholder value.

Jan 1, 2006