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By P Hofmeyr, D Pretorius

Iron ore, which is transported by rail from the iron ore mines at Sishen in the Northern Cape, to the Saldanha Iron Ore Terminal in the Western Cape, needs to be analysed while loading to be exported. Every shipment will be sampled and an average analysis of the ore will be produced which is required by the purchaser at the receiving port. On arrival at the iron ore terminal at Saldanha, the ore is tipped from the rail trucks onto conveyor belts to be either stockpiled or direct-loaded. The conveyor belts run under the sampling plant and the ore is sampled periodically by means of an automated cross-belt sampler. This is the first iron ore port sampling facility in which the automated sampler is situated above the conveyor belts and not adjacent to them. A portion of the primary sample taken off the belt is moved to the dedicated sampling laboratory situated behind the cross-belt sampler and over the conveyor belt lines. The sample is split in the laboratory, one split being used for moisture and particle size determination and the other part is dried and then analysed by means of X-ray fluorescence spectrometry (XRFS) on fusion beads for major and minor elements. Particular care is taken to obtain high quality data for penalty elements.This sampling plant is completely automated and from the primary cross-belt sampler to final analysis by XRFS no manual steps are involved. This has meant that some processes are used which are suitable for automation and are ISO compliant but not necessarily ISO-certificated. The ISO manuals were developed with manual laboratory processes in mind. Precautions are also taken to maintain the integrity and representativity of the samples. This paper is a case study?describing?the automated sampling systems used at the Saldanha Iron Ore Terminal sampling facility and laboratory from conveyor belt to analysis.CITATION:Hofmeyr, P and Pretorius, D, 2012. Automated sampling of iron ore for analysis at the Saldanha Iron Ore Terminal in South Africa, in Proceedings Sampling 2012 , pp 25-32 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 21, 2012

By M Chiquito, R Castedo, P Segarra, L M. López, J A. Sanchidrián, J Navarro

The aim of this work is to assess the performance of different constructive solutions against explosions on the strength of masonry walls. The solutions tested, namely an external metal mesh, a glass fibre film on the external face of the wall and a basalt fibre film located on the inner face of the wall, have low to medium cost and are originally designed for other purposes, like seismic protection. Four cubic boxes 3 × 3 × 3 m were built using each of the solutions and typical masonry blocks. In the tests, a spherical plastic explosive initiated in the centre was placed at scaled distance of 2.9 m/kg1/3, so that moderate damage would be caused on the wall. In order to assess the performance of the explosive, pressure gauges were placed at the wall and at different distances from the explosion. Additionally, vibrations were monitored with seismographs in the far field and a high-speed camera was used to estimate the shock wave velocity during the tests. The resulting damage has been evaluated on 13 points of the external wall of each box using a rebound hammer. Damage maps have been drawn for each wall based on these measurements and damage has been assessed inside the box considering the fragments mass launched during the test. The use of external metal mess leads to a decrease of 34 per cent on damage of the external wall and 38 per cent reduction of spalling. The use of a film in the inner wall provides a strong reduction on spalling.CITATION:López, L M, Segarra, P, Castedo, R, Sanchidrián, J A, Navarro, J, Santos, A P and Chiquito, M, 2015. Performance of different constructive solutions against explosions in full-scale masonry walls, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 819–824 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

The geographical region of South East Asia is variously defined, but generally agreed to include the Asean group - Philippines, Malaysia, Thailand, Singapore and Indonesia. Other regional countries, such as Vietnam, Laos, Burma, Kampuchea etc. are of course geographically part of the region, however in economic terms, they play a minor role. It is the Asean group that dominates present economic activity and provides the overwhelming opportunity for commercial development. My experience in South East Asia has been gleaned over 15 years of regular travel in the region. More recently, we have established company offices in Malaysia, Singapore and Indonesia to extend and deepen contacts with major customers. This progressive development is an integral part of a planned growth pattern and will be discussed in more detail shortly. South East Asia is a rapidly developing economic growth centre, a fact which is clearly recognised and accepted by most commentators. An important question is then to be asked: Why has the region been relatively neglected by Australian, U.S. and European industrial supply companies? I will attempt to address this question in the context of industrial minerals and propose some ideas as to how effective sales programs could be developed. Firstly, let's consider the market potential provided by countries within the region. It is reasonable to suggest that industrial growth in S.E. Asia over the past 20 years has been generally steady and in some cases, explosive. Until recently, this growth has predominantly been driven by development of internal (regional) demand. Population growth and rising living standards have ensured that basic industries have enjoyed a solid uptrend in sales and production. The industries which most benefitted from regional economic development over this period were, interestingly, those which we understand to be major users of industrial minerals - glass, ceramics, paper, surface coatings, cement, refractories, rubber and plastics. Each of these industrial sectors has been influenced by different growth stimulii over a 20 year period. Nevertheless, they also enjoy a common feature which ensured an above average performance. All sectors are fundamental to an environment enjoying rising living standards and rapid growth in general prosperity. More recently, internal growth factors have been overtaken by a recognition that manufactured products from the region are competitive in export markets. This comparatively recent development provides the most interesting possibilities for higher value industrial mineral raw materials. Let me explain: For 20 years, industrial growth in South Asia has essentially been focused on satisfying domestic demand. Finished quality of manufactured items was orientated to a developing market more interested in cost than aesthetics or long life. This was reflected in raw material specifications, which often did not exist and at the best were undemanding.

Jan 1, 1989

Dynamic hydrothermal modeling is a tool that can aid in studying problems associated with hydrothermal ore deposits and can help increase our understanding of the spatial distribution of ore within hydrothermal systems. Models are constructed by a sequence of steps involving development of a conceptual model, followed by its mathematical description in terms of governing equation with accompanying initial and boundary conditions. This equation is then solved either analytically or numerically. The four model types ò that fully describe a hydrothermal 'system are those for fluid flow, heat and ore solute transport, and deformation. At Renison, models have been used to help understand two major exploration problems. These are the controls on ore localisation in dolomite horizons and feeder faults respectively. The types of models used ò have simulated the distribution of all mineral zones, pyrrhotite, and temperature in the dolomites. This has allowed evaluation of the effects on ore localisation by physical and chemical heterogeneities within the dolomite host rocks, and allowed estimation of potential controls in different physical and chemical environments.

Jan 1, 1987

By Oliveira JF

Thiourea is an alternative reagent for cyanide in gold leaching. The recovery of gold from acidic thiourea solutions by adsorption on activated carbon is based on methods similar to those applied for the extracting of gold from cyanide solutions, but the mechanism involved in the process is not completely understood. In the present work, studies were carried out to evaluate the adsorption of gold onto activated carbon. Experimental data showed good agreement with both the Freundlich and Langmuir isotherms. The adsorption of gold from acidic thiourea solutions proved to be an endothermic process, while the adsorption from cyanide is known to be exothermic. The isosteric heat of adsorption of -11.3 kcal/mol in the early stages of the adsorption is an indication of a process involving chemisorption. The effect of temperature was studied between 15¦C and 55¦C. An activation energy of 3.5 kcal/mol was determined by the Arrhenius plot, which indicates that the controlling step in the kinetics of adsorption is the diffusion onto the porous structure of the activated carbon.

Jan 1, 1993

By S M. C Verryn

The amount of raw material used in the production of cement can be reduced by partially supplementing it by pozzolanic waste material without changing its properties negatively. This paper discusses results of an investigation using slag from the Pt industry, from the production of steel using Midrex processes as well as fly ashes from different coal power plants in South Africa. These are blended in a 20 per cent slag or fly ash to 80 per cent cement ratio. The properties of the mixtures depend on the phase composition, chemistry, grain size and the sources of the materials. The results are promising, but show variable behaviour depending on slag and cement composition. Compressive strength tests as well have heat flow curves showing the hydration behaviour, indicating that 20 per cent addition of slag or fly ash to ordinary Portland cement is viable. There is a large potential to use slag in cement mixtures and this study can be used to develop cements that will positively influence CO2 emissions and help to reduce large slag and fly ash stockpiles.

Jan 1, 2008

By M Devia, J Rapkoch

This paper is intended to help design engineers, operating staff and plant managers understand the principles of metallurgical gas handling systems design. It also explains operating, safety and energy savings issues that the designer should take into consideration in the design of process off-gas systems for sulfide smelters. Primary smelting reactors, converters, and other off-gas sources impose challenging duty requirements on the various components of the gas handling systems. This paper reviews the design of common system components including the hood for gas capture at the system inlet, gas conditioning, gas cleaning, ductwork, dampers, hot gas fans, and the appropriate use of instrumentation and controls. The engineer must also be aware of how ductwork system effects and heat losses influence system performance. Also, the analysis of a recently-designed gas handling system will be reviewed, which includes high-strength SO2 gas from a smelting reactor, asymmetrically located Peirce-Smith converters, and a gas mixing chamber to mix the gases before they are sent to two acid plants of different sizes.

Jan 1, 2005

THE alkaline method for the estimation of zinc cannot, in the writer's opinion, be relied. upon to within very narrow limits between two assayers on unknown quantities of zinc. The end point is not decisive enough, and allows the personal factor toenter largely into the assay. The following investigation was undertaken to see how accurate the acid method is on Broken Hill concentrates and ores, and what should be the limit between the results of two assayers. The method adopted is as follows:Weigh sufficient amount of ore to give titration (between 20 and 50 cc.), place in tall 400 cc. beaker, cover, add 7 cc. nitric acid and heat till brown fumes cease to be evolved. Wash dock glass into assay, add potassium chlorate, evaporate to dryness on a slow fire with the beaker uncovered. When no smell of chlorine or nitric acid is observed, remove and cool. Add 100 cc. boiling water, then 7 grm. ammonium chloride, W cc. ammonia (.880 sp. gr.), boil for five minutes, filter, wash...

Jan 1, 1911

By J A. Shonhardt, I Porter

All types of coal are liable to spontaneous combustion to a variable degree according to the inherent characteristics of the coal and also extrinsic factors. In order to successfully extract coal from highly capital-intensive longwall mining operations it is necessary to evaluate and manage any risks that may be present due to spontaneous combustion. A spontaneous combustion risk management plan for longwall mining is described in this paper. This risk management system comprises identification of conditions promoting spontaneous combustion risk, a laboratory or empirical risk classification system, determination of gas ladder, adoption of adequate ventilation plans and gas monitoring systems that will lead to the development of the spontaneous combustion action plan. The risk management system was applied to a greenfield site in NSW in 1992 when prediction of a high-risk category for the coal seam was made. After commencement of production a spontaneous heating problem emerged as predicted. Description of the case history of spontaneous combustion risk management for a longwall operation in this coal seam is included in this paper.

Jan 1, 2003

By M Fylak, R Wenda

Advanced preparation techniques open new ways for SEM and X-ray diffraction (XRD) investigations on hydrating cementitious systems. In this paper the early time hydration of Portland cement is studied with advanced cryo scanning electron microscopy techniques in combination with in situ X-ray diffraction and heat-flow calorimetry. The application of preparation techniques and analytical methods to Portland cement hydration are presented and discussed. Some aspects of hydration reactions are focused. The reaction products of the first minutes, changes in ettringite morphology, AFm formation during the deceleration period and the visualisation of C-S-H microstructures were special points of interest. X-ray diffraction analyses and Cryo-SEM images gave essential information about phase development, reaction kinetics, microstructure and morphology of hydration products. Portlandite, AFt and AFm phases were detected by in situ XRD. Cryo-SEM analyses enabled high resolution imaging and EDX-analyses of cement particles and reaction products. The results of the different analytical methods were compared to obtain detailed information about crystallisation processes and microstructural development during the first three days of Portland cement hydration.

Jan 1, 2008

It is now 32 years since Walsh's classic publication (1) heralded the beginning of atomic absorption spectrophotometry (AA) as we know it today. During this time, AA has developed into the most widely used analytical techniques for the determination of the metallic elements. The years have seen progressive changes in instrumentation so that today it is a highly sophisticated technique. One area of development in AA that is experiencing renewed attention is in the area of electrothermal excitation. In this technique a flame is not used by the analyte solution is atomised by an electrically heated graphite furnace. For a large number of elements the graphite furnace atomic absorption spectrophotometer (GFAA) is considerably more sensitive than flame work. It is common to be able to detect concentrations one hundred times smaller than those possible by flame. Today's geochemists are finding that they can gain valuable information out of very low limits of detection. Electrothermal atomic absorption spectrophotometry (or GFAA) allows for low limits of detection and can be seen to be a valuable aid to geochemical prospecting Analysis.

Jan 1, 1987

By Morrison AL

The volume changes occurring during the reduction by hydrogen of single, high-grade hematite pellets under isothermal and non- isothermal conditions were investigated using a time-lapse photographic technique. The major cause of swelling during iso- thermal reduction at temperatures in the range 600-1000¦C, was the disruptive stresses set up during the transformation of hematite to mag- netite. The severity of the disruption was temperature dependent; the degree of swelling increased with increases in the reduction temp erature. Under non-isothermal reduction conditions, in which the pellet temperatures were increased at constant heating rates over the temperature range 500-1000¦C, minor swelling (6-8%) occurred in the initial stages of reduction followed by pellet contractions of up to 15% in the final reduction stages. The low initial swelling and high final pellet shrinkages were due to a com- bination of the temperature dependence of the swelling mechanism, and the sintering of fine pores in the reduced iron in the latter stages of reduction at higher temperatures.

Jan 1, 1980

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

The combustion characteristics of Australian coals which contain high inertinite have been studied in a laboratory drop tube furnace and a Thermogravimetric Analyser. The pyrolysis chars and combustion residues were microscopically characterised using a modified coal petrography technique. Results indicated that the overall burnout of inertinite-rich Australian coals under pulverised fuel combustion conditions could be generally within a range of 97 - 99 per cent burnout. The studies showed that poor coal burnout cannot be generally related to high inertinite content in the Australian coals. The extent of coal burnout varies from coal to coal and vitrinite as well as inertinite may contribute to the unbumt chars in combustion residues. Combustion conditions had greater influence over char formation and coal burnout than the coal properties. However, under similar pf combustion conditions, coal rank and coal maceral composition had a strong influence over the coal combustion behaviours and final coal burnout. Simple correlations using coal properties may be used but with caution to determine coal volatile release and burnout at high temperature and rapid heating conditions.

Jan 1, 1991

Production of refined zinc (99.95 per cent) at the minesite without increasing greenhouse gas emissions is considered. As an example, exploitation of the full reserve of the McArthur River orebody is proposed, using the existing concentrator, whilst introducing radically innovative smelting technology. Bulk flotation of all the sulphide minerals is followed by smelting in a melt circulation reactor with tonnage oxygen. By smelting the high-energy pyritic concentrate and reacting the evolved sulphur dioxide with near-mine dolomite, a large amount of electricity can be generated. This is enough to supply all the requirements for the smelter itself, an air separation plant and a facility for compressing and liquefying carbon dioxide. Carbon dioxide is disposed of off-shore for enhanced oil recovery or by other means. The reacted dolomite fixes sulphur as an inert and environmentally acceptable solid residue. Treatment by these means leads to virtually zero gas emission smelting. The paper concludes with a vision for the future in which expansion of zinc smelting capacity is seen to be definitely needed.

Jan 1, 1998

By R H. Eric

Surface wave formation induced by a high-strength submerged jet in a bottom blown metallurgical vessels has been studied experimentally by using one-seventh water model of CLU (Creusot-Loire Uddeholm) reactor with two different tuyere configurations. Experimental results have been discussed in terms of the wave period, wave frequency and wave amplitude with respect to air injection rate and tuyere configuration at a 0.23 m bath height. The results from high speed photography observations displayed the formation of rotating surface waves which circulates within the water model. It was found that the frequency and the amplitude increased with gas injection rate. The wave period for off-centre nozzle orientation was found to be lower than those of the centre configuration. The experimental results also showed that the frequency of a rotating wave increases when the tuyere orientation becomes off-centred . The predicted amplitudes were in very good agreement with the experimental values over a range of gas flowrates between 0.00599m 3/s to 0.01081 m 3/s.

Jan 1, 2000

By P D. Fraser

This paper examines the new water-hydraulic (hydro powered) drill rigs that have been developed and proven in the last decade primarily in tabular, shallow-dipping, narrow-reef, hard-rock South African mines. These include - drill rigs for flat end tunnel development, narrow inclined raises and winzes, large inclines and declines and long hole based developments such as orepasses and vent raises. The hydropower technology rigs offer advantages both in safety and performance over traditional compressed air powered, hand-held development are generally more cost effective than imported oil electro-hydraulic drill rigs. Furthermore, hydro powered rigs are inherently energy efficient. The benefits of hydropower are discussed and a æcomprehensive development modelÆ is presented which demonstrates that orebodies can be accessed in significantly shorter times. æLocalisedÆ half level hydropower systems are introduced and a range of ancillary equipment available is listed.CITATION:Fraser, P D, 2012. The use of high-pressure, water-hydraulic (hydropower) technology in South African narrow-reef, hard-rock mines, in Proceedings Narrow Vein Mining 2012 , pp 229-236 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Mar 26, 2012

By Eaton R. A

The design of most underground mining machines shows little evidence of regard for ergonomic principles and operator comfort. Likewise, efficiency and ease of operation often appear to have been given little consideration in machines where ruggedness and simplicity have tended to dictate the configuration. Improvements in productivity are amongst the benefits to be gained by a different approach to machine design. The paper describes the philosophy and features of a test bed Load-Haul-Dump Vehicle undergoing trials at Mount Isa Mines. This machine is the outcome of a Research and Development Programme conducted by the Department of Mechanical Engineering at the University of Queensland and Mount Isa Mines Limited. The diesel powered test bed features an enclosed, air conditioned cabin, with a suspended operator's control station and electrically operated controls. An electronically controlled hydrostatic transmission incorporating wheel slip control, is another innovation. The performance and operator acceptance of the machine has led to adoption of most of the concepts in a new machine now being put into production.

Jan 1, 1987

There is no other effective way for study ing firedamp and coaldust explosions than to produce controlled explosions in a pre-monitor- ed environment - either mine openings kept for the purpose, or special surface galleries. Such explosion testing facilities have been employed historically at Buxton in U.K., with lesser known installations at Bruceton, U.S.A., Tremonia, West Germany, Katowice-Mikolow, Poland and elsewhere. Both firedamp and coal dust explosions are studied. Normally coal dust explosions are initiated by somewhat standardised methane air mixtures, by explosives, or purely by coal dust. Various structures and suppression installations are installed in roadways and galleries prior to explosion to simulate destruction and suppression, and the results of such tests form the basis of suppression installations, especially stone dust barriers and water barriers. Other data collected from these experiments include rev- ersals of explosion waves, pressures and temperatures and duration of explosion waves, analyses of aftergases etc. Other uses of explosion testing galleries include testing of explosives, electrical equipment and frictional . sparking.

Jan 1, 1981

By Nilsson C

Man has always been and will always be part of his environment, in ,a good, bad or indifferent manner. Until quite recently, this environment has been the atmospheric boundary layer above the land masses, and to a limited extent the air-sea interface of the oceans. Since the days when he lived in caves, he has built up a wealth of observations on these two environments,-with ever-increasing scientific precision which unfortunately until quite recently was completely insufficient for modern capabilities of data analysis. Consequently, in a sense, he has left in his wake thousands of years of missed, opportunities for making exact observations and increasing his understanding. The data of the past are lost and he has to be satisfied with what he can assemble from now on when his environ- ment, largely as a result of his actions, is exhibiting more and more rapid variations in time; in other words, time series of observations of phenomena are required, the length of which is critical for most purposes of analysis.

Jan 1, 1970