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By S K. Michelic, N Preisser

For certain applications, steels have to feature a very distinct and well-defined level of cleanness in terms of the number and composition of non-metallic inclusions. Therefore, one crucial aspect of steelmaking is removing and controlling said non-metallic inclusions during the process. Particle removal during ladle refining comprises three stages, namely: 1. Flotation 2. Transport through the steel/slag interface 3. Dissolution of the particle in the slag. Only if all three stages are completed the particle can be considered as fully removed from the steel melt which, in turn, leads to the slag being one of the most influential parameters for inclusion removal and control. Depending on the composition of the particles and the slag, the dissolution can be controlled by different mechanisms. This study focuses on the diffusion-controlled dissolution of solid oxidic particles in slags. For this, a model of particle dissolution has been developed. For modelling diffusion, either the differential equation following Fick’s second law can be solved, or an analytical solution to this equation valid for stationary interfaces can be used. Both approaches allow for calculations of concentration profiles of the dissolving species in surrounding slag. From this, the mass flux can be derived, which finally leads to calculating the boundary layer velocity due to considerations of mass balance. In this work, both methods as well as results of dissolution experiments using High Temperature Confocal Scanning Laser Microscopy are compared. This research aims to provide a framework for diffusion-based dissolution modelling in further expanding the understanding of particle dissolution in secondary metallurgy.

Aug 21, 2024

By H Zhang, Y Wang, S Sukenaga, H W. Ni, H Shibata, W Z. Mu

The crystallisation behaviour of low melting point CaO-SiO2-Al2O3-MgO inclusions greatly affect the deformability of inclusions during the rolling process. The crystallisation characteristics of CaO-SiO2- Al2O3-MgO melts representing the oxide inclusions in Si-Mn killed steel were systematically investigated. The effect of Al2O3 and MgO contents on the crystallisation change were analysed under a fixed CaO/SiO2 in the complex inclusions. The continuous-cooling-transformation (CCT) and time-temperature-transformation (TTT) experiments were conducted. The results showed that the increase of MgO content increases the crystallisation ability of CaO-SiO2-Al2O3-MgO inclusions, while the increase of Al2O3 content has the opposite effect. The viscosity, liquidus temperature of oxide melt and also the initial crystallisation potential might be the reasons for the change in crystallisation behaviour. Also, the crystallisation activation energy could semi-quantitatively characterise the crystal growth during the crystallisation of inclusions. To obtain low melting point plasticized CaO-SiO2-Al2O3-MgO (CaO/SiO2=1) system inclusions, the Al2O3 content of the system needs to be controlled larger than 15 wt per cent and the MgO content should be kept at a small amount.

Aug 21, 2024

The mineral pulp as it passes through grinding-classification, flotation and solid-liquid separation is examined in the context of it being a particulate fluid. By focussing on the complex viscosity and yield stress of the fluid, new control strategies are discussed. The mineral-particulate fluid is dominatred by non-Newtonian rheology (ie shear thinning, shear thickening, shear yield stress and compressive yield strength). The control of this Theology is seen to be dependent on the fundamental practice-particle interaction forces and with adequate information, it is possible to use the complex shear properties to advantage. The advantages, in terms of final waste and concentrate management, to high weight per cent solids in the mineral particulate fluid, are explored and control strategies outlined.

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

The HYC mineral deposit at McArthur River is about 1.5 kilometres long by 1.0 kilometres wide and 55 metres thick, and contains 227 000 000 tonnes of ore of average grade 9.2% Zn, 4.1% Pb and 41 g/t Ag. Major studies have been carried out continuously since 1955 over the deposit and in the general region. This work is continuing. A small underground mine was developed by driving a decline tunnel to intersect the mineralization 80m below the surface. This provided a fully representative sample of the total deposit unaffected by weathering or oxidation, and was available for the major test program carried out in a pilot plant built to determine the full metallurgical charac- teristics of the ore. The pilot plant operations followed investigations by research institutions, both in Australia and overseas, into the problems of this ultra-fine grained ore. The ultra-fine grained nature of the ore required grinding to an average size of 95% passing 37 micro metres or 400 Tyler mesh. A major feasibility and environmental report was submitted to the government covering all aspects of a development program. The geological, engineering, metal- lurgical, economic, cultural and environmental submissions contained in this report were studied by external consult- ants employed by the government, who agreed with the conclusions that the McArthur HYC deposit is at present Uneconomic.

Jan 1, 1984

By Phillips RN

Semi-confined, trachy-andesite sills which overlie the German Creek Seam, within the critical tensile strain zone, form major groundwater hazards to longwall mining at the German Creek underground mines. The water contained in these aquifers is normally neutral, but highly saline. Techniques used to detect aquifers include routine air-lift pumping in exploratory drill holes, downhole geophysical and geological logging and upstage packer testing. Hydraulic constants are calculated from pump-out and pump-in test results. Hydraulic parameters for the calculation of mine inflow rates are determined from pump-out test results because these tests appear to be more representative of aquifer drainage during goat dewatering than pump- in testing. During mining of the first longwall block at Central Colliery, caving fractures intersected overlying aquifers after the longwall had retreated 40m, and mine water inflow rate rapidly increased from less than one litre/sec to 25 litres/sec. The amount of water pumped out of the mine during first panel extraction was 140 megalitres with drawdown occurring over an area of 168 hectares. In the Southern Colliery area approximately 324 megalitres of highly saline water which is actively stored in the Aquila Sill area will be pre-drained from six well points prior to longwall mining. With effective pre-drainage from surface drill holes, maximum inflow rate into the mine during initial goafing can be reduced from 165 litres/sec to about 45 litres/sec.

Jan 1, 1988

Using normal low pressure filtration methods for the dewatering of fine china clays, the best that can be achieved is cakes with about 30% moisture. In order to get the moisture levels down to acceptable levels the traditional method used is thermal drying, which is both costly and dust creating. It was to improve this process that ECC International embarked upon a programme of development of filtration equipment using high pressure to achieve significantly lower moisture levels. This development work investigated several design philosophies and culminated in the production of two quite different solutions. The High Pressure Plate Press uses round plates / chambers of one metre diameter and a filtration pressure of 70 bar. This press is fully automatic and produces a surface dry cake that has sufficient plasticity for the further processing that is required on specific qualities of china clay. The TUBE PRESS on the other hand uses a unique design configuration and operates at a filtration pressure of 100 or 140 bar, depending upon the model. The TUBE PRESS produces a brittle, surface dry cake that is easy to handle and a filtrate that is usually crystal clear. The TUBE PRESS achieves a much higher degree of separation than is possible with conventional equipment, which is particularly important if the filtrate is the product. Over the past 15 years plants incorporating both HP Plate Presses and TUBE PRESSES have been installed in the china clay operations of ECC International and are giving excellent trouble free service. The TUBE PRESS has also proved to be extremely versatile, effectively dewatering a wide range of fine particled slurries, in a number of diverse industries.

Jan 1, 1989

By J Moncrieff, P Bellairs

The Black Star Open Cut is located immediately adjacent to the township of Mt Isa and is situated in the middle of extensive pre-existing infrastructure including two concentrators, two smelters, a wet fill plant and two shafts. At any one time there are in excess of 500 people working on the surface within an industry-accepted 600 m exclusion zone from Black Star blasts. Apart from the surface operations there are also the underground operations including the lead mine (closed in December 2005) and the Enterprise and X-41 mines that must clear for all Black Star blasts. The application of industry standard blasting exclusion zones (600 m) was risk assessed as imposing operationally prohibitive constraints which could cause significant business interruption due to the logistical challenges required to ensure that all personnel from surface plants were evacuated for each blast and potential for lost production whilst these personnel were not operating the plant. In was therefore an imperative for the blast exclusion zone to be reduced. This was achieved by the: use of a QA/QC team to ensure that relevant drill and blast implementation is within an acceptable tolerance (KPIs) from design; use of high-quality stemming material called HMR, which is a by- product of the concentrating process and is generally sized at -14 mm with very little fines; implementation of appropriate training and support to Black StarÆs own blast crews, reinforcing the need to achieve the designed amount of stemming in every hole; and provision of appropriate support from Black StarÆs management for additional resources to ensure that every blast achieves design within the KPIs but especially in high-risk areas. The blast exclusion zone was successfully reduced after monitoring the flyrock results from more than 176 blasts. Black Star Open Cut now maintains a minimum blast exclusion of 200 m in critical areas; however, general blasting currently uses a 250 m exclusion as this provides additional risk management whilst still minimising the logistics associated with clearing and securing the slightly increased area.

Jan 1, 2007

By Koppe J. C, Dimitrakopoulos R, Costa J. F

Grade control and the delineation of ore/waste in open pit operations is traditionally based on the comparison of estimated grades with an economic cut-off. This paper deals with an alternative approach to grade control based on estimating gra

Jan 1, 1998

The paper is aimed at mining engineers and other mining practitioners in the metalliferous mining industry who are considering the use of roadheaders and wish to understand the basic geomechanical and operational principles controlling their performance. The paper aims to address metalliferous minersÆ general unfamiliarity with roadheader technology, which is one of the factors which has limited the application of these machines in such mines. The historical development of drag tool mechanical excavation machines is briefly discussed, and factors affecting the application of roadheaders are mentioned. The mechanics of cutting with drag tools is then reviewed as are the effects of these and tool wear on tool performance. The implications of tool performance to roadheader performance are mentioned, the potential benefits of high pressure waterjet assistance are discussed and the relative performances of different tool types and materials are compared. Roadheader performance factors including productivity and utilisation are mentioned, and the state-of-the-art of conventional roadheaders is discussed in the context of machine weight, power and cutting head configuration. The influence of these and rock strength on machine productivity is analysed. Alternative, developing technologies are discussed which may extend the effective use of mechanical excavation into stronger rock masses which are beyond the range of conventional roadheaders. Finally, conclusions on these discussions are presented, along with recommendations for continuing research and development.

Jan 1, 1997

By Ward S. C, Gardner J. H

In 1990, Alcoa of Australia Limited was elected to the Global 500 Roll of Honour of the United Nations Environment Program for the environmental management and rehabilitation of the bauxite mines in Western Australia. This award placed Alcoa in the international best practice category. The story of constant improvement spans more than 20 years from a 'trial and error' start to a strategically focussed and research driven program today. The main driving force has come from within the company, against a set of strong corporate values and a well publicised Vision based on 'excellence through quality'. Along the way public opinion, action group protests, increased legislative controls together with the professional competence of internal and external environmental resources have all played a part in arriving at the level of current environmental management and mine rehabilitation performance. There were numerous lessons learned here during the evolution and maintenance of best practice. These included: I . To work diligently in obtaining a vision or strategic intent on mine site rehabilitation and environmental management - don't be easily dissuaded.

Jan 1, 1995

By A W. Bewsher, T C. McCu, D B. Mapleson

The Miitel nickel sulfide deposit has been overprinted by a family of late stage structures that have acted as conduits for fluids that have contaminated the orebody with arsenic minerals. This has resulted in highly variable and unpredictable arsenic grades throughout the Miitel orebody. The ore produced from Miitel is processed under a toll-treatment agreement with Western Mining Resources Kambalda Nickel Concentrator. Part of this arrangement includes a financial penalty if monthly average arsenic grades in ore delivered exceed 800 ppm. This constraint has provided an extra challenge to the Miitel mine geologist in addition to daily underground duties. Routine development and stope mapping, close spaced sampling and cross-sectional interpretation were used in building an understanding of the structural controls of arsenic mineralisation and ore repetition at the Miitel nickel mine, and in providing maximum input to mine planning and scheduling. The distribution of structures responsible for arsenic introduction is now well understood from detailed mapping, sampling, and interpretation. By applying these insights to mine scheduling, the operation has successfully managed arsenic levels within the required specifications. Geological mapping has also improved the understanding of the structural complexity of the ore deposit, leading to the addition of ore tonnes and an increased confidence in resource modelling. Regular sampling and tight controls on data quality provided confidence in a strongly skewed arsenic data set. Multiple Indicator Kriging has been used for resource estimation of the arsenic contaminated nickel ore since it allows explicit control of the spatial influence of extreme grades in the positively skewed arsenic sample population. Both the grade control and exploration data sets are used to model the arsenic distribution.

Jan 1, 2003

By Henley R, Harris L

High resolution airborne magnetic and radiometric data have been shown to optimize exploration for epithermal gold deposits in the vicinity of Charters Towers, northeastern Queensland. The radiometric data allow extrapolation of poorly outcropping geology to provide a cost-effective mapping technique, even at exploration scales (eg. 1:25,000). At a regional scale (eg. 1:100,000) the magnetic data reflect the regional tectonics and divide the area into domains for the application of different genetic models. For example: 1. the Ravenswood Batholith is characterized by multiple intrusions dating from Ordovician to Permian age. The polarity of the magnetic anomalies implies an age for the intrusions and indicates a deposit style for exploration. 2. extensional and wrench tectonics along the northern margin of the Drummond Basin are interpreted from the magnetic data and indicate favourable blocks for detailed exploration. Genetic exploration models may be tested in favourable environments by the recognition of geophysical signatures. These signatures reflect structural, lithological and alteration patterns arising from controls on ore deposits and can be applied at regional or detailed scales.

Jan 1, 1989

By M Titley, E Maidens

Many gold deposits were mineralised by fluids and processes that also altered the host rocks. This alteration may often be a useful visual aid that distinguishes barren, low-grade from high-grade regions in a rock mass. Alteration intensity is commonly used in gold deposits as a visual tool, along with face sampling or grade control support, to define oreblocks and guide excavation in underground and open pit mining. However, alteration is not often used at the resource estimation stage. Mineralised lodes are usually defined by geologists using a ægeo-grade envelopeÆ, where a number of constraints are considered, including an (arbitrary) cut-off grade; the ænaturalÆ grade break between high- and low-grades; and geological features including structural, lithological or alteration continuity. The geo-grade envelope is usually thought to satisfy the requirements of stationarity for grade estimation, and is considered a single domain. This paper examines a modelling technique combining gold grade and alteration, applied to the Wallaby deposit in Western Australia, to imbue a greater level of detail to the grade estimation in a region tested by relatively sparse drilling. This was achieved by utilising the correlation of gold grade and alteration, along with the spatial characteristics of the alteration, when estimating grades within a number of lodes. The alteration-driven estimation was utilised in conjunction with an unfolding approach, and the use of probability estimates, to overcome geometric data constraints. This technique allows greater control and most likely provides a more reliable estimate of the mineable resources than a global grade cut-off when visual control is to be a major vector in grade control.

Jan 1, 2003

By Beech-Jones J. M

At Port Latta in Tasmania, Savage River Mines operates vertical shaft furnaces for the firing of pelletised magnetite concentrates. At times the temperature profile of the furnace has changed markedly, necessitating the- burning of greater quantities of fuel to maintain good pellet quality. A study of the oxidati=of magnetite concentrates was under- taken because this exothermic process supplies much of the heat required to indurate the pellets. Using the thermal analyses methods, different magnetite concentrates from Australian and overseas were heated in air under identical conditions, to compare rates of oxygen uptake and of heat release. In addition, a compari- son was made of the oxidation behaviour of different particle size fractions of a selected concentrate. Particle size analyses, x-ray diffraction and dilatometer tests were used to aid inter pretation of the thermal analysis traces. The investigation emphasized the importance of particle size and ferrous iron content in determining' oxidation rates from the commencement of heating.

Jan 1, 1974

By Field R. V, Graieg O, George T. J

The design, construction and operation ofa laboratory scale rotary pot kiln are outlined. Charges ofup to 3 kg can be heated to temperatures up to 1200°C in a controlled atmosphere. Some examples of pyrometallurgical investigations carried out using the kiln are briefly described, including thermal reactivation ofcarbon using steam at 550-850°C, high temperature testing ofkiln liners for corrosion resistance to fluoride, and calcination oflimestone. Results obtained from these trials allow either direct scale-up to the Engineering Chemistry Laboratory's pilot-scale (50-100 kg/hr) rotary kiln or modifications to be made to commercial scale processes and/or equipment.

Jan 1, 1986

By Shuguang L, Jing S

Computer controlled truck dispatching systems is a newly-developed technical system in surface mines with shovel-truck technology. The real time dispatching criteria, as the core of optimal truck dispatching software, are analysed and a new criterion, complex dispatching criterion, is put forward. Dispatching criteria previously proposed include: 1. `Earliest Loading' (EL) - to assign a truck to the shovel at which the truck can be loaded earliest. 2. `Max Truck' (MT) - to assign a truck to the shovel at which the truck will have the shortest waiting time. 3. `Max Shovel' (MS) - to assign a truck to the shovel which has been waiting for the longest time. 4. `Minimum Saturation Degree' (MSD) - to assign a truck to the shovel at the branch where the truck flow saturation degree is minimum. 5. `Minimum Saturation Degree with Truck Cycle time consideration' (MSDTC) - as the MSD principle, with the truck travel cycle also considered. 6. `Fixed Dispatching' (FIX) - to assign trucks to fixed shovels. A system simulation model has been set up for truck dispatching system analysis. A few surface coal mines have been selected for case studies. Equipment waiting times and shift production of the system are obtained as the main outputs of the model. Simulation results show that each dispatching criterion has its own applicable range, no one can absolutely dominate the others. For example, when under-trucked, EL and MT criterion can obtain higher production than the MS criterion; when over-trucked, it is vice versa; while for MSD criteria, better results can be obtained no matter how the truck numbers fluctuate. From the view point of shovel output balance, large fluctuations occur for EL and MT criteria, while a good balance can be obtained for other criteria. In the light of dynamic change of mining system conditions, a single dispatching criterion is not necessarily reasonable. A complex dispatching criterion has been put forward to seek the complex optimum effect. Taking the advantage of each dispatching criteria, the dispatching result of a complex dispatching criterion dominates over individual dispatching criterion and a comprehensive optimum effect can be reached.

Jan 1, 1995

By M Ljunggren, M Lundh

Dissolved air flotation (DAF) in wastewater treatment as a separation process of submillimetre biological flocs is based on the generation of bubble/floc aggregates. DAF is a complex process but has got advantages, such as allowing a high hydraulic load, compared to sedimentation. A thorough knowledge of the physics of the DAF process is, however, still lacking. This paper will present results of experimental studies on three aspects of significance to the separation process û the flow structure in the flotation tank, rise velocities of aggregates, influence of floc size on the separation efficiency. Flow structure. Measurements were performed in a pilot plant mapping and visualising the velocity field. The dispersion water (bubbles) had a decisive influence on the flow structure due to the effect of the bubbles on the bulk water density. Stratified conditions with a less dense, bubble-containing upper layer and a clear water, denser bottom layer were important for a good separation. A simple model of the stratified flow structure was elaborated making it possible to interpret the function of the aggregate rise velocities. Bubble/floc aggregates. The dynamics of single flocs, bubbles, aggregates were visualised using a borescope + CCD video camera + digital recorder + image analysis. Sequences of video frames made it possible to determine the rise velocities of the single aggregates. These velocities were found to be in the range 1 - 9 mm/s with a tendency for large flocs to have higher rise velocities. Separation versus floc size. The floc size distribution was measured in the DAF process. Data from three different DAF cases showed, that large flocs (> about 100 ¦m) were entirely separated, whereas small flocs experienced a less good separation. It was, moreover, found, that a very significant separation of flocs took place in the very upstream end of the separation zone in a pilot plant case.

Jan 1, 2005

By Grouhel P

Blasting performance is directly related to the characteristics and efficiency of the explosives used. The selection of the correct explosive for particular blast conditions and objectives depends on the ability to characterise the performance of individual explosive products. Techniques have been developed by the JKMRC to measure explosive performance and assess the impact of explosive performance on blast results. Studies conducted at a number of mine sites have shown that different types of explosives perform quite differently and that the performance of any particular explosive can vary significantly. The principal causes of these variations have been identified and detailed blast monitoring techniques, including the analysis of muckpile fragmentation and shape, have been used to quantify the effects of explosive performance on blast Results.

Jan 1, 1990

The Olympic Dam mining operation is some 520 kilometres NNW of Adelaide on the Roxby Downs Pastoral lease. The deposit containing copper, uranium, gold and silver was discovered in 1975 by Western Mining Corporation (WMC). A joint venture was formed in mid-1979 between WMC (51 per cent) and British Petroleum (BP, 49 per cent) for the development and exploitation of the deposit. WMC assumed 100 per cent ownership after acquiring BP's share in early-1993. Ore is won from a highly mechanised underground mining operation and processed to refined products. Current annual output from the mining of 3.0 Mt of ore is approximately 83 500 t of refined copper, 1400 t of uranium oxide, 750 kg of gold and 12 000 kg of silver. Conventional long hole, open stoping techniques are used to extract the production ore. Since stope production began in April 1988, full surveys and appraisals of stopes have been carried out to evaluate the integrity of the design and blasting techniques. This evaluation included the determination of the degree of dilution or non break that had occurred. Performance information also made it possible to re-design any adjacent stopes to retrieve remaining ore and conversely, avoid the chances of targeting backfilled material in the future. Performing stope surveys proved not only to be a time-consuming process but one fraught with access and line-of-sight problems. Occasionally it was not possible to obtain any stope survey data, and as was often the case with the mine pass system, rarely. In 1992 the sudden failure of the pillar between the fine ore and mullock passes and the subsequent delays to production, emphasised the need to effectively monitor pass wear. Initial information regarding the development of the Cavity Measurement System (CMS) prototype (Figure 1) indicated that it had the potential to solve these problems by the introduction of a remote scanning device into a cavity. Following a great deal of investigation, Olympic Dam Operations purchased the first CMS in Australia. This paper discusses its application for all underground void surveys and the procedures developed to manage both field and office requirements.

Jan 1, 1995