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By N Voller, A Ishmurzin, G Hackl, M Wu, A Kharicha, M Chintinne, C M. G Rodrigues, A Ludwig

Slag fuming (SF) is a critical process for recycling zinc-containing slags, but the corrosive nature of molten slag poses challenges to the reactor durability. The freeze-lining (FL) technique offers a solution by forming a protective layer on the reactor wall. It requires intensive cooling using watercooled jackets, which can stabilise the FL while compromising the energy efficiency of the process. This study presents a computational fluid dynamic (CFD)-based model to optimise the SF process by considering FL formation and its impact on heat transfer and reactor wall temperature. A volumeof- fluid (VOF) model is coupled with a mixture continuum (MC) solidification model to capture the intricate multiphase flow dynamics within the SF furnace. Two FL types are considered: FL solidifying on the reactor wall in the slag bath region; and FL solidifying on the reactor wall in the freeboard region. The FL of the first type forms when the slag temperature drops below liquidus temperature. The FL of the second type only forms when a splash-induced slag droplet collides with the freeboard wall and solidifies. A series of splashing events are necessary to coat the freeboard wall. The simulation was run until a global energy balance was reached. This means that the heat losses from the water-cooled jacket, bottom wall, outlet and fuming balance the heat gains from the hot gas injected through the submerged plasma torches. The increase in FL thickness, due to its low thermal conductivity, reduces the heat losses through the reactor walls. The calculated FL thickness and heat fluxes were in good agreement with industrial data, validating the model’s credibility. The simulation results provided valuable insights into the fuming process, including slag bath temperature evolution, slag splashing dynamics, FL formation patterns, local heat fluxes through the reactor wall and overall energy balance. These findings can inform process optimisation strategies to enhance the energy efficiency and sustainability of SF operations. The authors have built a prior version of the model framework and applied it to simulate FL formation in an electric smelting furnace (ESF). The results from both the ESF and the current SF highlight the applicability of such model framework to a range of industrial processes involving FL formation. This model framework can ultimately contribute to more energy-efficient and sustainable industrial operations.

Aug 21, 2024

Techniques and results achieved during the excavation of the Melbourne Underground Rail Loop (HURL) are summarised and discussed in the context of the various restraints present in a typical urban construction project. Mechanical methods (as distinct from those utilising blasting)accounted for the bulk of the excavation. Ground support was critical in this particular geological excavation setting, but is not discussed in detail except insofar as it constitutes a restraint to excavation progress.

Jan 1, 1978

By Braes J. R, Neale J. R

The New Broken Hill Consolidated Limited (NBHC) mine currently produces 1.42 million tonnes of silver, lead and zinc ore annually. All of this ore is treated by the NBHC milling ccx[plex. This paper describes the crushing, grinding, flotation and filtration circuits used in the treatment of this ore and lists the major items of equignent used in these circuits. Metallurgical results, manning levels and consumption rates of reagents and grinding media are shown.

Jan 1, 1983

By King ND

This paper presents an economic study comparing two gold recovery processes, zinc precipitation (Merrill-Crowe) and carbon-in-pulp (CIP). Capital, operating, and gold losses costs from an actual CIP plant study are compared to costs developed from a hypothetical Merrill-Crowe process flowsheet. ' Results indicate an overall economic advantage to CIP over Merrill-Crowe for plants processing slurries within the range of the five gold solution grades selected for this study.

Jan 1, 1982

Results from current NERDDC funded research into the geotechnology of highwall trench mining methods have clear implications for mine planners in the areas of blast design, trench shape, location of the surcharge spoil and remnant coal pillar design.Adoption of successful smooth wall blasting techniques not only removes safety hazards from the trench face, but limits development of bedding partings at the seam contacts that interrupt the smooth transition of stress across the coal seam.

Jan 1, 1992

An increase in the silver to gold ratio with increase in depth in the main ore shoot of the Crown-Crescent lode in the Emperor gold mine, Fiji, was found to be due mainly to vertical zoning of gold-silver tellurides. The zoning resulted from a two-stage sequence of ore mineralization.The application of some recent studies of the synthetic Au-Ag-Te system to natural gold-silver telluride assemblages is discussed.

Jan 1, 1971

In conjunction with a study on wear of drag bits the effect of clearance angle on penetration rate was studied.Increases in clearance angle from 24 1/2 up to 30° gave an increase in penetration rate. Thereafter the rate was apparently affected by partial clogging with cuttings.Analysis of results was by a linear regression model and the t-test was applied to assess the significance of parameters in the penetration equation.

Jan 1, 1969

By Gillies A. D S

The paper presents a review of research in the area of explosible coal dust with respect to safety in the underground mining environment. Research over the last several decades has concentrated on generating dust clouds in small scale laboratory explosion chambers to study flammability limits and the physical and chemical variables which affect explosion propensity. The validity of this approach is discussed and the results obtained for a range of coal types compared.

Jan 1, 1994

By S Arnold

Properties of the soil profile fundamentally control water-limited ecosystems. Soil water availability affects vegetation dynamics of plant communities, but is also affected by these communities in return. Understanding this eco-hydrological interplay and the role of physical soil restoration is crucial for successful rehabilitation and management of post-mining landscapes in semi-arid areas. However, uncertainties exist in both the mathematical description of plant communities within ecological submodels and the predictability of future rainfall events. This study uses information gap decision theory combined with an ecohydrological system model to investigate how both uncertainties impact decision-making in the context of ecosystem rehabilitation. A range of management strategies are investigated to identify the optimal soil thickness for successful rehabilitation of native plant communities in Central Queensland. The results emphasise that thicker soils can counterbalance uncertainty in mathematical description of plant communities by increasing the simulated survival probability of plant communities. However, the influence of thicker soils on the robustness of plant communities against a change in future rainfall amount is rather marginal. By allocating an economic value for restoring a particular thickness of soil layer, these results can be used to evaluate the costs of ecosystem re-establishment with regard to two target measures - the survival probability of the plant community and their robustness against climate change.CITATION:Arnold, S, 2012. Finding optimal soil restoration strategies in the face of uncertain future rainfall amount, in Proceedings Life-of-Mine 2012 , pp 91-96 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 10, 2012

By Atkinson D

This paper briefly outlines the develop ment of the froth flotation plant at Coal Cliff Colliery. The plant was superimposed onto the original flow sheet in which fines were merely thickened and filtered. Test work leading up to the installation is described and the final layout is discussed. Details of the concentrate and tailings systems are given. Preliminary results of a further extension involving the use of a Davcra flotation machine are also given.

Jan 1, 1974

By Blom W. M

Shareholders, creditors, government agencies and auditors all have a different perspective of financial reports which is determined by the uses to which they put the information disclosed in the report.Shareholders today are better informed than previously and are more aware of the market in which they are investing. This is the result of the increasing role of institutional investors and the increasing reliance being placed on analysts to interpret financial information.

Jan 1, 1990

By R C, K L. Rees, J S. J van Deventer

In contrast with previously published models for the carbon-in-pulp (CIP) process, the model proposed in this paper incorporates film transfer, intraparticle diffusion, simultaneous leaching, preg-robbing, the loading of multicomponent species, and the effects of fouling and changing cyanide levels. The rationale behind this comprehensive model is that changes in fouling and competitive adsorption along a CIP cascade affect the profiles of gold loading. As it is impossible to quantify all these non-ideal factors, a method is proposed whereby an imaginary species is postulated so as to combine all the competitive effects. A plant survey at the Telfer mine has shown that the mass loss due to a gravimetric analysis of the fouled carbon could be used directly to quantify this competitive effect. The degradation and consumption of cyanide along the Telfer CIP cascade enhance the loading of copper on to the carbon, which should be taken into account when modelling the gold profiles. It appeared that the effect of cyanide itself on the loading of gold was negligible compared with its effect on the copper. Evidently much more research is required on this topic in order to optimise CIP operations exposed to constantly changing conditions.

Jan 1, 1998

By M DellÆAmico, K Vining

The iron blast furnace is the most widely used and efficient producer of liquid iron; however, emissions from sintering and coking cause environmental pressure for the integrated steel works. The combustion of coke fines (breeze) during sintering contributes to greenhouse gases (GHG) (eg carbon dioxide) and is a source of SOx and NOx emissions. Coking capacity is also constrained by environmental concerns and economic factors, such as increased coke consumption, and short supply is leading to high prices. Improved coking practices, which result in reduced production of fines, are also contributing to the tight availability of breeze for sintering. This combination of factors presents an opportunity to consider alternatives to coke as a fuel for sintering. CSIRO Minerals has been investigating the use of wood biomass/char as a substitute for coke during sintering. Wood biomass, or char produced from it, is an attractive carbon source as carbon dioxide liberated during combustion can be sequestered back into growing biomass. It has great potential to reduce the emissions from integrated steelworks and improve their environmental acceptability. Harvested biomass/char is also a renewable and sustainable resource and can be integrated with good land management practices such as remediation of salinity affected land. Weeds, especially woody weeds, can also be used as a source of biomass for charcoal, and integrating char production with weed management can help address a pressing environmental issue in Australia. Previous reported preliminary testwork indicated that the use of Red Gum char as a replacement for coke resulted in a product sinter of comparable quality, improvements in productivity and significant reductions in SOx and NOx emissions. In the latest testwork, CSIRO has examined the properties of a range of potential charcoals, and has conducted a further series of granulation and small-scale sintering trials with them in simulated Japanese Steel Mill iron ore blends. Sinter fuels characterised and evaluated include industry sourced coke breeze, commercially available wood char and a charcoal from prickly acacia (acacia nilotica). Prickly acacia has been declared a noxious weed, is widespread in Australia, and is classified as a æWeed of National SignificanceÆ. The results presented in this paper support the notion that charcoal outperforms coke in many aspects of iron ore sintering and factoring in environmental considerations makes the switch to charcoal even more favourable.

Jan 1, 2005

By R M. Smart, A T. Harrison

Backfill systems using unconventional cementitious binders have been successfully used in relatively deep and hard rock tabular mines for longwall, scattered stoping and shaft pillar removals. Two unconventional cementitious systems are discussed: A ground granulated blast furnace slag (GGBS) with an activator containing lime. This has been used with a total tailings æstableÆ slurry at a relatively low dosage of less than seven per cent, by mass, based on dry solids. The room and pillar stopes supported with this fill were up to 20 m high and the tailings were relatively high in pyrite. A GGBS binder plus a silicate based activator and gelling agent that virtually eliminated all water drainage (and hence post filling shrinkage). The system used a slurry, but the addition of the activator created a final placed product that had the behaviour of a paste. The system has been successfully used for almost ten years in the following applications: stoping widths (mining heights) above 1.6 m; and shaft pillar removals in seismically active areas at the end of the life of the shafts. This paper discusses the technical merits and costs of the systems and compares them to other fill systems (including true paste systems). the acceleration (normally g, 9.81m/sec2) is increased to a significantly larger (but generally unmeasured and unknown) value, as shown in Figure 1.

Jan 1, 1998

By S H. Li, H Z. Gu, A Huang

High aluminium steel is a promising advanced steel known for its exception properties and holds significant economic and strategic importance. However, the CaO-Al2O3-SiO2 based slag with high alumina content reacts vigorously with alumina refractories during the smelting process at high temperature, seriously affecting the safe and efficient production of furnaces and resulting in the formation of Al2O3-MgO non-metallic inclusions within the molten steel. This is a bottleneck problem for high-quality steel refining, and the key reaction path during the corrosion remains unclear. The dissolution reaction mechanism of alumina refractories in high alumina CaO-Al2O3-SiO2 slags under a weak static magnetic field was investigated in this work, using high temperature laser confocal microscopy and in situ radiation spectroscopy techniques. The results indicate that the interaction between the high alumina slags and the alumina refractories is governed by free radical reactions. The dissolution of alumina forms AlO and AlO2 radicals. The reaction rate increases with the C/S ratio of the slag due to its low polymerisation. The reaction between non-bridging oxygen and AlO2 free radicals accelerates the generation of AlO and O2ꞏ- radicals. The reaction layer composed of calcium aluminate is formed through the recombination of AlO, Caꞏ+ and O2ꞏ- radicals. The weak static magnetic field induces the Zeeman splitting of free radical pairs and intersystem crossing occurs, promoting the formation of triplet free radical pairs through the hyper-fine coupling effect. The reaction can be significantly inhibited as the triplet free radical pair does not meet Pauli’s incompatibility principle. This discovery perfects the structure theory of molten slags with radicals and provides supplement to the design of the highly slag-resistant refractories, and provides the theoretical basis for the development of external field protection technologies for high-quality steel refining.

Jun 19, 2024

By F Pavloudakis

The installation of on-line analysis systems in the open-pit mines of the Public Power Corporation SA (PPC, the state-owned electricity entity of Greece) is considered to be the key-parameter for performing improved quality control and blending/homogenisation of the produced lignite. In order to investigate the accuracy of these systems under the site-specific conditions of the Greek lignite deposits, a research project was carried out. This was necessary since there is lack of experience in using on-line analysers in mines that produce a fuel of such a poor and largely fluctuating quality. After thorough market research, a dual energy gamma ray transmission on-line ash analyser was installed in Kardia mine of Ptolemais û Amynteon Lignite Centre, which is located in West Macedonia, Greece. The initial results obtained after the realisation of a series of dual-comparison trials (ie using two series of reference values that allow three-way comparisons) pointed out several problems that obstacle the achievement of high accuracy on-line measurements. More specifically, the measurements obtained by the analyser were higher than the concentrations determined by the two laboratories when the ash content was lower than 12 per cent (in wet basis). On the contrary, when the ash content was higher than 12 per cent, the measurements of the on-line analyser were lower than the concentrations determined by the laboratories. In other words, the range of the measurements obtained by the analyser was narrower than that corresponding to the lab analyses results. Therefore, the use of this on-line analysis system under the site-specific operating conditions of Kardia mine does not guarantee improved quality control of the lignite fed to the mine-mouth located power plant. Most probable reasons that explain the above-mentioned problems are the following: The frequent and widely ranging fluctuations of the chemical and mineralogical composition of the lignite transported by the conveyor belt, especially as far as its calcium content is concerned. This result from the nature and the origin of the mineral matter co-excavated with the lignite, which varies from calcareous marls to sands and clays rich in aluminium and silica minerals. The fluctuations of the lignite quantity transported by the conveyor belt. The change of the linear concentration of iron contained in the fabric of different belt parts.

Jan 1, 2003

By K Koskinen, S Ronkainen

The flow field induced in an Outokumpu TankCell and by an OK rotor-stator mixing device in a laboratory and a process size flotation cell was modelled numerically using computational fluid dynamics (CFD). The primary target was to discover and reproduce the various interactions between the flow field and the flotation cell by numerical means. As power consumption depends sensitively on flow field, it can be regarded as a top-level derived quantity (or measure/metric) indicating the validity of the numerically obtained flow field. Having properly validated numerical means to produce the flow field the influence of various design parameters can be captured with certain accuracy. In addition, separate gas and solid phase models for bubbles and solids, respectively, were implemented. The comparisons between velocities and turbulence quantities measured using the laser doppler velocimetry (LDV) technique and CFD modelling were performed. The grid generation was performed with the commercial Gambit 1.3 and the subsequent integration and solving of the resulting algebraic equations with the commercial CFD-code Fluent 6.22. The computationally economic multiple reference frame method was included to model the moving rotor blades. Gas and solid phase models were modified mixture models.

Jan 1, 2005

By L Yang, L Chen, E Hu, D Tang

Online monitoring of particles cumulative percent passing (PCPP) for a target size at hydrocyclone overflow, compared with traditional offline methods, provides PCPP feedback in real time, and is advantageous in enabling energy-efficient comminution, increasing downstream flotation efficiency, and improving upstream resource knowledge. However, existing online approaches are generally costly and bespoke, and some are sensitive to operational changes. Therefore, this study proposes a new low-cost alternative based on accelerometer measurement for online PCPP monitoring in the overflow of hydrocyclones and provides a preliminary experimental investigation under dry condition. The proposed method uses a sensing probe inserted into the overflow pipe of a hydrocyclone to receive particle impact from the incoming slurry, with accelerometers attached to the probe and mounting frame outside the pipe for particle-probe impact detection. As a preliminary investigation before studying particle-probe impact events in slurry, tests under dry condition without fluids were conducted using dry sand particles in free fall from a fixed height. Accelerometer measurements are analysed in both time and frequency domains through root-mean-square (RMS) and fast Fourier transform (FFT). Results show that accelerometer measurements are useful in estimating mass flow rates, which are correlated to the accelerometer output amplitude RMS values in time domain, in a non-linear mapping. Different particle size classes can be identified by examining the accelerometer output amplitude at a known mass flow rate. Different particle size classes feature their distinct signature frequencies (SFs) that can be examined via FFT and the SF is found to be independent of the mass flow rate. The results imply that any PCPP changes can be detected by the change in the accelerometer output amplitude as well as a shift in SF, which demonstrates the effectiveness of using accelerometers to gauge changes in PCPP. Based on the current findings in dry condition, future work will investigate particle-probe impact events in slurry.

Aug 24, 2022

By M McDonald

KiwiRail has a goal of significantly improving passenger rail services to west Auckland, as part of its DART (Developing Auckland’s Rail Transport) suite of projects. The New Lynn Rail Trench (NLRT) project was a significant component of this work. The NLRT project facilitates essential doubletracking of the Western Auckland line, and provides a new commuter transportation hub within a busy town centre.The 1.5 km stretch of track through the New Lynn town centre has bisected the township for over 80 years. Double-tracking the line provided the opportunity to grade-separate road and rail, which would help to re-connect both sides of the township and enhance public amenity and safety.KiwiRail employed an Early Contractor Involvement (ECI) procurement model engaging a consortium comprising Fletcher Construction, Beca Infrastructure and Synergine to develop a Design and Construct solution.With weak soil conditions and high groundwater levels, a diaphragm wall construction method to form the trench walls was selected as the best solution. Further challenges to construction included working within a narrow rail corridor constrained by buildings along much of the boundary, and a requirement to keep the existing line open for rail services. Detailed construction planning was required to ensure rail and construction safety in a constrained space whilst building the trench walls, propping these walls during excavation, and constructing the base slab in the most efficient way possible.This paper will detail the geotechnical conditions and the additional constraints that made this rail trench a challenging structure to design. It will also describe the fi nal design and construction methodologies that were employed, that allowed very successful completion of the project.Additionally, this paper will review the design and construction lessons applicable to the current Victoria Park Tunnel project, and indeed for all future cut and cover tunnel projects in the Auckland isthmus.

Mar 8, 2011

By S K. Michelic, M Schickbichler, A Kharicha, E Karimi-Sibaki

The requirements for the controllability of metallurgical processes are increasingly becoming the focus of both industry and research. Advances in this field of research not only impact the stability of processes but often also influence the quality of the final product. One important way to examine processes in-depth, and thus show potential for improvement, is to describe them using physicsdriven models. In metallurgy, thermodynamic and kinetic descriptions of interactions between individual components of a system are often used to describe and analyse important metallurgical phenomena across the entire process. However, for the creation of physics-based models, boundary conditions and process variables must be implemented to enable a description that is as realistic as possible. The collection and generalisation of boundary conditions and process variables is, therefore, an important step towards functional models. The focus of this study is the determination of mass transfer coefficients between all components in a steel/slag/refractory system. For this purpose, experimental and theoretical methods are applied. Laboratory scale experiments are carried out in an induction furnace, and the mass transfer coefficients of the defined steel/slag/refractory system are calculated from changes in the chemical composition of the various components. Additionally, a calculation of the mass transfer coefficients based on dimensionless quantities is carried out. By comparing the values of the mass transfer coefficients determined theoretically and those determined experimentally in the trials, the suitability of the calculation is examined. The collection of mass transfer coefficients provides essential findings for future kinetic descriptions of inclusion modification based on the effective equilibrium reaction zone (EERZ) approach.

Aug 21, 2024