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Iron Ore 2017 Paper Number: 04

Channel iron deposits of the Western Robe River

E Beattie1

1. Exploration Geologist, Glencore, Douglas Qld 4814

ABSTRACT

Channel Iron Deposits (CIDs) are a subset of ooidal ironstone deposits that are almost unique to the Pilbara, where they represent nearly 20% of all Australia’s iron ore exports. Their genesis, age and geochemical variation are reasonably well understood, and the ores vary across the region according to these characteristics. CIDs such as Yandi (Marillana paleochannel) and the Robe paleochannel deposits are well described in terms of texture, grade and the distribution of contaminants throughout the ore. Comparatively less has been reported about the ores of the western Robe paleochannel between Pannawonica and Karratha. This presentation, based on a thesis undertaken throughout 2015 presents a characterisation of these CIDs using bulk rock geochemistry, XRD, thin section analysis and element mapping with the electron microprobe.

The majority of deposits in the western Robe are preserved as the inverted topography of the paleochannel, and most contained distinct wood-rich horizons. In comparison to the Marillana and eastern Robe ores, these deposits have similar grade, significantly less clay, and slightly higher aluminium. Similar to the eastern Robe ores, the pelletoids are generally spherical with a nuclei of haematitic fossilised wood, and the cortex to nucleus ratio is 2:1. Microprobe analysis revealed that the majority of aluminium is contained within goethite in ooid cortices, while silica and phosphorus present as dust-sized particles adsorbed to the pelletoid surfaces. Accordingly, the highest grade and lowest contamination is seen in samples with larger nuclui (hematite) and comparatively fewer cortices (goethite).

The geochemical characteristics suggest that the mafic Maddina Volcanics (directly upstream) contributed to these CIDs, in addition to the banded iron formations. Additionally, the volume of ferruginised wood, and the fact goethite will incorporate higher levels of aluminium in lower pH conditions (<5) points to formation in a soil rich in humic acids, and perhaps an environment with more vegetation than most of the areas upstream.

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The dynamic adhesion of wet and sticky iron ores onto impact plates

M Carr1, W Chen2, C Wheeler3 and K Williams4

1. PhD Candidate, TUNRA Bulk Solids – Research, Newcastle Institute for Energy and Resources, The

University of Newcastle, Callaghan NSW 2308 2. Research Engineer, TUNRA Bulk Solids – Research, Newcastle Institute for Energy and Resources, The

University of Newcastle, Callaghan NSW 2308 3. Associate Director, TUNRA Bulk Solids – Research, Newcastle Institute for Energy and Resources, The

University of Newcastle, Callaghan NSW 2308 4. General Manager - Research, TUNRA Bulk Solids – Research, Newcastle Institute for Energy and

Resources, The University of Newcastle, Callaghan NSW 2308

ABSTRACT

The depletion of favourable iron ore deposits in relation to their handleability is becoming a much more significant problem in comparison to previous years. With the depletion of these ores, the exploitation of less favourable ores must be considered. In addition, deeper excavation is required to meet the ever increasing demand of iron ore in the modern world. Lower deposits exhibit increasing clay and moisture content, leading to wet and sticky material (WSM) and problematic behaviours regarding handleability. WSMs are prone to cause problems in all phases of the materials handling streams, which is attributed to the inter-particle and boundary cohesion and adhesion forces.

This paper analysed the adhesion of bulk materials onto impact plates under dynamic conditions. A recirculating experimental setup was utilised to gain an understanding of the mode of failure that will be experienced for differing wall liner materials, wall liner angles and moisture contents. The main components of the research are the critical release angle of a problematic iron ore and the mechanism of plastic deformation as it impacts on a wall liner. The obtained results will enable for the optimisation of transfer systems in the materials handling stream for problematic ores.

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Determination of the handleability index of adhesive bulk materials

J Plinke1, M Carr2, W Chen3 and K Williams4

1. PhD Candidate, TUNRA Bulk Solids – Research, Newcastle Institute for Energy and Resources, The

University of Newcastle, Callaghan NSW 2308. 2. PhD Candidate, TUNRA Bulk Solids – Research, Newcastle Institute for Energy and Resources, The

University of Newcastle, Callaghan NSW 2308 3. Research Engineer, TUNRA Bulk Solids – Research, Newcastle Institute for Energy and Resources, The

University of Newcastle, Callaghan NSW 2308 4. General Manager - Research, TUNRA Bulk Solids – Research, Newcastle Institute for Energy and

Resources, The University of Newcastle, Callaghan NSW 2308

ABSTRACT

Economic drivers dictate the exploitation of formerly less attractive ore bodies located close to or even beneath the water table. These ores can cause handling problems and expensive downtime of processing equipment due to their increased adhesive characteristics and are colloquially termed as “wet and sticky” material.

In order to gain a better understanding of the causes of poor handleability, experimental test methods to determine wall adhesion and inter-particle adhesion within bulk materials were developed. Based on the combination of wall adhesion and inter-particle adhesion measurements, with traditional methods of assessing bulk material flowablility, a new method to assess the potential of bulk materials to cause handling problems is proposed. This method reduces the multitude of factors leading to problematic behaviour to an handleability index HI ∈ [0,1], which is easily assessed and understood. The method is suitable for adhesive materials and applicable for a wide range of material flow, from gravity reclaim stockpiles to transfer chutes and carry back on conveyor belts.

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Determination of iron ore mineralogy using fourier transform infrared spectroscopy – a chemometric approach

J Carter1, K Auyong1 and L Dixon1

1. Bureau Veritas Minerals Pty Ltd, Canning Vale WA 6155

ABSTRACT

Fourier Transform Infrared (FTIR) spectroscopy and other NIR tools have been used in the bauxite industry for many years. Infrared spectroscopy exploits the differences in chemical composition and lattice structure to produce a characteristic response. Spectral devices such as those from ASD Inc. and the HyloggerTM provide qualitatively mineralogical data targeted towards hydrated minerals detected in the near and short wave infrared region. The FTIR spectrum extends into the mid and thermal infrared range and can therefore respond to the presence of silicates and oxides in addition to hydrates and carbonates.

The key to successful utilisation of infrared spectra, however, is the interpretation methodology. In this study, FTIR spectra were calibrated against quantitative x-ray diffraction data for the determination of the mineralogy of iron ore. A full pattern profiling chemometric technique was utilised for the calibration, and the assessment of the regressions determined from an independent validation set. The abundance of key minerals, hematite, goethite, kaolinite and quartz were determined along with other minor minerals and chemical parameters and the results correlated against X-ray fluorescence assays and loss on ignition data. The results of the study indicate that spectral techniques using a full pattern profiling chemometric approach can be used successfully to obtain objective and quantitative mineralogical data to support field observations and analytical results for iron ore resource modelling. A comparison of this technique to the cost, quality and timeliness of other quantitative mineralogy tools is made.

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The geometallurgy of titanomagnetites that affects vanadium extraction

D Yan1, D Connelly1, J Floyd2 and G Das3

1. Minerals Engineering Technical Services, Midas Engineering Group 2. Graduate, WA School of Mines, Curtin University, Perth WA 3. CSIRO, Australian Minerals Research Centre, Waterford, WA

ABSTRACT

Tests have shown that there is a clear relationship between the amount of titanium in a titanomagnetite concentrate and the recovery of vanadium in an oxidizing salt roast-water leach. The vanadium recovery decreases as the amount of titanium in the ore increases. Similarly, in a reduction roast, as reduction conditions become more intense, the acid extraction of vanadium from the calcine decreases.

Scanning electron microscope analysis of tests samples showed that unleached vanadium, from salt roast-water leach residues, was associated with silicate gangue and high titanium oxides.

Reductive roasting to produce metallic iron redistributes the vanadium into the titanium oxide lattice making the vanadium more refractory to salt roasting and acid leaching.


Optical image analysis of iron ore pellets using CSIRO software mineral4/recognition4

E Donskoi1, A Poliakov1, S Hapugoda1 and L Lu1

1. CSIRO Mineral Resources, Qld 4069, Australia

ABSTRACT A significant amount of metallic iron in the world is produced in blast furnaces from iron ore pellets. To control the quality of pellets and to optimise pellet production, characterisation of both green and fired pellets is required. Optical image analysis (OIA) allows identification of different minerals, binder, remaining fluxes and porosity within pellets.

For proper identification of the mineralogy, porosity and texture in pellets, a high magnification is required so that each individual image covers only a very small portion of the pellet. However, the characterisation of pellets requires imaging of the whole pellet as a single object, so the size of the resulting overall image can make it difficult to handle. A solution to this problem has been implemented within the CSIRO OIA package by combining images at different levels. To average out local irregularities, individual images can be combined during imaging in Mineral4 into larger MosaiX images. Mineral4 further combines the MosaiX images into one panorama image of the whole pellet.

The proposed procedures allow calculation of mineral and porosity spatial distributions, local gradients and abundance graphs based on the distance from the centre of the pellet. The “Pellets” module of CSIRO OIA software also allows characterisation of large pieces of iron ore lumps and sinter.

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Digital rocks for iron ore sinters – toward a 3D quantification of sinter textures

B Godel, B Ellis, D O’Dea, T Honeyands and T Harvey

1. Senior Research Scientist, CSIRO, Kensington, Australia

ABSTRACT

X-ray computed tomography (XCT) is a non-destructive technique that allows the exploration of the internal structure of solid objects in three dimension (3D). Over the past ten years, the combination of XCT with more conventional 2D techniques and quantitative 3D image processing and analysis (commonly referred to as digital rocks) allowed to address some of the most challenging problems in ore deposit studies. The range of X-ray energies used in XCT allows the X-rays to be transmitted through complex and dense materials including iron ores (e.g. sinters, lumps, granules). Recent high-resolution X-ray computed tomography scanners have the ability to generate multi-scale (25 down to 0.3 µm voxel size) imaging of a given sample enabling the characterization of 3D textures across a range of scales. This paper will focus of the application of digital rocks to iron ore sinter particles (using filtered polychromatic X-ray beam). The paper will be divided into three parts and will include: i) details on the methodologies including their benefits and limitations and the effect of spatial resolution; (ii) the quantification of pore network topology and pore characteristics (e.g. open versus closed pores, pore size distribution and pore morphologies; degree of connectivity of the pore network and its tortuosity); and (iii) the evaluation of the technique to characterize various phases within the material and quantify 3D mineral textures.

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Analysis of 98 individual -200 mesh iron-ore samples in a single MLA session

D C Grant1 and D J Goudie1

1. Memorial University of NL, Canada

ABSTRACT

Our lab has recently published our efforts towards increasing the throughput of automated mineralogy (MLA) systems by producing single-step trans-vertical moulds, rather than traditional 30 mm polished epoxy moulds. Due to the small particle size of iron ore grains in the -200 mesh size fraction (<75 µm), not all of the surface area on the mould is needed for measurement to achievement a good statistical representation. In a new study, trimming of the excess area of the mould results in a smaller sample, and increases the quantity of unique samples that can fit in a newly designed trans-vertical adapter for a MLA 650 FEG SEM. The complete analysis required 80 hours and each sample had an average of 41 000 particles measured and identified. The analysis was calibrated to allow for offline discrimination of hematite/magnetite. Comparisons between the calculated Fe-assay derived from MLA results are compared to those from bulk sample, and show how the Fe assay has a correlation coefficient of >0.99 when the particle count reaches this number, but measuring extra particles yields very little benefit. This study represents the most expedient method yet reported to prepare well-polished samples and identify them in a timely manner that can allow for quicker results in process mineralogy.

REFERENCES Grant, D.C., Goudie D.J., Shaffer, M and Sylvester, P. 2016. A single-step trans-vertical epoxy preparation method for

maximising throughput of iron-ore samples via SEM-MLA analysis. Applied Earth Science: TIMM B, 125, (1), 57-62.

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Discriminating hematite/magnetite via scanning electron microscope-mineral liberation analyser (SEM-MLA) in the -200 mesh size fraction of iron ores

D Grant1, D Goudie, C Voisey, M Shaffer and P Sylvester

1. SEM-MLA Research Coordinator, Memorial University of NL, Newfound, Canada

ABSTRACT

Scanning electron microscopy – Mineral Liberation Analysis (SEM-MLA) can be used to discriminate between hematite/magnetite in iron-ores, but achieving BSE segmentation between the two minerals is difficult for particles ≤ 75 µm using typical preparation and analysis methods for the MLA based on a Quanta 400 (25 kV high voltage) SEM. Decreasing the HV setting to 15 kV, using a slow-speed polishing method, and conducting the experiment on a MLA Quanta 650 FEG SEM, reduces instrument noise and results in very clean BSE images and segmentation. This method requires new x-ray standards to be acquired for each mineral identity at 15 kV because of major changes in the spectra at lower kV. However, once these x-rays are added to the mineral reference list, very clean segmentation can be achieved and a proper analysis obtained.

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Infrared spectroscopy in BHP Billiton iron ore with a focus on in-mine infrared sensing

M Haest1, D Mittrup1 and L Edwards1

1. BHP Billiton Iron Ore, Perth WA 6000

ABSTRACT

BHP Billiton Iron Ore has embedded full range visible to longwave infrared scanning of pulverised exploration samples since 2014. An automated algorithm that combines infrared spectra and assays is delivering mineralogy for every sample that is being drilled, as well as predictions of stratigraphy. Work is ongoing to include predictions of geometallurgical and geotechnical properties for these samples.

Further along the mining value chain, infrared scanners have been installed over conveyor belts to track the properties of materials that cause issues in the processing plant. A series of infrared sensing trials in the mine (blast hole samples and mine faces) is being completed to understand if in-mine infrared sensing can fill the knowledge gap in the value chain. These trials will show whether such data can exploit learnings from either exploration or processing to predict downstream properties of ores that are being mined.

This study will summarise how infrared sensing is currently delivering value to BHP Billiton Iron Ore and it will describe in detail the results from the in-mine infrared sensing trials. The latter will include discussions on:

• Integration of disparate datasets (visible-near to shortwave infrared, thermal infrared and LIDAR image cubes, data from blastholes including elemental composition and infrared spectra)

• Potential for in-mine delineation of problematic materials (eg ultrafine ores)

• High resolution definition of ore-waste boundaries

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Highlighting key features of the pore structure of iron ore sinter

T Harvey1, D O’Dea, G Evans, B Godel and T Honeyands

1. PhD Candidate, The University Of Newcastle, Newcastle, Australia

ABSTRACT

The pores within iron ore sinter are important for producing a high quality material that is strong and easily reduced. The meso-pores with high surface area are important for reducibility, whilst the thickness of the walls between pores influences strength. The complementary methods of mercury intrusion porosimetry (MIP) and X-ray CT were used to characterise the structure of industrial and pilot scales sinters across a wide range of pore sizes (3 nm to 100 μm for MIP and 50 μm to 5 mm for CT). Ideally, the MIP and CT can be combined to provide a more complete description of the overall pore structure from which quantitative measures can be obtained. To do so, however, is challenging given the inhomogeneous nature of sinter and the statistical variation in the measurements themselves. In this study, the generalised additive modelling (GAM) approach, using the open source statistical software package, R, has been applied to highlight where there are peaks in the concentration of pore sizes. Importantly, the shape of the GAM-fitted function and the heights of the peaks show statistically significant differences between samples. For the samples investigated, the GAM-fitted functions for the MIP volume distribution of pore diameters were found to have a common set of distinctive peaks at 0.003, 0.4 and 10 μm. The GAM approach was also applied to the X-ray CT measured pore wall thickness, highlighting a single peak whose position varies between samples. The cause of these distinctive peaks and their implications for sinter quality are discussed.

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Evaluation of sintering behavior based on ore characteristics

T Higuchi1 and L Lu2

1. Steel Research Laboratory, JFE Steel Corporation, JFE Steel Corporation Fukuyama, Japan 2. CSIRO Mineral Resources, Kenmore, QLD 4069, Australia

ABSTRACT

The quality of iron ore fines have been deteriorating, which has affected sinter quality and productivity adversely. New pretreatment and sintering technologies are therefore required to tackle with the gradual change in the quality of iron ore fines. In the sintering process, iron ore fines are first granulated with fluxes such as limestone and coke breeze, and are then loaded and fired in a sinter machine. Sinter productivity and quality are heavily influenced by the reactions occurring in the sintering bed. Hence fundamental understanding of these high temperature reactions is urgently needed.

Formation of initial sinter melt, penetration and assimilation of nucleus particles by the initial melt, and consolidation and final solidification of sinter melt are believed to be the key sintering reactions. The assimilation degree and penetration depth have been studied separately in the literature with model particles and diffusion couples and are therefore difficult to be related to sinter quality In addition, the effect of ore mineralogy has not been studied in details.

In this study, tablets consisting of coarse particles from various iron ore fines as nucleus particles and chemical reagents as matrix materials were made and fired under various sintering conditions to investigate the penetration and assimilation behavior simultaneously. The degree of assimilation, pore structure, compressive strength of the resultant analog sinters were evaluated and the relationship between sinter strength and ore characteristics was further discussed. The nucleus particles from Australian ores were found to be more porous and assimilated more readily with sinter melt, resulting in a viscose melt and a macro-porous sinter structure. The nucleus particles from Brazilian ores, on the other hand, assimilated less readily with sinter melt, resulting in a fluid melt and a denser sinter structure. This is consistent with the results reported in the literature, suggesting that this evaluation method can be utilized for studying sintering reactions and predicting sinter quality.

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VisuMet - Analyses of iron carriers with image processing

B Kain-Bueckner1 and H Mali2

1. Researcher, K1-Met GmBh, Austria.

ABSTRACT

VisuMet processes micro-images of iron carriers like iron ores, pellets and sinter. The samples are embedded in resin and polished. The image acquisition takes place automatically at pre-defined positions with an optical microscope (Zeiss Axio Observer Z1m). The magnification depends on crystal sizes and texture of the sample.

The software has been improved until know based on microscopical investigations of more than 3000 different polished sections. The collection comprises more than 80 iron ores and 50 pellet brands, which had been produced worldwide. In addition reduced samples from standard reduction tests of iron ore, pellets and sinter complete the collection.

The evaluation of the iron ores is based on the heterogeneous reduction speed of the main minerals limonite, hematite and magnetite. A concentric phase front movement model was integrated in the simulation of the reduction front. A discrete amount of shells, depending on the kind of mineral, will be removed by every step of the calculation. As a result VisuMet displays the removed area as degradation curve, which can be assigned with quality fields.

The quality assessment of the pellets is premised on the pore size. The pores are assumed to be circularly and the diameter is calculated from the pore area. The greater the amount of “big” pores the faster the pellet brand can be reduced.

The phase portions are normally determined by point counting. As a general rule 500-1000 points are being counted per section depending on homogeneity of the mineral distribution. For the comparison of the point counting method with VisuMet, two sections of each iron carrier were enumerated and images were acquired at the same positions. Overall 14.400 points were evaluated. The results were compared to the data of 720 images analyzed by VisuMet. The correlation coefficient is 99,67 %.

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The use of FEG-SEM in association with other identification techniques in solving complex iron ore mineralogy

M Lacoste1 and A Correa de Araujo

1. Research Engineer, ArcelorMittal, France

ABSTRACT

Field-emission gun scanning electron microscope (FEG-SEM) is a powerful tool for the identification and quantification in ore applied mineralogy. In the FEG-SEM, the function of the gun is to produce an extremely narrow beam of electron of precisely controlled energy. The tungsten filament used in a FEG has the ability to create a beam as small as 10nm. As a result, a FEG-SEM provides higher spatial resolution, accurate measurement of light elements and several alternatives for elemental mapping. The present work presents one specific case in which FEG-SEM was used in combination with optical microscopy, conventional SEM and X-ray diffraction to define in one hand the complex phosphate mineralogical composition of a European iron ore. The FEG analyses were able to determine all phosphate-bearing phases (12 differents in total), some quite unique to the ore sample tested. Even slight compositional variations of Goedkenite [(Sr,Ca)2Al(PO4)2(OH)] with high and low Sr content were clearly differentiated.

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Variation of elastic modulus and friction coefficients of iron ore granulated mix with moisture content

C Li1, R Moreno-Atanasio2 and T Honeyands 1

1. Centre for Ironmaking Materials Research, School of Engineering, The University of Newcastle, Callaghan,

NSW 2308, Australia 2. Centre for Advanced Particle Processing and Transport, School of Engineering, The University of Newcastle,

Callaghan, NSW 2308, Australia

ABSTRACT

The behaviour of iron ore granules in the feeding process of sintering is significantly influenced by the material properties of the granulated mix. Measurement of key material properties of the iron ore granulated mix is indispensable prior to the simulation of the sintering process based on the discrete element method (DEM). In this paper, three key property parameters of the studied iron ore granulated mix, including elastic modulus, static and rolling friction coefficients, were considered and measured in laboratory-scale experiments. For different sintering processes, the moisture content of the granulated mix normally varies according to the specific requirements for granule size distribution and operating conditions. Therefore, understanding the effect of moisture content on the property parameters of iron ore granules is very helpful to accurately determining the property parameters for DEM simulation research. In this work, five groups of iron ore granule samples with five levels of moisture contents were prepared through granulation and the trends in elastic modulus, static and rolling friction coefficients with the increase of moisture content were plotted and analysed based on the corresponding experimental measurement results.

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Goethite classification, distribution and properties with reference to Australian iron deposits

J R Manuel1 and J M F Clout2

1. Project Leader, CSIRO Mineral Resources, Kenmore, QLD 4069 Australia 2. Principal, John Clout and Associates, Nedlands, WA 6909

ABSTRACT

The importance of goethite to Australian iron ore production is steadily increasing as the proportion of goethite-rich, martite-goethite bedded and channel iron deposits increases at the expense of declining production from high grade microplaty hematite deposits. For this reason, an improved understanding of goethite-bearing iron deposits, goethite types and their physical and metallurgical properties is vital to maintaining optimum sintering and blast furnace performance in Asian steel mills.

The terminology used to describe goethite in Australian iron deposits is currently highly variable, the continued use of the discredited mineral name ‘limonite’ for goethite is still in widespread use and there are many misconceptions concerning goethite chemical grade and downstream physical and metallurgical properties. The classification proposed here is based on the geometallurgical characteristics of goethite types, which range in character across a spectrum from hard brown to black vitreous goethite with low porosity, to highly microporous, friable, yellow ochreous goethite. In between is a continuous range of increasingly porous and earthy, brown goethite types, with highly variable morphology and of primary or secondary origin.

In practice, typical vitreous goethite with highly reflective surfaces and conchoidal fracturing, characteristic of deposit hardcap may be indistinguishable in terms of chemical composition, including loss on ignition, and microstructure, from the dull brown, hard goethite found in primary deposits. There is also a common misconception that friable earthy or yellow ochreous goethite is high in chemical impurities (primarily Al and Si) and an undesirable sinter fines component, whereas in fact it may be very beneficial in promoting granulation and primary melt formation during sintering.

This paper defines a goethite classification in terms of geometallurgical characteristics that is intended to clarify some of the existing confusion surrounding goethite properties in iron deposits, with particular emphasis on Pilbara iron deposits and considers the advantages and potential limitations of goethitic components in Asian sinter blends.

Keywords: goethite, goethite geometallurgy, goethite sinter properties

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A new iron ore sintering nucleus assimilation test

J R Manuel1 and N A Ware2

1. Senior Experimental Scientist, Geometallurgy Team, CSIRO Mineral Resources, Kenmore QLD 4069 2. Experimental Scientist, Geometallurgy Team, CSIRO Mineral Resources, Kenmore QLD 4069

ABSTRACT

The reactivity and assimilation properties of iron ore types of different mineralogy and texture are critical to sintering performance and optimised performance depends on balanced blend fine ore nucleus and matrix characteristics. Coarser ore nuclei react with the melt formed from fine (-1 mm) ore and flux particles and physically reinforce the resulting sinter structure. The extent to which ore nuclei react and assimilate with the sinter melt affects the overall melt volume formed during sintering and influences the chemistry and physical properties of the melt (e.g. flow properties), as well as the strength/productivity balance of the sinter and its reducibility.

A new technique for the assessment of nucleus assimilation properties has been trialled in the laboratory, using natural ores and fluxes. A standard -1mm matrix blend was prepared and mixed with nucleus particles screened from the -4+2 and -2+1 mm size fractions of representative individual ore types, to compare their reactivity under typical sintering conditions.

Additional samples were tested to determine the effects of heating and dehydroxylation on nucleus particle volume and cracking. Measurements of fired samples were carried out via microscopic optical image analysis of polished sections. Ore types tested included dense hematite-goethite, intermediate hematite-goethite and microporous, ochreous goethite.

Results have been compared with those from qualitative tests carried out under the same conditions using nucleus cores of different sizes, obtained from lump ore samples. An attempt has been made to develop a quantitative index of relative assimilation performance for selected individual ore types and evaluate the effect of nucleus size (essentially surface area: volume ratio) on the kinetics of the assimilation process.

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Geometallurgy – a new perspective on high-grade iron ore deposit at Kiirunavaara, Northern Sweden

K Niiranen1

1. Process Mineralogy, LKAB, SE-981 86 Kiruna, Sweden

ABSTRACT

LKAB (Luossavaara-Kiirunavaara AB) is operating an iron ore mine, three concentration plants and three pelletizing plants in Kiruna. The methods of separation at the beneficiation plants today are low intensity magnetic separation (LIMS) and reverse apatite flotation, where the wet LIMS is regarded as the crucial part of silica separation from the ore. Due to the fact that the silica level is expected to increase in the incoming material to the beneficiation plants in Kiruna in the future, geometallurgy has become an important area of development and research at LKAB. A laboratory scale methodology was developed for the systematic characterisation of the ore for mineral processing with the focus on the high silica ore type B2 with newly discovered subtypes. This methodology is combining mineralogical, geochemical and process mineralogical characteristics. Automated mineralogy (QemScan) was used to study the modal mineralogy, the distribution of silicate minerals in different particle size classes after comminution, the deportment of silicon (Si) between various silicates and degree of liberation and intergrowth of magnetite and silicates. An essential stage of systematic characterisation of the ore deposit for mineral processing is the estimation and simulation of different parameters from the laboratory scale to the full scale at the concentration plants using empirical models based on the data collected at the mineral processing plants. As the first step to implement geometallurgical information, the current geological model is reconstructed with the mineralogy and the two subtypes of high silica ore type B2 are separated into different domains. To study the reducing the SiO2 content in the magnetite concentrate, a reverse cationic silicate flotation laboratory test program in large scale was initiated in early spring 2016 related to potential silicate flotation at the beneficiation plants in the Kiirunavaara site. Furthermore, the second target is to implant mineral processing parameters into the existing block model. This information provides a good basis for making prognosis for the mine planning and the quality prognosis on the crude ore for mineral processing.

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Microwave-assisted magnetising roasting and mineral

transformation studies of low-grade, goethite-rich iron

ores

V Nunna1, S Hapugoda and M Pownceby

1. CSIRO Mineral Resources, PO Box 883, Kenmore, QLD 4069

ABSTRACT

Deposits of low grade iron ores containing abundant goethite are distributed across the world. A common difficulty associated with beneficiating goethitic-rich ores is the poor liberation characteristics of the iron-bearing minerals which often contain finely disseminated gangue minerals such as kaolinite, gibbsite and quartz. Microwave-assisted heating has been proposed as an effective way of inducing dehydroxylation and associated mineral transformations in order to beneficiate low grade goethitic ores. In this research, the mineral transformations occurring in a low grade goethite-rich sample using microwave radiation was studied. Roasting conditions (up to 1000°C and under various CO/CO2 gas atmospheres) were designed to generate a magnetic product from a goethite-rich, reject waste stream sample sourced from an iron ore processing site in the Pilbara, Western Australia. Conditions for transforming the raw material from hydrated goethite to hematite and eventually to maghemite are presented. Chemical and mineralogical characterization of the raw material and roast products were conducted using XRF, XRD, optical microscopy and SEM techniques to identify the mineralogical and chemical changes occurring during the heat treatment. Further steps are suggested to optimize the microwave-assisted magnetizing roasting and correlate it with the application of magnetic separation techniques to maximize the efficiency of upgrading the iron content in low grade iron ores.

Keywords: Goethite, hematite, microwave-assisted roasting, magnetic separation.

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Microhardness testing of hematite-goethite Fe ores – implications for their textural characterisation and geometallurgy

M Peterson1, J Manuel1 and S Hapugoda1

1. Senior Experimental Scientist, Iron Ore Geometallurgy Team, CSIRO Mineral Resources, Kenmore Qld 4069

ABSTRACT

Microindentation testing using the square-pyramid-shaped Vickers indenter is a well-established technique to determine the microhardness of minerals and materials. However there is a paucity of published microhardness data from Fe ore samples. It is acknowledged that an iron ore’s particle mineralogy and texture is critical to its processing properties, and it is therefore considered that the microhardness of different mineralogical/textural types may also relate to these properties. Mineral microhardness potentially provides inputs to the modelling of breakage characteristics during comminution, as well as the relationship between mineral chemistry and microhardness, and mineral microporosity and microhardness. Microhardness can be determined as single crystal microhardness, for relatively more coarsely microcrystalline samples, or as ‘aggregate microhardness’ for cryptocrystalline or finely microcrystalline samples.

Variations in the texture and mineral chemistry of common Fe ore minerals (e.g. martite and microplaty hematite, ochreous and vitreous goethite, etc.) are well established and this study provides microhardness data on different textural forms of Fe (oxyhydr)oxides from a variety of different Fe ore deposits. The data indicated that in general, the mineral grain size, microporosity and texture were the main influences on Fe (oxyhydr)oxide microhardness. There were no apparent systematic variations between microhardness and minor element mineral chemistry, with the possible exception of Al content in goethite (for goethites with Al content > 0.5 wt %), and for goethite total element contents >90 wt% (determined by electron probe microanalysis, EPMA). Higher Al concentrations and lower total element concentrations in goethite EPMA analyses correlated with lower goethite microhardness. Microporosity and grain size were more important than texture to hematite microhardness. Different textural forms of dense hematite (e.g. martite, recrystallised interlocking hematite and specular hematite) with similar grain size exhibited comparable microhardness. Microhardness values for hematite and hydrohematite with little or no evident microporosity were also similar, whereas more porous forms of martite, microplaty hematite or hydrohematite exhibited lower microhardness.

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A comparison of X-ray based analysis techniques for characterising the phase mineralogy and associated alumina deportment in iron ores

M I Pownceby1, C M MacRae2 and A Torpy3

1. Team Leader Iron Ore Geometallurgy, CSIRO Mineral Resources, Clayton South VIC, 3169 2. Team Leader Microbeam Laboratory, CSIRO Mineral Resources, Clayton South VIC, 3169 3. Senior Research Technician Microbeam Laboratory, CSIRO Mineral Resources, Clayton South VIC, 3169

ABSTRACT

In this study, electron probe micro-analysis (EPMA) was used to identify and quantify the deportment of alumina within mineral phases in iron ore samples (-1mm crushed) sourced from different suppliers. Results were directly compared with quantitative mineralogical data derived from x-ray diffraction (QXRD) to provide an evaluation of the relative merits of both techniques. The four ores studied contained alumina either in the form of gibbsite (Al(OH)3), aluminosilicates (e.g. kaolinite (Al2Si2O5(OH)4)), or alumina associated with goethite.

For the minor phases gibbsite and kaolinite, the abundance trends measured via QXRD were generally reflected in the EPMA data. Agreement was less satisfactory for the more abundant goethite phase (both low- and high-Al forms). The discrepancy may be the result of sampling issues arising from textural features such as grainsize, and also a systematic overestimate in the amount of Al-rich goethite when hematite and Al-bearing phases are finely intermixed and the EPMA step size is coarse. A second difference in the EPMA results compared to the QXRD data was in regard to quantification of low-Al and high-Al goethite phases. The sensitivity of the chemical-based EPMA was better for distinguishing between high- and low-Al goethite although the results remain overprinted by potential errors introduced via sampling.

EPMA and QXRD techniques are capable of providing high-quality quantitative information regarding the phase mineralogy and deportment of alumina within iron ore samples. The techniques use different methodologies in determining the mineralogical information (i.e. structural versus chemical) which introduces some limitations. Care should therefore be taken when directly comparing results from each method although in general the data should be considered complimentary as each approach provides slightly different results and interpretations regarding the overall mineralogy.

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Summary of results of an international round robin on mineralogical analysis of iron ores

M D Raven1 and S L Birch2

1. CSIRO Land and Water, Adelaide, South Australia 2. CSIRO Mineral Resources, Adelaide, South Australia

ABSTRACT

Global demand for iron ore is leading to diversification of iron ore sources. As supplies of high grade iron ore are being rapidly consumed, it has become necessary to acquire accurate quantitative mineralogical analysis of lower grades in order to maintain production and maximize the life of ore reserves.

While high-precision, quantitative X-ray Fluorescence (XRF) spectrometry methods have been the principal techniques to characterize the elemental composition of iron ores, standard methods to quantitatively determine the mineralogy have been lacking. An obvious method for determining the mineralogy of ores is X-ray diffraction (XRD) but, unlike XRF, there are no ISO, AS or ASTM standard methods for XRD analysis of iron ore materials. Consequently, current XRD methods vary markedly from laboratory to laboratory. XRD techniques can be very dependent on sample preparation techniques, the choice of instruments and settings, and often the knowledge and experience of the analyst. Development of a standard method would define best practice for quantitative XRD analysis of iron ores.

An initial step towards preparing a standard method for XRD analysis of iron ores was to determine the current state of precision and accuracy of XRD and to gauge how successfully XRD can characterize the mineralogy of iron ore materials. In this regard, CSIRO organized an international round robin to analyze six iron ore reference materials previously prepared and certified for chemistry by CSIRO. Anyone was invited to enter the round robin provided that XRD was the principal method of quantitative mineralogical analysis. However, participants were encouraged to use any number of ancillary techniques to assist with their final submission.

A summary of more than 120 results of the round robin from more than 80 participants will be presented, along with preliminary recommendations for a standard method of analysis of iron ores by XRD.

Keywords: iron ore, round robin, standard method, XRD

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The softening and melting behaviour of single and mixed iron ore burden

L Wang1

1. PhD, University Of Science and Technology Beijing, Beijng, China

ABSTRACT

The cohesive zone in the blast furnace is largely affected by the softening and melting behavior of ferrous burden because of its vital role in the blast furnace process. A new research method- Visual High Temperature Methodology (VHTM) -has been given to study the softening and melting behavior of sinter, 2 kinds of lump ores and acid pellet intuitively. Before softening, both 2kinds of lump ore swelled and more serious for lump ore B because of its denser structure than lump ore A. The softening and melting temperature intervals are different from one another and this phenomenon contributed to the gas permeability of ore layer in the cohesive zone since the “ore window” has formed. Besides, the softening and melting behavior of mixed burdens have been study and found that the softening and melting characteristics of mixed burden A (consists of sinter and lump ore A) is better than mixed burden B (consists of sinter and lump ore B) and mixed burden C (consists of sinter and acid pellet) despite poorest characteristics of lump ore A. The reason is that the high temperature interactivity between lump ore A and sinter is much better than lump ore B and acid pellet. The high temperature interactivity is mainly influenced by the chemical compositions, porosity and contact area. This paper provides a new research method for softening and melting behavior of iron ore and important technical basis for the optimisation of blast furnace burden.

Iron Ore · PDF fileA significant amount of metallic iron in the world is produced in blast furnaces from iron ore pellets. To ... Iron Ore 2017 . on: )

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