This project examined the reduction and formation of cementite from hematite and titanomagnetite ores and cementite stability. The aim of the project was to develop further understanding of cementite stability under conditions relevant to direct ironmaking and the mechanism of cementite decomposition. The reduction of hematite and ironsand by hydrogen-methane-argon gas mixtures was investigated from 600??C to 1100??C. Iron oxides were reduced by hydrogen to metallic iron, which was carburised by methane to form cementite. The hematite ore was reduced more quickly than the ironsand. Preoxidation of the ironsand accelerated its reduction. Hematite was converted to cementite faster than preoxidised ironsand. The decomposition of cementite formed from hematite was investigated from 500??C to 900??C. This cementite was most stable at temperatures 750-770??C. The decomposition rate increased with decreasing temperature between 750??C and 600??C and with increasing temperature above 770??C. The stability of cementite formed from pre-oxidised titanomagnetite was studied from 300??C to 1100??C. This cementite was most stable in the temperature range 700-900??C. The rate of decomposition of cementite increased with decreasing temperature between 700??C and 400??C and with increasing temperature above 900??C. Cementite formed from ironsand was more stable than cementite formed from hematite

This project examined the reduction and formation of cementite from hematite and titanomagnetite ores and cementite stability. The aim of the project was to develop further understanding of cementite stability under conditions relevant to direct ironmaking and the mechanism of cementite decomposition. The reduction of hematite and ironsand by hydrogen-methane-argon gas mixtures was investigated from 600??C to 1100??C. Iron oxides were reduced by hydrogen to metallic iron, which was carburised by methane to form cementite. The hematite ore was reduced more quickly than the ironsand. Preoxidation of the ironsand accelerated its reduction. Hematite was converted to cementite faster than preoxidised ironsand. The decomposition of cementite formed from hematite was investigated from 500??C to 900??C. This cementite was most stable at temperatures 750-770??C. The decomposition rate increased with decreasing temperature between 750??C and 600??C and with increasing temperature above 770??C. The stability of cementite formed from pre-oxidised titanomagnetite was studied from 300??C to 1100??C. This cementite was most stable in the temperature range 700-900??C. The rate of decomposition of cementite increased with decreasing temperature between 700??C and 400??C and with increasing temperature above 900??C. Cementite formed from ironsand was more stable than cementite formed from hematite

Thesis (Ph.D.)--University of Wollongong, 2005. / Typescript. Includes bibliographical references: p. 198-203.

Un procédé innovant de production de fer par électrolyse d’une suspension d’oxydes de fer en milieu alcalin concentré est développé au centre de recherche d’ArcelorMittal de Maizières-lès-Metz. Ce procédé s’il atteignait la maturité industrielle permettrait de réduire significativement les émissions de dioxyde de carbone associées à l’industrie sidérurgique, en remplaçant le carbone utilisé comme agent réducteur dans les hauts-fourneaux par de l’électricité. Bien que ce procédé permette la production de fer à partir d’hématite commerciale (Fe2O3) à une densité de courant de l’ordre de 1000 A.m-2 avec une efficacité faradique supérieure à 80%, une dégradation des performances est systématiquement constatée lors de l’électrolyse de minerais de fer. Les impuretés majoritaires de ces minerais sont les oxydes et hydroxydes d’aluminium et de silicium, des composés solubles dans la soude concentrée. Ces composés pourraient donc être à l’origine de la baisse de réactivité observée lors de l’alimentation du procédé par des minerais de fer. Ainsi afin de tenter d’améliorer les performances de l’électrolyse alcaline à partir de minerais, des traitements de lixiviation alcaline sur un minerai défini ont été effectués dans cette thèse. La réactivité des minerais avant et après traitement a été comparée par chronoampérométrie. Bien que suite à l’élimination de ses composés alumineux, le minerai traité ait vu son rendement faradique réhaussé à environ 80% pour une valeur avant pré-traitement de 65%, sa densité de courant est restée deux fois moins élevée que celle de l’hématite pour une même tension électrique appliquée. Des expériences d’ajout d’ions aluminates et d’ions silicates lors de l’électrolyse d’hématite pure n’ont de plus eu pratiquement aucun effet indésirable sur son électrolyse. Les diverses expériences conduites dans cette thèse laissent supposer que les impuretés traitées n’ont que peu d’influence sur la réactivité des minerais. Le procédé est en revanche très sensible à la granulométrie des particules de minerais. Par ailleurs de forts phénomènes d’agglomération, qui n’ont pas lieu avec les oxydes de fer purs, ont été constatés lors de mesure de granulométrie du minerai étudié. Ainsi les expériences réalisées laissent supposer qu’un autre phénomène, probablement lié à la granulométrie secondaire des minerais en milieu alcalin concentré, soit à l’origine de la baisse de réactivité observée lors de leur électrolyse. Parallèlement une analyse thermodynamique avancée a été menée afin de déterminer les meilleures conditions théoriques de pression, de température et de concentration en NaOH pour effectuer l’électrolyse de l’hématite. La solubilité des composés de la gangue a été représentée avec des équations de Pitzer, et de nouveaux paramètres ont été calculés pour les interactions Na-SiO3-Al(OH)4. Cette étude thermodynamique a permis la conception et le pré-dimensionnement d’une étape de traitement des minerais par lixiviation alcaline / An innovative ironmaking process by alkaline electrolysis of suspended iron oxides is being developed at ArcelorMittal Global R&D Maizières-lès-Metz. Were it to achieve industrial maturity, this process would permit a significant reduction of steelmaking CO2 emissions. Indeed, the use of carbon as a reducing agent in blast furnace would be replaced by electricity. Although this process enables iron production from commercial hematite (Fe2O3) at current density of 1000 A.m-2 with faradaic efficiency higher than 80%, these performances are systematically lower when using iron ore instead. The main impurities in these ores are aluminium and silicon oxides and hydroxides, these compounds are soluble in concentrated sodium hydroxide solutions. These compounds could be the source of the decrease in reactivity observed when feeding the process with iron ores. To raise the electrolysis performance with iron ores, alkaline leaching treatments were conducted on a defined iron ore. Reactivity of iron ores before and after treatment was compared by chronoamperometry. Although the elimination of aluminous compounds resulted in the ore gaining a faradaic yield increase to a value of 80%, compared with 65% before treatment, its current density remained twice as low as the one of hematite for a same applied voltage. Furthermore, complementary experiments of aluminate and silicate ions addition during pure hematite electrolysis did not have any deleterious effect on its electrolysis. Based on all the experiments undertaken in this PhD, it seems unlikely that siliceous and aluminous impurities hold an important effect on iron ore reactivity in alkaline electrolysis. The process is nonetheless very sensitive to iron ores granulometry. On this subject, strong agglomeration phenomena were witnessed when measuring iron ores granulometry but did not occur with pure iron oxides. Therefore, it would seem that other phenomena may be the main cause of reactivity loss, these phenomena may well be linked to secondary granulometry of iron ores in concentrated alkaline media. In parallel, an advanced thermodynamic analysis was carried out to describe the best theoretical conditions for pressure, temperature and NaOH concentration to realize hematite electrolysis. Gangue compounds solubility was represented with Pitzer equations, and new parameters were calculated for Na-SiO3-Al(OH)4 interactions. This thermodynamic study enabled the design and pre-sizing of a treatment step for iron ores by alkaline leaching

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Science, 1980. / Microfiche copy available in Archives and Science. / Bibliography: leaves 79-80. / by Andrew G. Hudson. / M.S.

[Truncated abstract] Detailed sedimentological, petrographical, geochemical and palynological studies have provided insight into the source rocks and the processes that operated during formation of the Tertiary Yandi channel iron deposit (CID) of the eastern Pilbara, Western Australia. Yandi is the largest and most valuable CID in the world, accounting for more than 2.5% of global iron production in 2003, and is the type-example of CID. The Yandi CID occupies the palaeo-Marillana Creek in the central Hamersley Ranges. It is near-coincident-with the modern Marillana Creek which incised Proterozoic bedrock of the Weeli Wolli Formation (Hamersley Group) and associated dolerite intrusions. Three lithostratigraphic units fill the palaeo-Marillana Creek and comprise the Marillana Formation. The units in stratigraphic order are the: (1) Munjina Member; (2) Barimunya Member, which hosts the majority of the iron resource; and (3) Iowa Eastern Member. Fossil pollen and spores in organic-rich claystones in the Munjina Member indicate that deposition of the Marillana Formation most likely commenced in the Early Oligocene in response to erratic seasonal flows with high energy flood events and intervening quiescent suspension settling of clays. The Marillana Formation consists of twelve facies. These conglomerate and clay facies form three facies associations. The basal facies association is composed of polymictic conglomerate, clay and interbedded CID that represents a lag deposit along the base of the palaeochannel. This facies association characterises the Munjina Member. The second facies association consists of iron-rich conglomerate sheets, bars and subordinate scour-fills and characterises the Barimunya Member. Channel iron deposits of the overlying Iowa Eastern member consist of reworked Barimunya Member iron conglomerates. The upper facies association is polymictic conglomerate with clay that characterises the remainder of the Iowa Eastern Member. Polymictic iron conglomerate in the Munjina and Barimunya Members contains Weeli Wolli Formation and dolerite clasts indicating local derivation. Rare earth element profiles of the other iron conglomerate facies indicate derivation of the Barimunya and Iowa Eastern CID from a different source. These iron conglomerates are characterised by relatively flat LREE profiles. The LREE exhibit an enriched profile approaching the MREE [(average La/Nd)N = 0.7], and the HREE profile shows minor enrichment approaching ytterbium [(average Dy/Yb)N = 0.9]. Comparison of iron conglomerate REE profiles to those of the bedrock indicates that these conglomerates were most probably derived from the Joffre Formation BIF of the Hamersley Group

[Truncated abstract] Banded iron formations of the ~27702405 Ma Hamersley Province of Western Australia were locally upgraded to high-grade hematite ore during the Early Palaeoproterozoic by a combination of hypogene and supergene processes after the initial rise of atmospheric oxygen. Ore genesis was associated with the stratigraphic break between Lower and Upper Wyloo Groups of the Ashburton Province, and has been variously linked to the Ophthalmian orogeny, late-orogenic extensional collapse, and anorogenic continental extension. Small spot PbPb dating of in situ baddeleyite by SHRIMP (sensitive highresolution ion-microprobe) has resolved the ages of two key suites of mafic intrusions constraining for the first time the tectonic evolution of the Ashburton Province and the age and setting of iron-ore formation. Mafic sills dated at 2208 ± 10 Ma were folded during the Ophthalmian orogeny and then cut by the unconformity at the base of the Lower Wyloo Group. A mafic dyke swarm that intrudes the Lower Wyloo Group and has close genetic relationship to iron ore is 2008 ± 16 Ma, slightly younger than a new syneruptive 2031 ± 6 Ma zircon age for the Lower Wyloo Group. These new ages constrain the Ophthalmian orogeny to the period <2210 to >2030 Ma, before Lower Wyloo Group extension, sedimentation, and flood-basalt volcanism. The ~2010 Ma dykes present a new maximum age for iron-ore genesis and deposition of the Upper Wyloo Group, thereby linking ore genesis to a ~21002000 Ma period of continental extension similarly recorded by Palaeoproterozoic terrains worldwide well after the initial oxidation of the atmosphere at ~2320 Ma. The Lower Wyloo Group contains, in ascending order, the fluvial to shallow-marine Beasley River Quartzite, the predominantly subaqueously emplaced Cheela Springs flood basalt and the Wooly Dolomite, a shelf-ramp carbonate succession. Field observations point to high subsidence of the sequence, rather than the mainly subaerial to shallow marine depositional environment-interpretation described by earlier workers. Abundant hydro-volcanic breccias, including hyaloclastite, peperite and fluidal-clast breccia all indicate quench-fragmentation processes caused by interaction of lava with water, and support the mainly subaqueous emplacement of the flood basalt which is also indicated by interlayered BIF-like chert/mudstones and below-wave-base turbiditic mass-flows.

Made available in DSpace on 2015-03-26T13:28:33Z (GMT). No. of bitstreams: 1 texto completo.pdf: 4018410 bytes, checksum: feed045553b762ef8c1ac9447d0f42b0 (MD5) Previous issue date: 2013-03-21 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This research work was aimed towards the geotechnical characterization of samples from iron ore rejects coming from flotation and magnetic separation processes, together with the addition of LD steel slag, in order to use these materials as components for base of paved roads. In order to reach such goal, this research work was also concentrated in studying techniques for the utilization of such materials considered as rejects of the iron ore industry, considering the use of mixtures from flotation and magnetic separation rejects combined with LD steel slag and local granular soils, in order to reduce environmental effects caused by conventional methods of storage of these rejects in tailing dams and pile rejects, generally disposed at the mine environment.The findings of the experimental program carried out through this research were based on the following geotechnical testes: characterization; compaction and CBR performed at normal, intermediary and modified compaction efforts; triaxial drained tests; resilient modulus tests; and sand equivalent test. Test results from granulometric stabilization techniques as well as those obtained from CBR and expansion tests, showed that the studied iron ore rejects are suitable for being used as subbase layers of flexible pavements, according to the "Design method of flexible pavements" from DNIT. Also, the laboratory testing program consisted of performing repeated load triaxial resilient modulus tests for these rejects and their mixtures. The best constitutive relationship was the one relating the resilient modulus and the bulk stress, M R = K 1&#952; K 2 . Finally, laboratory test results showed that these rejects and their mixtures are potentially suitable for application in pavement structures. / Este trabalho teve como objetivo a investigação em laboratório das características e propriedades geotécnicas (físicas e mecânicas) de rejeitos de minério de ferro (oriundos dos processos de flotação e concentração magnéticas) e escória de aciaria LD, com o propósito de inseri-los como material de construção em pavimentos rodoviários. Para tanto, nesta dissertação buscou-se encontrar técnicas de aproveitamento de materiais considerados como rejeitos dos processos do beneficiamento de minério de ferro, fazendo uso de misturas entre os rejeitos de flotação, de concentração magnética, escória de aciaria e cascalho, de forma a reduzir os impactos ambientais oriundos do seu armazenamento dentro da circunscrição da mina. Os resultados encontrados através do programa experimental realizado para a formulação desta dissertação basearam-se em um programa experimental com a seguintes ensaios geotécnicos: caracterização; compactação e CBR (Califórnia Bearing Ratio), nas energias de Proctor normal, intermediário e modificado; ensaios triaxiais drenados e triaxiais de cargas repetidas (módulo de resiliência); e, por ultimo, equivalente de areia. Os resultados da composição granulométrica assim como os resultados de CBR bem como suas expansões, indicaram que os rejeitos estudados são compatíveis para utilização como materiais de sub- base de pavimentos flexíveis, segundo o "Método de Projetos de Pavimentos Flexíveis" do DNIT. O melhor ajuste dos resultados de módulo de resiliência em termos de R2 foi o modelo que utiliza a primeira invariante de tensões, M R= K1 &#952; K2. Logo as misturas desses materiais apresentam potencial para serem utilizados em camadas de pavimento.

Abstract At least 30 gold deposits verified by means of one or more notable diamond drill hole results have been discovered in Central Lapland in the last 20 years, and these can be divided spatially into groups, between which the metal composition varies. The deposits contain varying amounts of sulphides and sulpharsenides as well as gold. Pyrite is the most common sulphide mineral in the gold deposits associated with volcanic rocks, and usually pyrrhotite in those associated with sedimentary rocks. The principal sulphide minerals in those connected with banded iron formations are pyrite and arsenopyrite. A separate group of formations consists of the palaeoplacer gold deposits associated with the molasse-like quartzites and conglomerates of Central Lapland. The iron oxide-copper-gold deposits of Central Lapland, which are a significant potential source of copper and gold, are mostly associated with skarn rocks at the eastern contact of the acidic intrusive rocks of Western Lapland and with skarn rocks occurring as interlayers in metavolcanic and metasedimentary rocks. The gold deposits that have led to actual mining activities in Central Lapland are Saattopora in Kittilä and Pahtavaara in Sodankylä. Apart from the Laurinoja iron oxide-copper-gold ore body in Kolari, copper concentrate has been produced from the Saattopora gold ore deposit and the Pahtavuoma copper ore deposit. Only one gold ore in Central Lapland is being actively exploited at present, that of the Pahtavaara mine, which was worked in 1995–2000 and reopened in 2003. The best starting point for successful gold ore exploration in Central Lapland can be achieved through a thorough knowledge of the deformation zones and their structures and alteration processes and the application of geochemical methods. Magnetic surveys can be of help in identifying and locating deformation zones of interest for exploration purposes and the majority of the associated shear zones and faults. Ore-critical zones usually feature graphite-bearing schists and iron sulphide-bearing sequences that can be traced by electrical methods and used as marker zones to verify the results of geological mapping. Geological, geophysical and geochemical techniques have been used in great diversity, and in particular till geochemistry and bedrock drilling have been methods by which the gold and copper deposits in Central Lapland have been discovered. A total of 7.6 million tonnes of gold and copper ores, including the Laurinoja iron oxide-copper-gold ore, were extracted in Central Lapland over the period 1982–2000. The resulting production of gold during this period was 10 800 kg, together with 21 000 tonnes of copper in concentrates and 4500 kg of silver. The gold and copper ores have been concentrated by gravity separation and/or flotation, since the ores so far taken into production has been of the free milling type. However, a substantial proportion of the deposits in the area contain copper, nickel, cobalt and arsenic as well, in the form of sulphides or sulpharsenides, so that the achievement of commercially saleable products calls for the use of different leaching processes. Deposits have also been found in Central Lapland that have consisted partly or entirely of refractory gold ore in which gold is lying in the crystal lattice of pyrite and/or arsenopyrite, the processing of which by the above-mentioned methods is not economic, as it requires pre-treatment by bio-oxidation or pressure oxidation in order to convert the gold to a cyanide-soluble form.

published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy